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You’re about to start a weight loss diet. 

You know you need to eat fewer calories than you burn. 

You know roughly how much you need to eat every day to lose weight. 

Maybe you even have a meal plan mapped out. 

But there’s still one question you haven’t been able to answer: how long should you stay in a calorie deficit? 

If you poke around online you’ll see different theories about the “ideal” length of time you should stay in a deficit before giving your body a break.

Some say you should diet no longer than 12 weeks. 

Others say you can diet as long as you want. 

And others say you should only stay in a deficit for a few weeks at a time before taking a diet break, giving your body and mind a breather, and then enduring another bout of dieting.

Who’s right? 

Well, here’s the truth of the matter:

How long you should spend in a calorie deficit boils down to how fast you can lose fat without losing muscle, and this depends on how much fat you have to lose and how lean you want to get. 

So, instead of giving you a one-size-fits-all answer like “12 weeks,” I’m going to show you how to decide exactly how long you should stay in a calorie deficit to reach your goal weight. 

Let’s start by looking at how fast you can lose fat without losing muscle. 

Press play and let’s dive in!


2:49 – How long do I need to be in a calorie deficit?

6:14 – How do you calculate how much fat you can lose before you lose muscle?

16:51 – How long should i stay in a calorie deficit and when should I take a diet break?

23:31 – How do you do a diet break?

Mentioned on the show: 

Legion VIP One-on-One Coaching

What did you think of this episode? Have anything else to share? Let me know in the comments below!


Hello. This is Michael. Michael Matthews, and welcome to the Muscle Life Podcast. See, this is how I entertain myself these days. This is what it’s coming to. I’m going full Howard Hughes, sitting in my little bedroom in my basement, which has become my podcast recording studio. It actually has pretty good acoustics, so I am going to make a little proper.

In this room as opposed to a chair in the corner that I’m sitting in a metal chair. I will add not sure why we have metal chairs, but we do. We have a metal chair in here and I have my laptop on my lap, and I’m holding a mic that I’m speaking to you through. See high class. Here at Casa Matthews, but hey, it gets the job done right?

And what is today’s job? Well, we’re gonna talk about how long you should stay in a calorie deficit for, this is something that I get asked about fairly frequently and have gotten asked about since the beginning, since I entered the fitness space, whenever that was, 2012. so and so. It’s one of those perennial questions that I have spoken about and written about here and there.

I definitely have an article dedicated just to this, but I don’t think I’ve done a podcast episode dedicated just to this. I may have addressed it in a q and a some time ago, but I’m still getting asked it fairly often, and so I figured, Hey, let’s put an episode out there on just this.

So how long should you spend in a calorie deficit? Well, that depends on how fast you can lose fat without losing muscle. That’s the key, right? That’s what we wanna do. We don’t just want to lose weight. We wanna lose fat as quickly as possible, while at least maintaining the muscle we have, if not gaining muscle.

Right? And our ability to do that depends on how much fat we have to lose and how. We want to get. So it depends on how fat we are to start with and how shredded we want to get. And you know that you can lose fat very quickly through crash dieting. Of course, you could just starve yourself, eat 500 calories a day and move around a lot.

You’re gonna lose a lot of. Fat, but you’re also gonna lose a fair amount of muscle. And that’s why my advice is always to use as aggressive of a calorie deficit as you can before the wheels start to fall off. So be as aggressive as you can while still being able to maintain your muscle and your sanity.

And there is research that helps us understand how to do that. For example, research shows that there is a limit to how fast your body can. Body fat before it has to start breaking down muscle for energy, and that’s why crash dieting is no good in terms of muscle retention. Your body’s gotta get the energy it needs from somewhere and it will turn to muscle if it needs to.

A study that is particularly useful here was conducted by Seymour. Alpert over at the University of New Mexico, and what he did is he looked through previous research involving different sizes of calorie deficits and he concluded that the human body can extract energy from body fat at a rate of about 30 calories per pound of body fat per day.

30 calories per pound of body fat per day. So let’s say that you are a 200 pound. And, uh, I guess we’re gonna say you’re a 200 pound guy and you’re at 10% body fat. You’re lean, you’re big, you’re muscular. That means that you’d have about 20 pounds of body fat on your body and that you could extract, or you could burn up to about 600 calories per day, 20 times 30 from the body fat before your body would have to look elsewhere.

Meeting its energy needs. And so what that would mean then is you could maintain a 600 calorie daily deficit and not lose muscle so long as you do other things, right? Right. So long as you eat enough protein and you get enough sleep and you manage your stress properly and you train properly, but if you’re doing those things, Correctly, you should be able to maintain about a 600 calorie deficit per day and not lose muscle.

At least not have that drive muscle loss. That said, though, if you were to go with a larger deficit, if you were to bump that up to 800 calories, you would almost certainly lose muscle or accelerate muscle loss. So if you take that daily number, You can then multiply it by seven to get a realistic weekly fat loss goal.

So in this case, of the 200 pound dude at 10% body fat, seven times 600, 40, 200, and then you divide that by 3,500, which is roughly the number of calories that’s in a pound of fat. To find out how many pounds of body fat you could safe, Lose per week. And that gives us about 1.2 in this case. So if you’re a 200 pound dude, 10% body fat, you should be looking to lose around a pound of body fat per week, and you should set up your diet accordingly.

Now, let’s run those numbers for somebody who has a much higher body fat percentage. Let’s take someone who’s 250 pounds and 40% body fat, right? So first we’re gonna find out how much body fat they have by multiplying their weight by their body fat percentage. So here we have two 50. Times 0.4 times 40% equals a hundred pounds of fat.

So they have a lot of fat to lose. Now we’re gonna multiply their total fat mass by 30, uh, which is, as we remember, Alpert’s equation, to find out how many calories of fat this person can conceivably lose per day. We’ll see if they can really get there with dieting, but theoretically this is how much fat they could lose before they start to lose muscle.

So 100 times, 33,000, 3000. That means. They could, theoretically, they could potentially maintain a calorie deficits of about 3000 calories per day without losing muscle. That basically means not eating at all or being fairly active at eating like 500 calories per day. This makes me think of protein sparing, modified fasting, for example, where you’re really just eating protein four to 600 calories a.

And maximizing fat loss, and you’re using the protein to try to drive that muscle retention, and you’re also using this physiological phenomenon or this physiological mechanism to your advantage if you have a lot of fat to lose. Now, if we wanna look at how many pounds of fat this person could realistically lose per week, then of course you would multiply that daily calorie deficit by seven.

So we have 3000 times seven, 21,000, then we divide the 21,000 by the amount of calorie. In a pound of fat, which is about 3,500, to find out how many pounds of body fat this person could lose per week. 21,000 divided by 3,500, and we have six. We have six pounds of fat loss per week that this person could theoretically lose without losing.

Any muscle to speak of and you can find evidence of what sounds like an extreme weight loss protocol like that in the literature. The most extreme case, I mean truly is extreme that I can think of off the top of my head was a case study I saw where a guy started at about 400 ish pounds and he ate no food for a.

This was medically supervised, so they gave him intravenous nutrients to keep him alive, and he drank water but no food for a year, and he lost about half of his body weight. He went from like 400 ish pounds to like 200 ish pounds, and of course was much healthier. And from that point, was able to start eating food again and hopefully, Started exercising and training his muscles.

And of course he lost some muscle along the way, but not nearly as much as you might think. He wasn’t skeletal, he didn’t look like a, a prisoner of war by the end of it. And so the moral of that story and the key takeaway that you should keep in mind with everything we’ve discussed so far, The more body fat you have, the faster you can lose fat without losing muscle, and therefore then the less body fat you have and the leaner you want to get, the slower you have to lose fat to avoid losing muscle.

And so as a guy, when you are around 10% body fat, or if you are a woman, the equivalent would be about 20% body fat because you weigh less. Your aim should be to lose no more than 0.5 to 1% of your body weight per week. That’s a good rule of thumb for making sure that you don’t sacrifice a bunch of muscle for maximizing fat loss and minimizing muscle loss.

Now, if you have a lot more fat to lose, maybe you’re not 250 plus pounds and 40% body fat, but if you have a lot of fat to. You don’t want to necessarily try to lose it as quickly as possible. So if theoretically, according to the information I’ve shared with you here, you could lose 4, 5, 6 pounds of fat per week.

I wouldn’t recommend doing that. It’s gonna require a huge calorie deficit. Again, can you imagine being in a 3000 calorie deficit every day? Like, go find out how much activity it takes to burn, let’s say. 3,500 or 4,000 calories per day, you’re gonna be very active. And then, so imagine doing that and eating maybe only a thousand calories or 500 calories per day.

That’s not going to be a good time. Even if you could preserve your muscle, you’re gonna have a hard time preserving your will. To go on. And I know losing weight fast is definitely motivating, and especially if you have a lot of weight to lose. I do think it’s smart to be aggressive but not reckless. I would consider a 3000 calorie deficit, a 3000 daily deficit reckless.

So instead do something that’s more sustainable. So, Let’s say you’re a guy over 15% body fat, or you’re a woman over 25% body fat and up to maybe 25% to 35% male slash female, aim to lose about 1% of your body weight. Per week on average, maybe a little bit less, but 1% is a good target. And yes, you can lose more than this without losing muscle.

But if you shoot for 1%, so that might be two, three pounds of fat loss per week, that’s pretty significant. So you’re gonna be very satisfied with that. That is rapid fat loss, and you’re not going to run into the many negative side effects. That come with crash dieting, even if you do it in such a way where you preserve muscle again with like a protein sparing modified fast, which if you wanna learn more about that, I believe I recorded a podcast on it.

So you can probably find it in the feed. And if I haven’t, I definitely have written an article on it. So if you go over to legion and search for protein sparing, you will find.

Okay, so now that you know roughly how much fat you should be aiming to lose every. You can figure out how long you should stay in a calorie deficit for to reach that goal. At least at first, you can find out how long you would need to stay in a calorie deficit for, and that means of course, then you first need to decide how lean you want to get.

What is the goal? And how much body fat are you going to need to lose to get there? So if you are overweight, you have a lot of fat to lose, and you want to significantly improve your health and your aesthetics, then I would say a good first milestone to shoot for is probably 15% if you’re a guy or 25%.

If you’re a woman, that’s when you start to have abs and you start to have muscle definition all over your body. If you’re a guy, you’re gonna notice some vascularity. You’re gonna look athletic, right? And if you want to be even leaner than that, if you’re a guy and you want a six pack, you want clear abs.

Or if you’re a woman, you want very flat stomach and you want lines, maybe about a six pack per se, but you want to look like a lean defined. Toned athlete. Then I would say for the guys, you’re gonna have to get down to probably 10 ish percent body fat and for women, 20 ish, give or take a percent or so.

And if you want to be absolutely peeled as the cool kids say, if you wanna be very lean, then we’re talking about six to eight. Percent for a guy and probably 16 to 18% as a woman. That’s where if you’re a guy, you don’t have much fat to grab anywhere on your body. You’re not gonna be able to pinch much anywhere.

And if you’re a woman, you are going to be able to pinch more than if you’re a guy. And obviously you’re gonna have some fat in your boobs and you’re gonna have some fat in your butt where you want it really. And you’re gonna have some fat in your hips and not so much in your stomach area. Maybe a little bit.

Thighs, but you’re not gonna have much, you’re not gonna have much to pinch. Okay, so now let’s turn this into a concrete example. So let’s say that you are currently 220 pounds and 30% body fat. You’re a guy and you want to get to 15%. That’s the goal. That means you’ll need to lose about 15% body fat, and that’s absolute not relative, right?

So you’re gonna have to cut your body fat in half, and then to figure out how many pounds of fat you’re gonna need to lose. Then we multiply your current body weight 220 pounds by how many percentage points of body fat you need to lose? 15%. Okay? 15% of 220 is 33, so you’re gonna have to lose. 30 to 35 pounds of fat.

Now we know that the goal is to lose about 1% of our body weight per week. And so that’s gonna mean, you know, one and a half, maybe two pounds of fat loss per week. And then what we wanna do is we wanna divide the weight that we need to lose the amount of fat that we need to lose to be specific, that 33 pounds by the amount that we want to lose per week, which is.

Let’s just call it two. So it’s gonna take anywhere from probably 17 to 22 weeks to reach the goal of 15% body fat without losing muscle. And we’re gonna do that by reducing our body weight by about 1% per week, and we’re gonna use a calorie deficit large enough to do that. So that answers the question of how long we will need to stay in a calorie deficit to get there.

But the question I get is, how long should I stay in a calorie deficit for? And so the first part of the answer is what we just covered. You first need to know, well, how long will it take to reach my goal? And then once you know that, you have to determine, how do I. Should I just do that in one go or so in this case, let’s say it’s gonna take 20 weeks.

Let’s just go, go kind of in between the low end and the high end of our estimate. It’s gonna take 20 weeks. So should this person just go for 20 weeks straight, or is that a problem? Well, I wouldn’t recommend 20 weeks straight of dieting because it can be, I wouldn’t say it’s necessarily unhealthy, but it’s going to be unnecessarily difficult because inevitably how it goes when you’re cutting is your first month is usually pretty easy.

If you’re doing it right, you might feel a little bit hungry here and there, and you might deal a little bit with cravings. But again, if you’re doing things right, you’re gonna feel pretty good, you’re gonna sleep well, you’re gonna have good workouts. But then for most people around. Fourth, fifth, maybe sixth week, they start to feel it.

They start to deal with more hunger and more cravings, and now their workouts are noticeably harder. They might even be losing a rep or two here and there on their bigger lifts at least, and they’re certainly not adding weight to the bar or progressing anymore. Whereas many people will continue progressing.

Like if they’re at the end of a lean bulk and they’re progressing and then they start cutting. Many people will still progress for the first couple of weeks while they’re cutting, which is fun, but it doesn’t last. So sometime again, around the fourth, fifth or sixth week, you start to feel that you are in a calorie deficit.

And so that’s why my general advice is to take a diet break every. Eight weeks or so, let’s say six to eight weeks. At that point, when you really are starting to notice it, when you really do want to eat more food and when your workouts are noticeably harder, all the weights are noticeably heavier, and your sleep might be getting.

Impaired and you might be starting to notice more aches and pains in your joints. I know that will happen to me. And if you take a diet break again, you can just plan it in, let’s just say, every eight weeks if you have a lot of fat to lose. So if you’re a guy, let’s say over. 15% body fat, uh, actually let’s say over 20% body fat.

I think it’s reasonable to plan in a diet break every eight weeks or so, and you may get to your planned diet break and feel like you don’t need it at all, especially if you have a lot of fat to lose. And for women, by the way, if you’re wondering, let’s say the, the female equivalent of that would be a woman, over 30% body fat probably doesn’t need to take a diet break more often than every eight weeks.

And so though, if you reach that point and you have. Negative side effects. Really. Again, maybe you’re a little bit hungry here and there. Maybe you feel like, oh, I wish I could eat some more food, but otherwise things are fine. You don’t have to take the diet break. You could keep going and wait until you start to feel some symptoms.

But if you reach that eighth week and you are starting to feel it a little bit, take a diet break, and then as you get leaner, I think it’s smart to take diet breaks slightly more often. So let’s say every six weeks. And so. Numbers to that. Let’s say if you’re a guy around 15% and now you’re cutting to get leaner than that.

Or if you’re a woman around 25% and you’re cutting to get leaner than that, plan on taking a diet break every six weeks, maybe every four weeks. It really depends how your body responds as you get leaner. Now, if you’re a guy who’s lean looking to get really lean, so let’s say you are 10%, you wanna get down to like 7%, or if you’re a woman at 20%, you wanna get down to 16, 17.

Plan on a diet break every four weeks or so, and again, you can play it by ear. I, I like to deload on a very strict schedule. I’ve made the mistake in the past of trying to auto-regulate my deloads and inevitably do with me. I would always push it too far, . I would always push the deload out too long and it would just get in the way of progress.

Sometimes I would end up getting. A cold, and that would become my deload. And I didn’t get the cold because I didn’t deload. But if you are pushing it a bit too far in your training and your body is falling behind in recovery, and the purpose of deloading is to, is to, um, catch up in recovery and to get ready for another block of intense training.

If you are pushing your body too far, it can impair your immune system. You are more likely to get sick. And I can’t say it’s because of regular deloading. There are certainly other factors that would have impacted this. Um, but since I have been deloading on a regular schedule, which has been. Probably a year now.

I don’t think I’ve gotten sick once. I’d have to check my little spreadsheet where I keep records of, of random things like sickness. But I don’t think I’ve gotten sick since I started deloading regularly, and that, that that’s not, that’s not the only reason why, but I’ve definitely noticed that I don’t reach that point.

In my training where I’m like, oh, I definitely should deload now and that, how would, that’s what I would do previously. I would train right up until that point, but by scheduling the deload in, currently I’m following the Beyond Bigger, leaner, stronger 2.0 program, which is gonna come with the second edition of the book, which is going to come out in a few months.

It’s gonna come out probably toward the end of this summer. It has a D load every fourth week. So you do three weeks of hard training de-load. , and I’ve noticed that I’ve been able to train harder than I was training before. I was deloading regularly and not run into any symptoms related to over-training.

So similarly with diet breaks, it’s smart to plan them in every, let’s say four to eight weeks. Just based on the criteria that I’ve shared with you here, and then when the time comes, I think it’s okay to be a little bit loosey-goosey with it. If you feel totally fine, just keep going. If it just seems appealing, if maybe you feel fine, but you’re like, you know, it would be nice just to eat some more calories for a week, then just take the the diet break.

It is not going to slow your progress down any more than. One week, every month or two months. So if you’re gonna be dieting, let’s say for six months, and you’re gonna take a diet break every two months, you have three diet breaks in there. So really all you’re doing is you’re making the whole process take only three weeks longer, but you are going to make it much more enjoyable.

And ultimately more effective because you are going to be able to stick to your diet better when you are taking diet breaks when you need them. Now, how do you do a diet break? That’s what you’re wondering. Very easy. You raise your calories to around maintenance. That’s it. And so what I do is I get an estimate of my total daily energy expenditure.

And if you’re not sure how to do that, head over legion, search for T D E E, and you’ll find an article that has a calculator in it so you can quickly get an estimate of how many calories you’re burning every. and if you want to learn more about everything that goes into that calculator and the theory behind total daily energy expenditure and why it’s useful, you can read the article as well, uh, but you get an estimate of your total daily energy expenditure at that time.

You don’t want to go with what you calculated. At the beginning of your cut or at some point earlier on in your cut, because as your body weight goes down, so does your T D E E. So you wanna get a new estimate of your TDE E before you take the diet break, and then you just eat 90 to 100% of those calories every day.

I like to accomplish that by raising either my carbs only or my protein and my carbs. I don’t raise my fat. I leave my fat where it’s at. I just raise my protein and or carbs, and then you do that for a week. Seven days is a good rule of thumb, and then you get back to your cut. Some people do find that they do better with a bit longer of a diet break, 10 days, even 14 days, but in my experience working with a lot of people, seven days seems to be a sweet spot for most people.

That’s enough to give yourself. A psychological break from cutting and to allow some positive physiological adaptations to kick in that come with not being in a calorie deficit, and then they can get back into the cut, feeling renewed and refreshed basically. And, Then go for another four to eight weeks, depending on their circumstances, rinse and repeat until they are as lean as they want to be, and then come out of the deficit into maybe a maintenance phase or a lean bulking phase or whatever.

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