Hello and welcome to the webinar. Taking the pain out of nutrition calculations. My name is Georgia Woodsley, and it's a great pleasure to deliver this session to you.
So as a nutrition specialist and clinical lead for the obesity care clinic, nutrition calculations are something that I find myself doing every day in my working life. But it wasn't always that way, and I was the typical nutrition calculation avoider because maths is not my thing. I do not find maths easy.
But through seeing the benefits of doing nutrition calculations, through breaking it down, making it logical, I have now found a layer of comfort that enables me to be really accurate with my feeding recommendations, which ultimately improves my patient care. And that's what I'm hoping to give to you in this session. So we'll focus firstly on why we should bother in the first place, doing these calculations, why we would want to go further than just looking on the back of the bag of food.
We'll then dive into some specific calculations. So we'll think about energy calculations for weight maintenance. We'll think about the daily feeding quantity, we'll think about calculating the costs per day.
And in the day and age where the cost is going to be a big deciding factor for the pet owner, these calculations are actually really important. We'll then also look at how we can use nutrition calculations to compare two different diets. And then we'll turn to my favourite topic, which is of course weight loss, and we'll think about how we determine an ideal weight for our patient.
How we calculate an energy requirement now for weight loss, and some of the specific calculations that are useful when our patient has lost some weight. Now this might be purposeful weight loss, but it also could be unplanned weight loss, and both of those are going to be very useful, when we do the calculations to understand how much they've lost and how quickly that's happened. So let's think firstly about why we should bother with calculations in the first place.
I want to touch on the problem. I want to think about the good reasons to calculate and how actually we can gain hugely professionally from doing this. So the problem for me with calculations was always I, I just felt so under pressure.
It was such a spotlight that I particularly if I was doing this in front of the pet owner, it was actually really stressful. And like anything that needs lots of pieces of information, doing nutrition calculations can take quite a lot of time. So that can be difficult also.
And so, When we're dealing with lots of facts and figures, I was always so worried that I was going to make a mistake. Our mistakes happen, they just do. But we can put in failsafes, we can put in place things that are going to make this much easier.
And that's going to include stepping out. Take a moment, have some worked examples, have a spreadsheet that's going to make these calculations easy. Have a colleague check these numbers over.
There is no shame in getting that backup and using this help where it's needed because it is difficult and can be stressful. The other thing to do is to remember why we're doing this. Ultimately, it is for accuracy.
Now accuracy is going to eliminate any guesswork, and guesswork might mean that we've recommended too much for our patient, or we've not recommended enough. We might have made a recommendation that's unbalanced the diet and in really extreme circumstances we may cause a nutritional excess or deficiency. And by calculating the nutritional requirements and the daily feeding quantity, that accuracy is gonna take all that away.
All the guesswork is gonna be gone. Accuracy also allows us to treat pets as an individual. When we look on the back of the bag of pet food, we've got huge increments usually between the different feeding quantities that really aren't that helpful at the end of the day.
So by doing the calculation, we can have an amount for that specific patient, which again improves our outcomes and improves our patient care. By calculating, we get much better predicted outcomes. So we get to know that if we have calculated something, our outcomes should be what we hoped it would be.
And following on from that, that means that ultimately we can achieve our nutritional goals for each one of those patients. And so for me that is more than enough reason to get into it when it comes to nutrition calculations. And so the other things that I get from doing nutrition calculations is confidence, confidence from the knowledge that I know where those figures have come from and what they mean.
Confidence then from the familiarity of using these calculations. I get huge amounts of confidence from any backups that I've put in place, whether that's a cheat sheet, whether that's a spreadsheet, whether that's a colleague looking over my calculations and making sure that I didn't bring anything silly into the equation. Also, what this does for me is that it gives the clients value for money for my time.
And actually what this will allow you to do and to be is that trusted expert, that source of accurate nutritional information that I promise you pet owners can pretty much get nowhere else. They cannot walk into a pet shop and get this level of accuracy, get this level of certainty with that nutritional recommendation. This is where nutritional calculations play a vital part in the service and the care that we can provide.
Now, having said all of that, the nutrition calculation is only ever the starting point. And I really want to stress this, because I know in the past, in speaking to other people, people can become quite fixated on that number that you've worked hard to calculate, but every patient is an individual. And even if you calculate.
Whatever it is to the individual level, that patient will react slightly differently to the next one. And so it's only through monitoring and frequent monitoring that we know that we're actually getting it right, that our recommendation is correct. So for instance, for my, weight patients, unless I weigh my patient regularly, I don't know that I've actually recommended an amount of food that's going to bring about weight loss.
And if I haven't, and the client is following all my recommendations, then I need to adjust that recommendation. Similarly, if you're looking to reduce the serum phosphorus for your kidney patient, you will need to do repeated blood sampling to know that your nutritional recommendation is working to reduce that phosphorus content from the blood. And so although we are going to do these calculations, and they're really important, it is to stress once more that it's only through monitoring of that patient that we actually know if we're doing, doing it right and getting it right.
So the other problem that I want to say from the outset is that there is more than one way of doing just about all of this. We've heard these sayings, haven't we? There's more than one way to crack the nut, and there is, and if you go and look elsewhere, you go and read online, you are going to find many, many, many different types of calculations that you can use.
And so what I would strongly recommend is that you choose one, and as a practise, you stick with that. I am going to be talking within this session about the calculations that I use. These are the ones that make most sense to me, that I find easiest, quickest, and give me the best accuracy.
But you don't have to take my calculations. You can use others elsewhere. Just be consistent, I think is the key thing.
So let's think about how this all starts in a consultation or potentially in the hospital. And it's when a pet owner walks in and maybe you've not seen Sandy for a little while, and the owner proudly says, I've bought Sandy a new food. How much should I feed her?
And I'm looking to you for that quick, quick, how much do I feed? Now, of course, in my mind when I'm faced with this, I've probably never even seen this food before. I've never heard of it, let alone have any clue how many calories are in there or how many calories Sandy needs.
They've kind of hit me with this, and I need to do something. I need to do some calculations to work this out. So rather than panicking and flipping the bag over and going, well, this, maybe this amount should be fine, I'm going to confidently say, Give me a moment.
Let me calculate that for her. And at this point I'm probably going to take her bag of food, step outside the room and say I'll be back in a few minutes with the answer. So the first job when we're met with this question of how much to feed is to know how much energy our patient needs.
And we've got two major calculations that we can be using maintenance energy requirements and resting energy requirements. And depending on the situation, depending on the patient, you will be choosing one of these two calculations. So our maintenance energy requirement is for a moderately active adult, dog or cat.
It is in a thermo neutral environment, not fasted. It accounts for energy losses for obtaining food, digestion, absorption, and spontaneous activity, and maintenance energy requirements are used to maintain the weight. We're not looking for weight gain, we're not looking for weight loss, we're looking for to keep things nice and stable.
Now if we think about some of the things that are included in that list, what is moderately active? Ah, that's a difficult decision, where of course some dogs and cats will be more active than others. Not fasted.
Well, yes, we may meet patients that are not fasted, but we may also meet patients that have been fasted or have not been eating. And then accounting for energy losses for obtaining food. I'm pretty sure most of our pets that we meet don't expend a whole amount of energy obtaining food.
It's not like, say, a horse that would be grazing in the field that may travel and therefore expend energy. It's not like a cat having to feed itself by predation alone and going out and actually hunting. So although maintenance energy requirement isn't perfect, it is one of the useful calculations that we have.
The other calculation is resting energy requirements. Maybe this fits our patient better. So this is just for a normal adult, whatever normal might be.
Again, in a thermo neutral environment so not hot, not cold, in a stress-free situation. Interesting. That isn't always the case again for every one of our patients.
And this energy calculation does account for energy losses too, from metabolism, digestion, absorption and recovery. And so of course this would be very useful to us in certain situations. So what we typically do for patients that are generally well, you know, for Sandy, who's just come in for her booster, I would be looking at maintenance energy requirements for her.
For patients that are unwell. I would be thinking about using resting energy requirements, particularly if they're in the veterinary hospital. So for at home patients, MER for in the hospital patients, RER.
So let's look at our MER calculations, and there are three major ones that we'll be thinking about. So for dogs, we've got this top calculation, 95 to 130 times the body weight to the power of 0.75, and that's going to give you a calorie amount per day.
Now this range here, they're known as changeable coefficients, and what you need to do is pick a number somewhere between 95 and 130 depending on your patient. And I'll talk a little bit more about that later on. For cats, we've got a choice of two MER calculations.
If we've got a cat at a healthy, lean weight, then we'd use the top one, so 100 times the body weight to the power of 0.67 this time. That will give us a calorie amount per day, or if we have a cat with a certain level of overweight or obesity, we should be using a different calculation.
So this time it's 130 times the body weight to the power of 0.4 this time and again that will give us a calorie amount per day. And as you will notice, we do have exponential or exponent calculations here.
So you will need a scientific calculator, you will need to locate that exponent button. So where you see that little hat symbol, that's where you're going to press your X to the button on your calculator, followed by whatever the exponent factor is to get the calculation done. Don't worry, we're gonna walk through all of this as we go.
So yes, let's use an example. So we have Ollie here. He is a 30 kg dog, and I need to work out how many calories he needs per day.
Now my first question is, what coefficient am I going to use? Now let's look at this dog just for a moment. He's a Labrador, and I think that's probably all we need to know at this point.
So, Labradors, we know, of course, are prone to gaining weight and. Although this little chap is at a great weight at the moment from what we can see just here, we want to prevent him gaining weight in the future. So I'm going to be using the bottom end of the coefficient range, and so I've chosen 95.
So let's work the calculation through, so 95 times his body weight, which we know to be 30 kg, to the power of that little exponent button 0.75 will give us a calorie amount per day of 1,217 calories. Now at this point, I don't tend to round up or round down.
I let the calculator do its thing. But when of course we get onto an actual kibble in the bowl calculation, we are then going to start rounding up a lot more. So that's for a dog.
What about for a cat? So this cat here is a 6 kg Maine Coon, so she's a big girl, but she's nice and lean, so I'm going to use the lean calculation as the example. So in a very similar way, we take that 100 times by the body weight to the power of 0.67 this time, and that's going to get us a calorie amount per day of 332.
Excellent. Now let's take a look at our resting energy requirements calculations. So these are for our sick patients, these are for the patients most likely that are in our hospital.
This is where these calculations are most appropriate. And now, although we do have two different options, they are the same options for cat or dog, but you will see it depends on the body weight, depending on which calculation we're going to use. So if we've got a dog or a cat between 2 and 30 kg, we can use a linear equation, body weight times 30 plus 70.
Or if we've got a very tiny patient, so that's under 2 kg or one that's over 30 kg, then we use an exponential calculation again. So we have 70 times the body weight, and this is current body weight, just to stress to the power of 0.75, and that will give us a calorie amount per day to feed them whilst they're unwell in the hospital.
So let's take a look. We've got little Charlie here and so the first thing we look at is how much he weighs. So he's 28 kg, so we're going to use the linear equation for him.
So 28 being his body weight, times by 30, at 70. Sure you're all familiar with these, but I thought it's worth starting here, getting the basics, in their solid. So he would need 910 calories per day whilst he's recovering in the hospital.
What about Beau though? So Beau, German Shepherd, 76 kg, so it doesn't take any kind of expert to know that Beau is maybe above his ideal weight, but the hospital is not the place to get weight loss, and so we should be feeding Beau to maintain his current weight. So this time, because Beau is a lot bigger, of course, over 30 kg, we're going to choose the second RER calculation.
So we have 70. Times by his body weight, 76 to the power of 0.75 gives us a calorie amount per day for bow of 1,801.
And so in this way, using either MER or RER we can determine exactly how many calories that patient should need. OK. So now we move on to the energy content of the food that we we might want to choose for our patient.
So job number one, how much energy does my patient need? We know that, we've done that, tick. Job #2 is choosing the food that you want to feed.
Now maybe this is a food for recovery. Maybe this is a food for a specific purpose like kidney disease or pancreatitis. We will be making those food choices depending on that individual circumstance.
The next question that we need to answer is, what is the energy content of the food that I've chosen or potentially that the owner brought in. Remember Sandy and her bag of food. So how much energy, how many calories are in that food and where on earth am I gonna find this information?
Now the reason that this isn't easy is because the calorie content of pet food in the UK and in Europe is not a legal requirement. If you go to the US, they do have it on their bags of food, but here in the UK we don't. So we have to look at the analytical constituents that that pet food packaging is giving us.
Now, it might be that We have a product with a product book, and in which case we can look in our product book and it will give you the energy content, brilliant. Or if you wanted to, you could phone the pet food manufacturer. They will tell you for sure how many calories they have determined is in their food.
So in many different ways, but of course, you know, if it's not written on the bag and you haven't got time to phone the manufacturer, we're going to have to calculate that ourselves. So this is our next task. So we know that the calorie giving nutrients that we find in all foods come from protein, come from fat, and come from carbohydrates.
But when we take a look at our analytical constituents, and they may or may not appear in a nice little table like this, often not, they're just written, in line text, but you will notice that we've got protein and fat, but we don't have the carbohydrate content, which again is very annoying because we need that number. But again, it's not a legal requirement to put it on the packaging of pet food, so manufacturers don't do it. So again, we've got to calculate this.
So it's not straightforward. This is a two-step process. So we've now got to calculate that carbohydrate amount.
We also need to know what the moisture content is of the food. And again, it may not state that in the analytical constituents, particularly if it's a dry food. Wet foods and moist foods, they will state it, but dry foods won't.
So again, we could maybe, phone. Manufacturer of that food and ask what is the moisture content of this particular diet, or it is reasonable for all dry foods to assume that dry foods contain 10% moisture. And certainly from our calculations point of view, that is perfectly reasonable.
So, OK, we know now what the, moisture content is, we go ahead and calculate the carbohydrate content. And this is the way that we do it. So we take 100% and we minus off all the percentages that we see in our analytical constituents for protein, for fat, for fibre, for ash, and then the moisture.
We don't need to worry about minusing the percentage of calcium or magnesium or omega 3, they contribute so little. That they aren't relevant for these calculations, so just the fat, protein, fibre, ash, and moisture. So here's our example.
So for this particular food that I was looking at, so the protein amount, we can see, was 20.8%. So we take 100 minus 20.8%, minus 14.1% that came from the fat.
-1.8% for the fibre, 4.7% for the ash, and because we don't have a moisture amount stated, we're going to use 10% for moisture, and that gives us a carbohydrate content of this diet of 48.6%.
Brilliant. OK, we've worked hard to get here. Let's now go back to our, question of, well, how many calories are in this diet.
So now we have all the information that we need. And so we can use this information together and we can calculate the energy content. And I'm going to use and show you modified Atwater energy calculations for calculating a calorie content of food.
Now, as I said at the beginning, there's many different ways of doing this is online calculators, there's all sorts of other ways of doing it, but these calculations are relatively straightforward, so this is why I like them. So these are the formula that you will need, and what you can see here is we take the percentage of protein, fats, and carbohydrates, and we times that by a factor of either 3.5 or 8.5.
And that will give us a calorie amount per 100 grammes. So let's do the actual example. So for protein, first of all, our percentage of protein was 20.8 times by 3.5, this is the factor.
And that gives us 72.8 calories per 100 grammes that comes from the protein in that food. We do the same for fats, so 114.1 times by 8.5 this time.
So calories that come from fat are almost double that that come from protein and carbohydrate, which is why this factor is so much higher. So from the fat, we get 119.85 calories per 100 grammes.
And finally from that carbohydrate amount that we worked really hard to find, 48.6% times by 3.5 again, gives us 170.1 calories per 100 grammes.
Now we are still after what is in this food, so we add all these totals up together to hopefully give us finally a calorie content of this food at 363 calories per 100 grammes. Excellent. But we're still not there.
We still don't quite know how much food to put in the bowl, do we? So next we have to use these figures that we've found to calculate the feeding quantity. So here it is all written out.
This is for Ollie, so we know that he needed 1,217 calories per day. We then went ahead and looked at the food we'd chosen and worked out the carbohydrate content so we could ultimately work out how much the energy content was of his diet. And that was 363 calories per 100 grammes.
So now let's use this information to determine how much we're going to put in his bowl. And we're gonna look at dry food only to start with because we can layer up and think about wet food in a moment. So to understand how much we put in his bowl, we're going to take the calories that he requires, and divide that by the calories that are in the food, and times it by 100.
So we get 1,217, that's what we calculated he needs per day. Divide that by the calories in the food, we calculated that at 363 times by 100, gives us 335 grammes of food that we're going to put in his bowl. Now at this point I'm gonna call a sense check.
So does that make sense? And I think it's really important to ask yourselves that once you have a feeding quantity. Have I calculated something in error?
Have I calculated that I want to feed Charlie, sorry, Olly here, 3000 grammes a day? Because surely that couldn't be right. And if my calculation came out at 35 grammes, well, that surely can't be right either.
So just ask yourselves when you get that feeding rack, does this make sense? Does it seem right? And I think in this case, 335 grammes feels very reasonable to me.
I am happy that my calculations are correct. OK. Well, life is never simple, is it?
Because, Ollie's owner here decided, well, actually I quite like to feed some wet and some dry, and I'm gonna use different brands. So there is no easy way of being able to determine that. So we go ahead and we can calculate this also.
So job number 1 was calculating the energy content of the dry food. We've done that. Brilliant.
Job #2 is doing the same thing for wet food. And as the calculations have given us initially, we find the amount per 100 grammes. But our wet food comes in a tin.
Doesn't it, of course, or a pouch or a sachet, and it will have on the back of that product, how many grammes are actually in that tin. So we need to go ahead and do an additional calculation to know how many calories per unit. And that's really gonna help us keep the accuracy.
And work out a good feeding amount. So for this, example here, my tin is 400 grammes. So I take my calorie amount per 100 grammes and times it by 4, and that gives me 440 calories per tin.
Excellent. All right, next step is to take that energy requirement that we've already calculated. And I'm going to take away the amount that I want to devote or the owner wants to devote to wet food.
So whether that's a whole tin, but whether that's a half tin, I kind of try not to divide it up any less than that because we start losing our accuracy at that point. So, in this example, we're going to be feeding one whole tin and then the rest of the calories in dry food. So we take the energy amount that we worked out, his energy requirements, then we minus the calories that are in that full tin, that whole unit, and that leaves us with 777 calories for which we're going to feed him in dry food.
So then we go ahead just like we did, in the previous example, we take those remaining calories. We're going to divide that by the calorie content of his dry food times by 100, and then we should know how much wet and how much dry. So looking at the example, he I had 777 calories left to feed him in the dry food.
We calculated the dry food as having 363 calories in there. Time is by 100, gives us 214 grammes. And so again, To putting all this together, that means that we're going to feed Olly 1 full tin plus 214 grammes, and that's going to fulfil that energy requirement.
And sense Check once more. Does that feel right? Yeah, I think it does.
It. Certainly less than dry food only, which you would expect. It doesn't feel like 10 tins and a sort of wild amount like that.
So again, I'm pretty happy with my sense check that I've calculated something reasonable for my patient. OK. Now, like most pet owners, the pet owner is unlikely to give that in a full amount.
Just dump it down once in, once in the middle of the day. Pet owners will want to know how do I split up this daily amount that you've now worked out for me? So let's just think about it in terms of dry food, just to make our lives a little bit easier, though of course, if we've got a full tin of wet food, I'd go, well, let's do half in the morning, half in the evening, or a similar example.
And really it's because dogs and, we'll come on to cats in a moment, like to eat more than one meal a day or should be fed one more meal a day, because if otherwise, if you're like a Labrador and you've got to wait 59, sorry, 23 hours and 59 minutes and 30 seconds for your next meal, that's an awful long time to wait for food. So we should break it up and we should probably save some for treats to give us rewards also. So that's just what I wanted to touch on for a moment.
So most dogs happy to eat twice a day, and that fits in with pet owners' lifestyles, typically, but we should also set some aside, as I say, to give us rewards. So if we've got 335 grammes to play with, we've kind of got quite nice numbers here, actually. And so So what I'd do is I'd separate the 35 grammes to give as a reward portion.
And then the rest of the food we can divide up in those two meals, meaning that Ollie is going to get, 150 grammes per meal. Nice, simple, let's keep it easy. Cats are a little bit of a a different kettle of fish because actually cats would like to eat up to 16 times a day.
It's not necessarily practical, but that evidence is there. And actually I was lucky enough to have a microchip activated food bowl that fed back to an application on my phone and told me exactly how many times a day my cat liked to eat, and this is her chart. You don't need to see the detail because what it's showing you, each of these green dots is a feeding occasion.
And you can see she's back into the bowl quite frequently throughout the day. She tends to cluster feed, and this is for many cats actually how they want to be fed. So we might want to think about something slightly different for cats and maybe feeding them up to 12 times, up to 5 times a day.
So taking a daily allocation of something like 60 grammes, and that would give us 12 grammes per meal. And although an owner's not going to want to get their scales out 5 times a day and weigh out 12. So maybe let's use something like these timed feeders that are going to automatically have food available at multiple times throughout the day, allowing cats to eat little and often, stopping them from stopping all their food in one big go, but actually kind of aligning with how cats want to feed.
I think that would be really nice. OK. Now, we've worked pretty hard so far.
We've got an energy amount, we've got a feeding amount, but your owners are still going to ask, well, how much is that gonna cost me? So we should go ahead and work that out for them too, because this is going to be quite influential. Now.
On the face of it, when you are recommending a big bag of food, they will only see the price tag. 82 pounds, that's loads. And you know, it does sound like a lot of money.
So what we need to do is break it down, and this is why this all takes so much time. So we need to gather information about what the owner currently feeds. So we need to include the costs of the main meals, the treats of the human foods that they might give, of the scraps they might have, of any chews, and then put all of this in perspective in comparison to your dietary recommendation.
So step one of this is to have the amount in the bag in grammes and divide that by the daily ration, by the that quantity that we're putting in the bowl, and that will tell you and the owner how long that bag of food is gonna last. So, continuing on from where we were. With Ollie.
So we've got a 12 kg bag here, so that of course is 12,000 grammes. We wanted to feed him 333 grammes per day. So the 12,000 divided by 335 gives us that this bag will last 35 days.
Excellent. Still doesn't tell us how much it's going to cost though. So we move on to step two, which is taking the price of the food.
Dividing that by how long the bag's gonna last, that will give us a cost per day. So it's 82 pounds for the full bag. This is gonna be fed and it's gonna last 35 days.
So that means it's gonna be 2 pounds 30 a day. And if we're talking about, a highly specialised therapeutic diet, which these costs probably reflect, that is way less than that owner's morning coffee. I don't know what's happened to the price of coffee right now, but I feel like I'm paying over £4 for coffee pretty much every time I go.
So 2 pounds 30, when we think about it in perspective, isn't actually that bad. And particularly if you can compare that to what the owners were feeding, often they, you will find that you may have even saved the money. But because it's got this big price tag, we have to break it down for them because it will feel like an awful lot for food.
OK, now I just wanted to pause at this point and kind of give you this in summary. It's my little cheat sheet to remember the steps, remember the stages, kind of bring it all together. So choice number one, when we meet a patient and we want to know how much to feed us decide are we going to use MER or RER.
Then we go ahead and calculate the energy. So here's all those calculations written out. Then we have to choose our food, and then we calculate the energy content of that food.
Step number 1 being finding the carbohydrate content, step number 2, using modified Atwater calculations to give us that energy content, and then we can go ahead and create that daily feeding quantity by taking the calories that we need, divided by the the. Calories in the food by 100, gives us that amount to put in the bowl. And then we split the meal up, depending on how many meals that cattle dog may wish to have throughout the day, and then we work out the costs per day.
Step number one being working out how many days that bag of food will last. Step number 2, working out the cost. Per day.
And if we can, comparing that to what either what they're currently feeding, or to that daily coffee that the owner might be buying. And in this way, hopefully, we can get them relatively quickly, that piece of information that goes from, I bought this new food for Sandy, how much do I feed to this is how much you're going to feed, and this is how much it's gonna cost you. Brilliant information to give to your pet owners.
OK, now I said at the start I would talk about comparing diets and how nutrition calculations are really useful for doing this. Now, what this allows us to do is calculate things on an as fed basis. We don't need to worry about on a dry matter basis, we don't need to worry about taking the moisture out and all that sort of thing.
This is for me, the simplest way of making these decisions. So this often occurs where we have choice of diets. Maybe it's two choices of diet you have in practise, maybe it's the owner trying to decide between two different diets.
And ultimately we're wondering, you know, which is better, which would be the better choice. Maybe we're looking for which has most protein. Maybe we're looking for a diet with the highest or the lowest carbohydrate content.
Maybe we'll. Looking for a diet with the lowest fat, maybe we're looking for a diet with lowest phosphorus. There are so, so many questions that we can ask, that we can use the same types of formula 4 that's going to get us that good answer and the comparison of these two diets, because nothing is as it seems when we're looking at the food packaging, and I think that is the major issue.
Now to do this, we compare diets on a mega calorie basis or MA. And a mega calorie is just 1000 calories. That's all it means.
But it is a it is a way of levelling the field of truly calculating a good comparison, and an accurate comparison, comparing apples with apples, that's what we're aiming to do. Or food A and food B. So the question that I'm gonna use as our example is which of these diets has the highest protein content?
And that's because I want to feed a higher protein or as high protein diet as I can for whatever reason, to this 4 kg cat. So. Job number one is locate the product information.
Now we know that's going to be on the back of the bag. We need to identify the nutrients that we're interested in. So in this case, it's protein that we're asking about.
So in that analytical constituents, it will tell me that information about the protein amount. And then I need to calculate the energy content or find that energy content of the food per 100 grammes. Now we've just known how to do that.
We've done that already. You can phone the manufacturer, you can look in a product book, wherever you get that information, you will need it to be able to do this. And so these are the steps to calculating something on a megacal basis.
Our first job is to convert that percentage of nutrient to 1 grammes per 100 gramme. Now, those calculations should be easy because 100% is of course going to be the same as 100 grammes. The numbers are the same.
So if it's 20%, it's going to be 20 grammes. If it's 70%, it'll be 70 grammes and so on. Then we need to calculate the nutrient that we're looking at per calorie, per one calorie that's in that diet and then convert it to a mega cow.
That's how we flatten it, that's how we compare across the board. And we actually do these in combination, as you'll see in a moment. So diet A has 36% protein in it.
That's what it will state on the back of the bag. And when we've either calculated it or found it, we will know that this this food contains 344 calories per 100 grammes. Now we're comparing it to diet B.
So when we look at Dit B, the protein amount in those analytical constituents say it has 34% protein. And again, once we've got the calorie amount, we have a different calorie amount because most foods are going to be different from each other, 303 calories. So we've got a lower calorie product in product B.
So let's compare these on a megacal basis and here are the calculations that we do. So step number one was to convert the percentage into grammes per 100 gramme. So we get 36, it's 36%.
And therefore, we've got 36 grammes of protein per 100 grammes of this food. So 36. Then we divide that by the calories in the food.
This is how we find the amount of nutrient per calorie. And then we times it by 1000, and that's how we get a megacal amount. And so per megacal we have 104 grammes of protein.
You might think, OK, great, well, what does that mean? Well, let's do that with now product B. So product B has 34% of protein, so 34 grammes per 100 gramme.
Divide that by the calories that we have in this diet. This time it was 303. Apologies.
I've just spotted that I've written 304. Slightly see errors happen. This is, this is just what happens.
I have spotted it. I would go ahead and correct it if I could. But let's carry on because it's, it's very, very similar.
Times by 1000, because again we're using a megacal as our comparison, and this time we have 111 grammes of protein per megacal. Now hang on a minute, on the back of the bag, it said diet A was 36% protein, Dit B was 34% protein. So surely diet A has more protein, but in fact it doesn't, and it's only through calculating it per megacal.
And really levelling the playing field that we can see that actually it's product B that has the highest number or highest quantity of protein. And so when we're making the decision, well which diet contains the most protein, it is going to be diet B. OK, and so I hope that that is going to be really useful to you, so that you know, rather than just looking on the back of the bag, we can get some good comparison information.
OK. Now, that is great if all we're doing is comparing diet A with diet B. But what if we have a situation where the amount of calories that we may feed might change?
So here's my question, and this is, of course, one that I will meet and you will meet too, when you're doing weight loss. So my cat in front of me, my patient needs weight loss, but it's a senior. And so I'm really worried about feeding it a weight loss diet because of the phosphorus that might be in it.
So, let's have a think. Diet A is a senior diet. So it contains 36% protein, it's got 10% fat, and the phosphorus content is 0.8%.
Calories in this food was 344.5 per 100 grammes. These are all things that I've done in the background.
I've worked. All of this out to arrive at this place. If the phosphorus amount isn't stated in the analytical constituents, you can look in the product book, you can phone the manufacturer, you can get that piece of information.
So we need to do a bit of back work. So this is what our senior diet looks like. But because I know that this, my cat would benefit for some weight loss, I would really like to feed it a weight loss diet.
And the problem with weight loss diets is, is that they're often high protein, and a high protein diet is going to mean high phosphorus. And as you can see from the comparisons, we've now got a higher phosphorous diet. It is now 1.13% phosphorus.
So. Is it going to be safe to feed a weight loss diet? This is the question that I'm asking myself, and I can, look at the phosphorus content of both diets using a megacal basis to make that decision for me.
So this is how we do it. So we are just comparing phosphorus levels first of all. So just as we did before, going to level the playing field, look at everything on an MA basis.
So in diet A, our senior diets, we had 0.8% of phosphorus. So just as before, we take 0.8, divide that by the calories in the food, times by 1000, gives us 2.32 grammes of phosphorus per megacal.
OK. We do the same with our weight loss diets, so now we've got a higher amount of phosphorus, 1.13.
We divide that by the calories in the food again times by 1 1000 to get it in megacal, and we get 3.72 grammes of phosphorus. So on the face of it, we still have what we probably suspected was that diet B, being the weight loss diet and higher in protein, is going to have more phosphorus in it.
However, When we are feeding a cat for weight loss, we're going to be feeding a calorie restriction. And our senior diets, they're not balanced for calorie restriction. And so we cannot and should not use them for weight loss.
So if we want weight loss, we really should be only using our weight loss products. So if we're feeding for maintenance, and we're doing that for diet A because that's all we can safely do is feed for maintenance, the cat would need 268 calories. But we want weight loss, and I've done those weight loss calculations, which will come to a little later on, and determined that the weight loss calorie amount was 142 calories.
That's what we would be feeding if we could do what we want to do and feed our senior cat a calorie restriction, and that would have to be from diet B. So, to work this out and to actually know how many grammes of phosphorus our patient is gonna consume, we've got to do an additional step now and convert the energy intake to Megacal, again, flattening the playing field, getting everything in the same unit so we can compare. So we have that 268 calories that that cat needs per day for weight maintenance, divide by 1000 and that gives us 0.268 megacals per day.
The same with the weight loss amount, so. 142 calories is what's going to get us, actual weight loss. And then we go ahead and calculate the phosphorus in the food that our patient's gonna eat.
So we take the phosphorus amount in the food per megacal and we divide that by the mega cos our patient is gonna need per day, and this is what we get. So 2.32, that was that was how much was in the food.
We divide that by the mega cows that the cat needs to 0.268 gives us 0.62.
For Diet B, our weight loss diet, we do the same thing. We take the amount of phosphorus per megacal. We divide that by the mega cows per day that our cat's gonna receive, and that cat is going to eat 0.53 grammes.
So to answer our big question, we want to feed our cat a loaf. Phosphorous diet, and we want to give it weight loss. We're worried that it's not gonna be safe enough, but through this calculation, we can tell that actually when we're feeding for weight loss, the amount of phosphorus intake that our cat is gonna receive is going to be very similar and in this case lower.
Than if we were feeding them a senior diet where a phosphorus restriction is usually worked in, and so that's how I have certainty that I can safely go ahead with weight loss, ensuring that I'm also giving a slight phosphorus restriction. I hope that all made sense because this is a way that using Megaal makes it really easy to compare these two diets. OK, now I said I was going to take the pain out.
I hope I haven't put a little bit of pain back in with all of that, but hopefully these steps will help you get there. OK, so moving back just as we finish, to something a little bit more straightforward but nonetheless useful. So it is determining ideal weight.
And this is genuinely something I will do multiple times per day. And it's when we meet a patient like Sydney. So Sydney in this picture weighed 36 kg, and we determined he had a body condition score using a 9 point system of 7 out of 9.
So my question was, well, what's his ideal weight? Why does that matter? Well, it matters because we're going to be feeding Sydney for the weight that we want him to be, and that's his ideal weight.
And so up until this point, we've talked about using the current body weight of our patient. Now we're going to be thinking about ideal weights for the rest of this session. So we needed to know what is his weight, we need to know what his body condition score is, and using those pieces of information, we can determine his ideal weight.
Now to do this, we need another set of calculations, and here they are. So he has a body condition score of 7. So we're going to be using this particular calculation.
So here we are. We have to reach that ideal weight, we take his current body weight. Oh, excuse me, that current body weight of 36 kg.
We divide that by 1.2, as it says in the calculation, meaning that he should be 30 kg. And so, of course, at 36 kg, we know Sydney needs weight loss.
And that's how we then can go ahead and calculate a feeding quantity. So, as I say, we have so far been talking about calculations for current weight. Now we're talking about calculations for weight loss.
And so just like there, there are others, there are many ways of doing this. You will find lots of different examples out there in literature, on the internet, so bearing with that, again, choose the one that you want to use that you're comfortable with and stick with it. Be as consistent as you can.
Now just to make life difficult, if you start using these calculations for all different foods, weight loss foods that you come up with, you will very quickly discover that different food manufacturers will use different energy calculations and they will have their own. For doing that. I am only going to show you one example of calculations that we can use.
So here they are. So let's just digest these for a moment. So we have energy calculations for weight loss in dogs.
And again we've got some changeable coefficients and then the energy for cats for weight loss. So for dogs, first of all, you can see that we've got a different equation depending on if we've got a male or a female, whether they're intact or whether they're neutered. So this is a good level of individualization that we can apply here for our patient.
For cats, we've got a choice between an exponential calculation or we've also got a linear equation that we can use. So it depends which you want to use for your patient. Neither is better than the other, they are just different ways of doing it.
So let's take a little example. This is Bertie. Bertie is a neutered male and he currently weighs 13.1 kg.
And through body condition scoring and those initial calculations I showed you, his ideal weight was determined to be 8.3 kg. So getting your scientific calculator out once more, we do his energy calculation.
So, firstly, he's a neutered male. So we need to use the neutered male calculations. So we're going to use the exponent of, sorry, the coefficient of 70.
So we do 70 times by his ideal weight this time because we want to feed him for the weight that he should be with the food that I'm going to choose. To the power of 0.75, and that gives us a calorie amount per day of 342 calories.
Excellent. Step two, just as we did, for weight maintenance, is deciding on a food and how much we're going to feed him. So, let's get up our instructions.
So when we decide to do that exactly the same as we did before, we take the calories that he needs per day. We've just calculated it. Divide that by the calories in the chosen food times by 100, and that will tell us how much to put in Bertie's bowl.
So in Bertie's case, I'm after weight loss, so I've chosen a weight loss product here. I've chose a product for small dogs. Again, this is great individualization that we're getting here.
And this food is 270 calories per 100 grammes. So let's work the calculation. 342, that's the calories he needs for weight loss, divided by the calories in the food, times by 100 means that little Bertie here is getting 127 grammes per day.
But remembering, firstly, sense check, does that feel right? And secondly, this is only ever your starting point. And I haven't mentioned this for a little while, but it is with every calculation just where you start.
Be prepared to dynamically change that feeding amount depending on the outcome. OK, we are nearly there, I promise, but these are some of the useful calculations that I use in my weight clinics because they give the owner a really good understanding of what's going on with their pet. So this is little Dora.
Dora has just started on her weight loss journey. At the start, she weighed 12.3 kg, and now she weighs 11.9.
And we're right back to primary school maths with this one in terms of deciding how much she's lost, but we also would like to know how much she's lost in terms of percentage, because that actually will tell us a lot more information. So of course, to work out in kilos how much she's lost, we take the weight that she was last time and we take away today's weights and that gives us 0.4 kg.
Well done, Dora. But the owner at this point will look at you and go, is that good? I is 0.4 a lot?
Is that not enough? Is that too much? Well, this is when we use the percentage to make much more sense of that.
So we take the weight lost, that we, we've just worked out. We divide that by the weight that she was last time, times it by 100 because we're talking about a percentage, and that will tell us how much she's lost. So, we take the 0.4 that she's lost.
Divided by the weight that she was last time, so that was at the start of her journey in this case, times by 100 means that Dora lost 3.25%. We'll come on to how good or not that is in a moment.
And we can do a very similar thing. When we're talking about how much weight loss a dog has lost throughout its weight loss journey. So this is Mimi here, we can see that she's done exceptionally well with her weight loss.
So we think about the total weight loss. Since the first visit, and we put that in a percentage, and then we should average it out per week. And just like the previous example, weight loss per week is a really good, or the percentage per week is a really good measure and that we can talk to owners about.
So just like before, we take the start weight and take away the end weight, that will give us the total weight loss. Then we take that total weight loss divided by the weight she was at the start times by 100 to get our percentage. So here is the worked example, and ultimately we end up with Mimi losing an incredible 38% of her starting body weight during her weight loss journey.
And again, an owner might go, well, was that too quick? Was, was that fast enough? Was, you know, where, what, what was our expectation around that?
So if we think about this in terms of percentage per week, so we've got the percent that she's lost, 38%, she's done amazing. Divide that by the number of weeks this took, and in actual fact, in this case it was 52 weeks. So nice and easy, we divide that percentage lost by the number of weeks it took, gives us an average per week of 0.7%.
Now remembering Dora lost 3.25%, why does all this matter? Well, it's about safe limits and our expectations.
So you may have read in literature that we can expect 1 to 2% of weight loss per week from our weight loss patients when they're fed a correct diet. But this figure came from colony studies, and of course, that environment in a money is very controlled, and it's quite sterile, isn't it? We don't have pets, as in we don't have pet owners and neighbours that feed them over the fence and the groomers and the nice people out on walks, you know, so we have to adjust our expectations in terms of what we see with pets.
Now, when we look back at the 20 years that the weight management clinic, or now known as the obesity care clinic, has been going. Our patients, remembering they're all pet patients, lost at an average of 0.8% per week.
So if we think back to Mimi, she'd lost at 0.7% per week. She's almost bang on average.
So I would say to that owner, that's awesome. That's, you know, that's perfectly fine. In fact, I'm very, very happy with that rate of weight loss.
But what about the safe limits and thinking back to Dora? So in terms of safety, the dogs can lose up to 3% per week, cats can lose up to 2% per week safely, and we would like them to get over 0.5%.
However, it really depends on how much. Dora, therefore had lost that weight. So if she'd lost 3.25 in one week, oh, that was going some, and we're now getting up to that limit where I'm feeling uncomfortable.
However, if she'd lost that over 2 weeks, that would be a really, really nice rate of weight loss and well above the average that we typically see in pets. It's very rarely an issue though that we get pets losing too fast. What is much more common is that we get pets losing maybe a little slower than we'd like.
However, and you'll hear me say this, if you ever, see me in a consult room, weight loss is weight loss, and I'm happy. I'd like to aim for 0.5% per week, but it's not essential, but staying in those safe limits.
So, and that is it, and I hope I haven't pickled too many brains with all those calculations. What I really hope is that I've given you some really good logical worked examples that you can now use. So remembering the reasons why we're bothering is just so important.
Ultimately, it improves patient care, doesn't it? It is worth. Taking your time with these calculations.
And if you can do some pre-work or work ahead, absolutely go ahead and do that. Step out of the room if you need to, bring all the stress down. Don't be under the spotlight because that's when more more mistakes will happen.
Definitely get someone to check over your numbers. I particularly need that clearly, having made a mistake in this presentation. And then what this will do is allow you to give accurate information and be that trusted expert, delivering excellent nutritional information to your pet owner that I promise they won't find elsewhere.
I really hope you've enjoyed this webinar and thank you so much for listening.