Ep. #370: “Metabolic Damage” and “Starvation Mode,” Debunked by Science

Mike: [00:00:25] Hey, Mike Matthews here from Muscle For Life and Legion Athletics, and welcome to the next and newest episode of the Muscle For Life podcast. This one is about metabolic damage and starvation mode. What science has to say about these things.

[00:00:42] Now, if you are listening to this, there is a good chance that you are either experiencing or have experienced the following scenario. So here you are, you are dieting to lose weight and you’re doing everything right. You know, you’re maintaining a moderate, maybe aggressively moderate calorie deficit. You are eating enough protein. You’re sticking to your meal plan. You are training your muscles regularly and you are limiting your cardio.

And at first everything is going more or less as planned. Your weight and your waist are going down, your waist measurement are going down and your muscle definition is improving. And then the gears inexplicably grind to a halt. For no apparent reason, the scale has stopped moving and your reflection in the mirror has stopped changing.

And you probably, if you’re listening to this and if you are familiar with me in my work, you probably do understand energy balance and so you figure to get the ball rolling again, you should just cut your calories further and maybe increase your cardio. And so you do that. And that works, of course, to a point. And then you get stuck again. And this time you feel even more run-down than before. And so you have a predicament here. What should you do?

Is this just as far as your body will go? Have you reached its set point or its settling point? Is a lower body fat percentage just not in the cards for you? And then you go online and you hear about starvation mode and metabolic damage, and you probably find many stories about people, typically women, who say that they are just not losing weight despite eating very few calories per day and doing hours and hours of exercise per week.

[00:02:41] And the culprit, they say, is supposedly metabolic abnormalities caused by calorie restriction. So essentially, the story usually goes like this dieting, restricting your calories dramatically and incrementally, decreases your basal metabolic rate or your resting metabolic rate. Those are not exactly the same, but they are usually used interchangeably in the story, which then eventually halts fat loss altogether, which then requires a lengthy and rather involved recovery protocol to fix the “damage” should you ever want a healthy metabolism again. Hence the term metabolic damage.

Now, when your body is experiencing the complex set of physiological adaptations that apparently cause metabolic damage, it is said to be in starvation mode, which, according to many people, many so-called experts, apparently kicks in the very first day you begin your diet and just gets progressively worse and worse as time goes on.

[00:03:48] How true is all of this, though? Well, the short story is this: metabolic damage isn’t real, has never stopped anyone from losing weight and doesn’t need to be, “fixed” with complex and meticulous diet voodoo. And starvation mode is sort of real, but isn’t nearly as dramatic as many people think. And in this podcast, you are going to learn why. Furthermore, you are also going to learn the real reasons why weight loss stalls and what you can do to easily break through weight-loss plateaus.

[00:06:23] All right. As always, with these monologue podcasts of mine, let’s start at the top and answer the question: what is metabolic damage? Well, according to most theories, metabolic damage refers to a condition where various physiological systems have been disrupted and as a result, your metabolism burns less energy than it should. In other words, it is a hypothetical state wherein you burn far fewer calories than you should based on your body weight and your activity levels. And I would add to that your body composition as well.

So how your body weight breaks down into muscle, fat, bone, and so forth. Additionally, once you have damaged your metabolism, people say it apparently remains hamstrung even when you have finished dieting and gone back to eating normally and really just want to maintain a steady body weight. Now, it’s called metabolic damage because the theory is your metabolism is quite literally broken to one degree or another and requires fixing.

And in case you’re not familiar with the term, your body’s metabolism is the collection of physical and chemical processes that it uses to produce, maintain, and destroy material substances and to make energy available. So it encompasses a lot of things. It’s what keeps us alive fundamentally.

[00:07:48] Now, the causes of metabolic damage are allegedly remaining in a calorie deficit for too long and or starvation dieting, which is, of course, heavily restricting calories. And also doing too much cardio, that’s also fingered often as well. Therefore, when you stop losing weight for no good reason or struggle to prevent weight gain after a period of dieting, some people will claim that you probably have metabolic damage that needs repairing.

And the evidence to support all this is almost always stories. Stories of people failing to lose weight on a measly few hundred calories per day. And even worse, stories of people gaining weight on very-low-calorie diets and intense exercise routines. And so people everywhere have become convinced that dieting has just screwed up their bodies, maybe even irreversibly, and that their only hope for returning to normalcy is special dietary measures, which usually revolve around some form of “reverse dieting”, where you slowly and carefully increase your calories back up to what should be maintenance.

[00:09:05] And in some cases, they’re also very precise instructions regarding how your macronutrients should break down. So how those caloric increases should break down in terms of protein, carbs, and fat. And the rationale for this approach is that by slowly eating more calories instead of just drastically increasing your intake, which many people do after they’ve been dieting for a while, you are allowing your “injured” metabolism to keep up and process the food efficiently, resulting in a gradual increase in metabolic rate and metabolic health without any unwanted fat gain. Now, as I mentioned, this is generally referred to as reverse dieting. And while I do think it is a good idea to gradually increase your food intake after a prolonged period of calorie restriction, you don’t need to do it for the reasons commonly claimed. And we’ll get into a bit more of that a little bit later in this broadcast.

[00:11:39] So that is a good overview of metabolic damage. Let’s now talk about starvation mode. What is starvation mode? So the idea here is similar to metabolic damage. And it goes like this: if you are too aggressive with your calorie restriction, your metabolism will slow to a crawl, which makes it more or less impossible to continue losing weight without eating less than your average runway model. And according to many “fitness gurus” and “influencers”, if you remain in starvation mode for too long, then the next phase of punishment will begin, which is muscle loss and fat gain.

[00:12:22] Now, the only way to avoid all of this, we are told, is losing weight slowly through a small, you know, 10 to 15 percent calorie deficit. If we get greedy, we will pay for it later. And the way that most people describe it, metabolic damage and starvation mode work together to stymie your progress in a process that looks like this.

First, you eat too little and you lose weight too fast. Second, you plunge your body into starvation mode and then weight loss eventually stops. Third, you eat even less and move even more, which superchargers the response from your body and causes metabolic damage. And then fourth, the longer you remain in the state, the less and less weight you lose, regardless of what you do, and the more and more metabolic damage you accrue that will require more and more time to fix.

[00:13:17] Well, as you are going to learn in this podcast, there is a bit of truth here. There’s a shade of truth. But like many things that everybody knows in the fitness space, it is more wrong than right.

[00:13:29] So let’s start in that direction with this: weight loss does not damage your metabolism. That’s it. Drop the mic.

[00:13:39] Okay, pick them back up. All right. So let’s break that down. To understand the real science of fat loss, you have to start with the principles of energy balance, which you are probably familiar with. That is how your energy intake and your energy expenditure alone dictate weight gain, weight loss. Once you understand that, you realize that meaningful weight loss requires that you eat fewer calories, less energy than you burn for an extended period of time. For most people, the learning stops there.

They wanted the one weird trick that would melt away belly fat and love handles and they got it. Eat less and move more. What they don’t know, however, can come back to haunt them because restricting your calories does more than just reduce your total fat mess. It also affects your metabolism in various ways that make getting leaner, increasingly difficult as time goes on. In short, when you restrict your calories to lose fat, your body sets out to decrease your energy expenditure and increase your energy intake. In other words, it wants to erase the energy deficit, to balance the intake with the output and thereby halt fat loss.

[00:14:54] You see, the reality is losing fat requires that you force your body to do something it doesn’t want to do. It really is mild and prolonged starvation. And in the spirit of self-preservation, your body has defense mechanisms to employ to fight back. And I think it’d be helpful if we covered the major ones.

[00:15:15] So first, your basal metabolic rate will slow down. Basal means forming a base. It means fundamental. So your basal metabolic rate is the amount of energy that your body burns while at rest. The biggest energy hogs in your body are your organs and your muscles and those are the prime determinants of your basal metabolic rate. They burn a lot of energy. They require a lot of energy to keep working.

[00:15:40] Now, when you place your body in a calorie deficit, hormonal adaptations occur that cause your body to burn less energy while at rest. The major ones, the major hormones involved in these adaptations include leptin, ghrelin, thyroid hormones, and testosterone, which are all unfavorably impacted by calorie restriction and weight loss.

[00:16:03] Another defense mechanism relates to the thermic effect of food. The thermic effect of food decreases and the thermic effect of food, or TEF, as it’s often referred to, is the amount of energy that is required to eat, digest, absorb and store food. Now, research shows that TEF accounts for about 10 percent of total daily energy expenditure and most people with amounts varying based on the macronutrient composition of the diet. TEF is higher with protein and carbohydrates than fat, for example. Now, while restricting calories doesn’t appear to directly reduce TEF, the reduction in overall food intake naturally results in a reduction of TEF.

[00:16:52] Another defense mechanism that your body has is when you are in a calorie deficit, you tend to burn less energy through spontaneous physical activity. So every day you engage in varying amounts of spontaneous activity, like walking around while you’re on the phone, hopping to the bathroom, drumming your fingers when you read, bobbing your legs and you think, and so forth. And the energy burned by these activities is known as non-exercise activity thermogenesis or NEAT.

And NEAT plays a much larger role in total daily energy expenditure than most people realize. In fact, research shows that NEAT can vary by up to 2,000 calories per day among people. And the same research indicates that people could burn an additional 350 calories per day by just doing simple things to increase their general activity levels, like taking the stairs when possible, walking relatively short distances instead of driving, doing chores instead of watching TV, and so forth.

And when you’re in a calorie deficit, your body naturally decreases its spontaneous activity levels. And this happens subconsciously, We’re not even aware of it. We just naturally tend to move less and this often significantly reduces our total daily energy expenditure, Our average daily energy expenditure. Furthermore, studies show that this NEAT adaptation can remain for quite some time after regular eating has resumed. Which, by the way, is one of the reasons why weight gain after dieting is so common.

[00:18:39] Okay, one last defense mechanism is: burning less energy during exercise. As you reduce your body weight, you also reduce the amount of energy that you expend during exercise because it costs more energy to move a heavier body. That said, there does appear to be a bit more to this because research has shown that even when body weight is artificially increased during weight loss, energy expenditure during exercise remains lower than normal. And the scientists that conducted that research I’m referring to are not exactly sure why, but it has been observed.

[00:19:16] So when we put this all together, what we see is that our total daily energy expenditure really is a moving target. And one of the challenges of dieting is adapting our exercise routines and our meal plans as needed to ensure that we remain in a large enough energy deficit to keep losing weight and keep losing fat.

[00:19:37] So all of these changes that we just discussed to our basal metabolic rate, NEAT, TEF, and so forth are collectively known as adaptive thermogenesis and they constitute our bodies primary weight loss countermeasures, you could say. And these things can be very effective as well. If you do not know how to deal with them properly, they can significantly slow your rate of weight loss or even stop it altogether.

[00:20:09] What they can’t do, however, is break your metabolism even when you heavily restrict your calories, eat too little protein and do little or no strength training. You can expect a larger reduction in your basal metabolic rate if you do those things, but the effects are far smaller than many people would have you believe.

[00:20:32] Several studies have shown that the metabolic decline associated with dieting, including long periods of very low-calorie dieting, ranges from less than 5. Percent to about 15 percent. Furthermore, it took about a 10 percent reduction in body weight to produce the larger double-digit drops. And most of the research on the matter was conducted with people who made every mistake in the book.

They eat far too few calories and far too little protein and did no resistance training whatsoever. We also know that while these effects can persist long after weight loss has stopped, they can also be easily reversed by just raising your calories, lifting weights, or doing some form of resistance training at least, and eating a high protein diet. That’s all it really takes.

[00:21:24] Now, what happens to your body when you do things correctly? When you use a moderately aggressive but not reckless calorie deficit, when you eat somewhere around one gram of protein per pound of body weight per day, and you do a few hours of heavy resistance training every week and don’t overdo with the cardio? Well, studies show that that approach to fat loss can actually increase your metabolic rate and your total muscle mass.

So really what we are talking about is this: metabolic damage is a misnomer. The more accurate term is metabolic adaptation, which can work for or against you depending on your goals, actions, and circumstances.

[00:22:08] Okay, so now let’s shift gears and talk starvation mode, because starvation mode is not real. Not in the strict sense of how most people understand the term, at least. So as you now know, your body does respond to calorie restriction with crosscurrents that are meant to stall weight loss. Right? Adaptive thermogenesis. But there is no “mode” that it enters or physiological switch that flips that makes any further weight loss impossible.

[00:22:40] And the best example of this and really of everything that we are going over in his podcast that I know of is one of the most extreme studies on human metabolism that was ever conducted: the Minnesota starvation experiment. So this experiment started in 1944 as the end of World War II was approaching and its purpose was to discover the healthiest way to help the millions of starving people in Europe return to a normal body weight.

As you can guess, this study involved starving people. And by starving, I truly mean starving. So what scientists did is they took 36 volunteers – now, these were guys who had the choice of shipping off to the front lines or doing this and they chose this – and to replicate the conditions of your average POW camp, the researchers had these men do several hours of manual labor every day and march about 22 miles per week.

And they put them on a diet that provided about 50 percent of their average daily energy expenditure. And they did all that for six months. So, as you can imagine, things got pretty grim. By the end of the study, many of the men looked downright skeletal and some had almost starved to death and one dude even cut off several of his fingers to wash out early.

[00:24:03] What about their metabolisms, though? Were they as devastated as proponents of metabolic damage and starvation mode would predict? Absolutely not. After losing about 25 percent of their body weight, on average, their Basal metabolic rates were on average about 20 percent lower than scientists predicted based on their body weights. In other words, their metabolisms were underperforming by about 20 percent on average. After enduring six months of the most extreme weight loss regimen you could ever devise.

[00:24:38] Then in the next phase of the study, subjects were put on a recovery diet to allow them to regain most of the weight they had lost. And after 12 weeks of this, their metabolic rates were assessed again. This time, the average metabolic rates were only about 10 percent lower than where they should have been. And in some cases, everything was back to normal, as if nothing had ever happened. Just 12 weeks of normal eating.

[00:25:03] Now, that’s not great news. Of course, when you take it on the whole, you still had some lingering effects, but not too bad considering what these guys had put their bodies through.

[00:25:13] For example, if you started your weight loss journey with a basal metabolic rate of about 1,800 calories per day and then you went and played concentration camp for six months and then regained the weight loss, you could expect a basal metabolic rate of about 1,600 calories per day. Again, not ideal, but not enough to make you incapable of losing more weight.

[00:25:39] It’s also worth noting that according to a recent study that was largely compiled by a member of my scientific advisory board, Menno Henselmans, when you look at the data over the long term and not just the first 12 weeks of recovery dieting, there’s no evidence any of the people in the experiment suffered from lingering metabolic damage. In other words, everything went back to normal. But in some people, it just took longer than 12 weeks.

[00:26:09] Now, this groundbreaking experiment provided another nail to drive into the coffin of starvation mode, and that is: every participant continued to lose weight up until the very end. The rate of weight loss slowed down, of course, for reasons we’ve already gone over, but it never came to a complete stand still. So it is safe to assume then that if people can eat about 1,500 calories per day and do many hours of moderately intense exercise every week and still lose weight steadily for six months, then we have nothing to worry about.

[00:26:50] So if metabolic damage and starvation mode cannot cause you to stop losing weight, what can? What are the real reasons you stop losing weight? Well, there are three main reasons why you stop losing weight. And they are one, you are retaining water, two, you are gaining muscle, and three, you are eating too much, and most often eating more than you think. That’s it. Your metabolism is not a unique snowflake. Your body runs on the same type of machinery as mine and everyone else’s. You just have to learn how yours is tuned and you got to make sure that you are not making some of the major weight loss mistakes that keep people fat and frustrated.

[00:27:38] And if you want to learn more about that, you can head over to Muscle For Life and search for an article called “The Definitive Guide to Why You Are Not Losing Weight“. And I’m not sure if I recorded a podcast on it or not. So I may have also recorded a podcast on it.

[00:27:54] All right. So let’s wrap up here, let’s summarize. Metabolic damage and starvation mode are mostly boogeyman. Your metabolism might decline as you lose weight, but it might not, depending on where you’re at, what you’re doing. But if you do things right, if you don’t heavily restrict your calories, eat enough protein, if you train your muscles, and don’t fry yourself with cardio, the metabolic effects of the diet will be negligible and will be quickly reversed with either a short period of reverse dieting where you just jump your calories up to maintenance in a couple of steps or just going right back to maintenance or somewhere right around where your maintenance should be once you have reached your target body fat percentage or your target body composition. 

[00:28:44] And even if you have already done everything wrong to draw pounds, even if you have already starved yourself and eaten very little protein and done way too much cardio, you still do not have anything to worry about. Your metabolism is okay because even the most extreme dietary measures can only produce a relatively small decline in metabolic rate, which just disappears naturally with normal eating.

[00:29:14] And lastly, if you are currently stuck in a weight-loss rut or have been in the past and want to know why and how to prevent it in the future, it almost always comes down to one or more of three things: water retention, muscle gain, overeating. And again, if you want to know why, head over to Muscle For Life and search for “not losing weight” and you will find an article I wrote called “The Definitive Guide to Why You Are Not Losing Weight”. And I may or may not have recorded a podcast on that as well. So you can search that in the podcast feed.