 Everybody, Dr. O here, we're moving on to myth number three. Fasting will eat up your muscles. First thing I have to tell you, muscle and lean mass are not the same thing. You certainly might lose some lean mass while you're on a diet. This is true of any diet, fasting or not. Number one, fat isn't just fat. Fat is somewhere between 13 and 16% lean mass because it has protein in it, cellular structures in it, et cetera. Even if all you lose is fat, let's say you get a DEXA scan. Some of that fat loss will show up as lean mass loss. Now, the thing to keep in mind is that you're carrying less you around. If you lose 100 pounds, maybe you will lose a little bit of lean mass because you're carrying less you around. Imagine strapping 100 pounds on your back, your lean mass is going to go up because you have to carry more of you around. Keep all those things in mind. The real question we're trying to answer here is, how long can you fast before you start to lose more lean mass than you absolutely have to? What I'm going to say here is that smart fasting won't eat up your muscles at all and I will explain why. Let's go ahead and dive in. What does the science say? One of the most important studies I've ever seen as a diet or as a nutrition teacher. A limit on the energy transfer rate from the human fat store in hypophagia. This study is going to tell us how aggressive we can be on any type of diet because it will tell us how much energy our body fat can provide each day. Hypophagia means when you're not eating as much as normal, energy transfer rate is saying how much energy can a pound of fat provide is basically what we're going to look at here. Here is from the abstract and I'll decipher it. A limit on the maximum energy transfer rate from the human fat store in hypophagia is deduced from experimental data of underfed subjects maintaining moderate activity levels and is found to have a value of 290 plus or minus 25 kilojoules per kilogram per day. In the next slide I'll make that calories per pound. Just so you know these underfed subjects, they lost 25% of their body weight. They were eating 1,570 calories a day, just so you know. A dietary restriction which exceeds the limited capability of the fat store to compensate for the energy deficiency results in an immediate decrease in the fat free mass. In cases of a less severe dietary deficiency, the fat free mass will not be depleted. What that is saying is once you know how many pounds of fat you have in your body and once you know how many calories those pounds of fat can provide, you know how much you need to eat. If your body can provide a certain number of calories, you have to provide the rest or you will start to lose lean mass. If you go on a diet that is too strict, you will immediately start to see a decrease in your fat free mass, which is everything in your body that's not fat. If you don't go on that strict of a diet, you should be able to lose just fat without losing muscle or lean mass on top of it. Here's the numbers. I did the calculations. You can take a look at them. I converted kilojoules per kilograms per day into calories per pound per day. This gives us a ballpark estimate of 29 to 34 calories per pound of fat. I usually stick with 30, so let's make it simple. Every pound of fat on your body can provide 30 calories. I do that because I err on the side of being less aggressive because I want to make sure you preserve every ounce of lean mass that you can. So cool. This is so important. We no longer have to guess how many calories we should be eating on a diet. We no longer have to guess how aggressive we can be with our fasting. This information is an absolute game changer. So let's go ahead and look at some real world examples. So I have four of them here, a 300 pound man with 40% body fat. That means he's carrying 120 pounds of fat on his body. A 150 pound female with 30% body fat would have 45 pounds of fat on her body. A 200 pound male, 12% body fat. He would only have 24 pounds of fat on his body. Then the last one was actually from my last DEXA scan and my last resting energy expenditure test. A 268 pound man with 32% body fat. That's where I was at that point. I had 86 pounds of fat on my body. All right. So 300 pound man with 40% body fat that gives us 120 pounds of fat. Let's take that times three, 3,600 calories per day. That's how much energy this person's fat can provide. His maintenance calories were 2,560 calories per day, which you'll see is way less than 3,600. So this person could do alternate day fasting. No problem. Should not be dipping into their lean mass stores at all because as long as their fat is providing that much energy, then why would your body pull from your lean mass? This person would have to be a heavy exerciser before they would ever reach a maintenance calorie number where I would be concerned about fasting with them at all. Can this person fast safely? Absolutely. I could do any of the fasting protocols I recommend, even the most extreme, which is alternate day fasting with zero calories on your fasting days. Now let's look at some gray area. Next person. 150 pound woman with 30% body fat. She has 45 pounds of fat on her body. 45 times 30 is 1,350. Her maintenance calories are 1,678 calories. So take 1,678 calories minus the 1,350 calories her body can provide, and we're left with 328 calories. So should this person do alternate day fasting or they eat zero calories on their fasting days? No. I'm definitely not saying they should eat 328 calories per day. I'm saying they have to eat 328 calories per day if they want to preserve lean mass. I know plenty of people with these stats that do alternate day fasting, they lose weight great, but they're probably losing a little bit of lean mass. Not a ton, especially if they're sleeping and their stress is under control and they're lifting weights. But if you want to maximize your fat loss while minimizing lean mass loss, this person should be eating 328 calories on their fasting days. So they would do the modified or hybrid fasting program I recommend where they eat, that on their fasting days they would eat 328 calories are in that ballpark, which is perfectly fine. Lots of people do alternate day fasting where they eat up to 500 calories on their fasting days. So is fasting safe for this person? Yeah, I wouldn't recommend the strictest alternate day fast and definitely not extended fasting, but they could do the hybrid alternate day fast. They could do the 5-2 program. They could do any of the time we should be feeding. So fasting perfectly safe will not impact their muscles if they do it smartly. Next one, 200-pound man, 12% body fat. That's only 24 pounds of fat, 24 times 30. This guy's body fat can provide 720 calories per day. His maintenance calories are 2,513. So take that 2,513 minus the 720 his body can provide. He needs to provide his body with 1,793 calories per day. Alternate day fast things off the table if he wants to preserve lean mass. I would recommend the 5-2 program, they're all at the table. I would recommend time restricted feeding in a 16-8 window. So in 8 hours every day he should be eating around 1,800 calories. He can eat less, but he'll lose more lean mass than he technically would have to. He can eat more and go on a slower diet and that'd be perfectly fine too. But that's the number he should shoot for. So you probably don't care about these people. Let me share one example of me and then we'll kind of look at how you could look at this. So a 268-pound man with 32% body fat. That would be 86 pounds of available fat, 2,580 calories per day could be provided by that fat. These calories 3,341 when I'm doing moderate exercise. If I'm doing light exercise it's down to 2,964 or sedentary is 2,587. So that's the number that I kind of look at here. On a day when I'm doing moderate exercise I'm eating. Those are my eating days. So can I still do alternate day fasting? Yes, because on the fasting days I'm just doing light activity or I'm sedentary. I'm sitting here, I'm working, I'm standing but I'm not doing a whole lot. I'm not exercising. I'm taking some walks. So I'm in that window where my body could, at this point, where my body could still provide the calories I needed every day. So I'd already lost 146 pounds by then, I was still using alternate day fasting. I'm leaning on this now and I'm still doing it but I just have to be really careful. Another thing I would note is generally when I am fasting I'm also on a low carb diet so I'm more fat adapted. So I think part of that means that your body fat can actually provide energy more efficiently as well. So at this point I'm at that gray area but what should I do? I should definitely not be super active on days when I'm fasting. I shouldn't be training on days when I'm fasting because my calories for those days would go too high. But in this situation fasting was still safe. So you need to go through the lesson where I taught you how to figure these numbers out for yourself. So basically what you need to determine is do you need to be eating? If you have enough body fat on your body you don't need to be eating and you can do alternate day fasting. If you need to be consuming calories then look at the modified programs or look at time-restricted feeding. But smart fasting will not eat up your muscles. And don't forget you can even build muscle while you're fasting. So when I lost my first 100 pounds 88% of it was fat, 12% was lean mass. And that lean mass really came from fat. I was getting stronger, everything was showing that I wasn't losing muscle while I lost 100 pounds. But then as I lost the rest, so when I got to 165 pounds of fat loss, I'd actually increase my lean mass by 15 pounds. This is documented by Dexascam. So not only can you fast and not worry about your muscles, you can fast and build muscles if you follow this program to the letter. So do you know what will eat up your muscles though? When you're on any kind of diet, fasting or not. Being on an aggressive diet without lifting weights. So I always recommend if you're worried about lean mass, then tell your body that it can't use lean mass for fuel. So get some resistance bands, take some walks, walk up and down the stairs. It doesn't have to be a lot, but use your muscles. So your body sees them as a necessity and not a potential fuel source. Okay, this is a super important myth and we now have busted it. I hope this helps. Have a wonderful day. Be blessed.