Fat Loss

Lose Body Fat Without Losing Muscle, Slowing Your Metabolism

by Mike Mutzel


The health benefits of ‘weight loss’ are cancelled out if the weight that you’re losing is from muscle. Here's why you should prioritize protein and resistance training to lose body fat instead.



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Studies Mentioned:

Christoffersen, B. Ø. et al. Beyond appetite regulation: Targeting energy expenditure, fat oxidation, and lean mass preservation for sustainable weight loss. Obesity 30, 841–857 (2022).

Time Stamps:

0:20 Weight Regain due to muscle loss

0:45 Prioritize muscle health with fat loss

1:47 Stimulants have side-effects

2:24 GLP-1 agonists aren’t great

3:23 Metabolic Adaptations with dieting

4:00 Brown fat activation

4:55 Lean tissue loss

6:10 Aerobic VS Resistance Training

6:23 Preventing muscle loss

7:27 This image explains all

8:15 Preventing fat gain

9:50 Brown fat activation

11:59 Consistency is key with brown fat activation

12:45 Cold plunges and heart health

Podcast Captions:

When it comes to losing body fat and keeping the weight off, it's important to recognize that you should focus on strategies that help preserve lean muscle mass, as well as activating brown adipose tissue. We're going to draw upon an excellent review article that highlights the importance of this because what generally happens when people go through these weight loss cycles and dieting cycles is they regain much of the weight that they lost, yet their resting metabolic rate after they lose the weight and regain it, is actually lower than when they started. When people are doing this for years on end, their resting metabolic rate is quite stagnant because they've slowed down their energy expenditure, their volitional movement, and they've lost skeletal muscle and the size of their metabolically active organs actually shrinks.

It's important to recognize that going forward for you or people in general when you're focusing on dietary strategies to lose body fat, that you prioritize the maintenance of and preservation of lean skeletal muscle whilst also activating your brown adipose tissue. This is a great figure here from an excellent review article, figure five, talking about the importance of preserving muscle growth and activating the brown adipose tissue.

They have other different strategies here like SNS activation, activating the central nervous system. I'm not a huge fan of those strategies. Clenbuterol has been around for a long time. A lot of bodybuilders use this. You feel terrible. It actually increases your appetite over time. It's not a good, in my opinion, not a good way to go about. Activating your brown adipose tissue and browning your fat and preserving muscle mass is, so the scientists say we should rethink approaches for weight maintenance by targeting energy expenditure and lean mass preservation.

The potential ways of maintaining or increasing energy expenditure include a diversity of targets ranging from sympathetic nervous system activation, clenbuterol and other drugs that, again, I don't generally recommend because they do have side effects and consequences. We should also focus on non-shivering thermogenesis in a myriad of different organs. One of the best ways to do that is deliberate cold exposure.

The title of the paper that we're going to talk about today is Beyond Appetite Regulation, Targeting Energy Expenditure, Fat Oxidation and Lean Mass Preservation for Sustainable Weight Loss. Why do I highlight or emphasize sustainable? Because some people lose weight for a wedding or an upcoming event and they regain all of the weight that they lost, and then their metabolic rate is suppressed for years upon end. We've talked about this data for a very long period of time.

Now, it's important to acknowledge that there's a lot of new drugs that are out there that people are taking such as semaglutide and the GLP-1 agonist, and research has been shown that after 52 weeks of continuous use of these medications, at best, you're going to lose seven pounds of fat, only 0.4 pounds of visceral fat, which is a nothing burger, by the way. If you want to pay me $300 a month, I will help you lose way more than seven pounds of fat. I say $300 a month because that's what the cost of these drugs are on the low end. On the high end, it can be $1,200 a month. Imagine paying 6,000 a year or something or more for a drug that only causes seven pounds of weight loss.

Here's the rub. These drugs actually cause about four to five pounds of lean muscle mass loss. The weight loss is not going to be sustainable because they are preferentially targeting for whatever reason mechanistically, the loss of muscle mass, and they're not inducing the brown adipose issue or preserving skeletal muscle. The scientists say weight regain is almost inevitable, and it often leaves patients in a worse position because of the metabolic adaptations and a less favorable body composition caused by loss of lean mass and a regain primarily of fat mass.

You can see how years of yo-yo dieting can lead you to be skinnier and skinnier, have less and less lean mass, yet more and more fat. Your body composition shifts. This is why many people focus on DEXA scans while we focus on looking at whole body MRIs and other strategies as opposed to just looking at the scale, because you don't know where the fat is coming from.

Now, as I mentioned, brown adipose tissue activation is a huge target. A lot of people are doing this now. That's why I'm such a big fan of deliberate cold exposure. This show is brought to you by our friends over at icebarrel.com, the only American made 110 gallon cold plunge tank that makes getting into a consistent cold practice easier than ever. The great thing about the ice barrel is you do not need a chiller. They make an ice block mold kit that makes seven pounds of ice that lasts much longer than traditional cubes. You just fill up the durable silicon ice block molds with water, put it into your ice barrel, and then when you're done, you put it back in the mold, put it back in your freezer, which makes deliberate cold exposure and being consistent with this practice, much easier to do so.

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Let's go back to figure two of this article and talk about why it's so important to focus on preserving lean muscle tissue while losing weight. Because it turns out that about 30% of the weight that's lost when you diet and you do excessive amounts of cardio comes from muscle tissue, but not just muscle. From your heart, your liver, your kidneys and pancreas, actually they decrease in size, which impacts your resting metabolic rate. This is really important to recognize. Prior to reading this article, I didn't realize that the size of your heart, liver, and other metabolically active tissues like the pancreas and kidney can actually decrease in their size, and that might lead to the long duration suppression of resting metabolic rate when people start yo-yo dieting and doing extreme calorie deprivation and over exercise.

It's important to recognize that the currently available strategies for weight loss can deliver substantial decreases in fat mass. However, 15 to 40% of the weight loss represents reductions in skeletal muscle and the size of these organs. The scientists say, besides reducing skeletal muscle, weight loss also decreases the mass of highly thermogenic organs such as the liver, heart, and kidney. The decreases in resting energy expenditure because of the decreases in lean mass can be substantial. It's important to focus on resistance training.

We're going to talk about brown adipose issue in much more detail very, very soon. This is why when you're going on a diet, you want to look good for a wedding, you have some sort of event coming up, you want to be tight in your clothes and all that, you've got to focus on weight training because as it turns out, when you're doing resistance training, you help to preserve lean muscle mass even if you're in a calorie deficit. I really want to focus on this because you see people at the gym, they're doing cardio, they're running all the time, they're on the exercise bike, they're burning all these calories, but they're not doing resistance training. We really need to focus on preserving lean muscle mass, not just losing fat or overall weight.

The scientists say, furthermore, after weight loss, most of the weight regained is typically fat mass leading to a progressive decline in lean mass loss over several weight cycles, thereby further exacerbating the reduction in energy expenditure. Hence drug candidates and other modalities that either spare the loss of lean muscle mass or even increase lean mastering weight loss could potentially prevent part of the reduction in energy expenditure and thereby enable a more pronounced and sustainable weight loss. This is why I'm not a fan of semaglutide and Ozempic and all these drugs that are marketed as cure-alls because it's not causing people to change their habits or their lifestyle. They're taking this drug, they're probably eating the same foods, they're not resistant training. We should really focus more on resistance training and possibly brown adipose tissue activation and intermittent fasting. All these strategies that can help preserve lean muscle mass.

Here's a great figure that helps to encapsulate everything that we're talking about. You can see figure one, traditional calorie restriction. People want to go on a diet, they want to lose some body fat for an upcoming event, they're starving themselves eating carrots and celery sticks and not enough protein. What happens? Well, you see the appetite increases, desire to eat increases, and you see a marked reduction in energy expenditure because most of the weight that is lost is coming from lean tissue because protein is not being optimized and there's not a focus on resistance training.

However, in part C of this figure, what do you see here? You see energy expenditure is maintained, and as you can look here over the weight loss maintenance phase, you see an overweight person on the figure A, and then in part C, you see a lean person. There's better preservation of weight maintenance. The scientists say weight regain is almost inevitable, and it often leads the patients in a worse position because of the metabolic adaptations and a less favorable body composition caused by weight loss of lean mass and regain primarily of fat mass. We want to prevent that. We're going to focus on brown adipose tissue very soon, but this is why enhancing the energy expenditure and preservation of lean mass by way of resistance training is so important and so vital.

Again, just focusing on cutting calories and burning calories at the gym, we want to focus on resistance training, priming those muscles, improving the anabolic response in the body, optimizing protein. We've talked ad nauseum about the importance of that. This figure does a good job about focusing on the long-term weight loss maintenance, not just short-term weight loss. Because again, what you see here is energy expenditure is suppressed in figure A, and that's where most people, what they ultimately do. You can see here the different metabolic adaptations that occur, you get an increase in ghrelin, which causes an increase in appetite. You get a decrease in GLP-1 and PYY and CCK, and all the different peptides, changes in thyroid hormone, basal metabolic rate, and the thermic effect of food. All of these things are going down along with lean mass. That's what you want to avoid.

In contrast, if you do a mild calorie restriction, intermittent fasting, alternate day fasting, some sort of protocol like that, and you focus on protein and you optimize for resistance training, preserving lean mass, you can expect more sustained weight management and that preventing the offset of muscle mass and lean mass.

Let's talk about the importance now, because as you saw in figure five, brown adipose tissue activation is really important for optimizing your overall metabolic rate and energy expenditure and ability of your metabolism to oxidize fat. It's been known since 2004 from this study from the New England Journal of Medicine that cold activated brown adipose tissue in healthy men is achievable, but it turns out there's this inverse relationship with the prevalence of obesity and insulin resistance correlating with a dearth or a decreased activation of cold induced brown adipose tissue thermogenesis.

The scientists say brown adipose tissue activity was observed in 23 of 24 subjects, so in about 96% of subjects, there is some activity in this metabolically important brown adipose issue. However, the activity was significantly lower in overweight or obese subjects than in the lean subjects. The BMI and percentage of body fat both had a significant and negative correlation with brown adipose tissue, whereas resting metabolic rate had a significant positive association. It turns out that your brown adipose tissue is intimately involved with your overall metabolism and ability to oxidize fat for fuel. This is why I'm such a big fan of getting cold on purpose. We've talked at length about different ways to do that, starting with a cold shower, going out when it's cold outside with minimal clothing, going in cold oceans, lakes, rivers, streams, or investing in something like the ice barrel tank because that makes it so easy to use. It's on your back porch. There's really no excuse. I did three minutes this morning. I was a little bit cold, a little bit shivering, but afterwards, the shiver response, it gets better over time.

You have the non-shivering thermogenesis, that actually increases your metabolism by increasing all of the hypermetabolic responses, the adrenaline, the noradrenaline. This is acute, this is transitory. It's not going to make you excessively stressed. It's important to acknowledge that your brown adipose tissue is really important for your overall health as well. It turns out that it's a key target for maintenance and preservation of a healthy body composition. The more fat that you have, there's a greater onus or impetus to actually get cold on purpose and deliberately activate these brown adipocytes and cause your white fat cells to behave more like brown fat. That's called adipose tissue beiging. We've talked about that with Ben Bickman and other experts over the years. Consistency matters more than length.

This was a recently published paper titled Repeated Short Excursions from Thermo Neutrality is Suffice to Restructure Brown Adipose Tissue. Now, just a disclaimer, this was in animals, but it's important to recognize what the scientists observed. We see this anecdotally with people who habitually cold plunge, they're more tolerant to cold environments and probably have an higher activity of their brown adipose tissue and thereby metabolic changes that are favorable. The scientists say, “We observed here that even a very short daily exposure to moderate cold suffices to bring about alterations in brown adipose tissue structure observed as an increase in protein density at an increase in the cytoplasmic density in the micrographs of the brown adipose tissue, increasing the mitochondrial density and the uncoupling protein response that is characterized by people who do this deliberately.” This was a study in the Ama pearl divers, a really fascinating observation.

You can Google, I think National Geographic did a big future story on these Japanese women. I think it's a great way to sort of look at what are people doing in the real world and how is it benefiting them? As you can see here, the arterial stiffness in the coronary arteries and the carotid arteries are actually much lower in the pearl divers compared to other people in neighboring communities that are not doing this occupation. The title of this paper is Arterial Stiffness of Lifelong Japanese Female Pearl Divers. Again, this is a tradition that's been going on for over 2000 years in Japan, and I think it's really cool that scientists are now quantifying the physiologic changes that are experienced or imparted upon these women that get cold on purpose.

As I mentioned, historically, these women would do this naked. They would do this year round. They are free diving, so they are exercising at the same time, but you can't argue the fact that they are in super cold water all throughout the year. Their activity of the brown adipose tissue and this cold induced vasodilation response that we've talked about, and that is that as your body gets more acclimated to getting cold on purpose, there's an anticipatory and an early vasodilatory response to help to preserve skin temperature. That is also associated with a reduction of the shivering response, but an increase in the non-shivering thermogenesis. Once you start getting cold on purpose, you might shiver a lot. Your muscles are going to start to shiver, but as you get more adapted, the non-shivering thermogenesis response will actually increase, and that is characterized by increased acclimation to the cold. If you don't like to get cold now because you take a cold shower and you're shivering for 30 minutes, trust me, that will get better over time. It's been shown that the muscle induced shivering thermogenesis response actually decreases as there's an increase proportionally in the non-shivering thermogenesis, which could be important for helping to activate the brown adipose tissue.

One more study here from 2019 I think it's important to acknowledge. The Browning of White Fat Agents and Implications for Beiging of Adipose Tissue to Type II Diabetes. It's important to acknowledge that scientists say, while some metabolic disorders in obesity are commonly linked to type II Diabetes, brown adipose tissue contributes directly to the disease onset and permanence.

We know that about 96% of American adults have some degree of metabolic dysfunction, and so we should be focusing on priming our brown fat, getting cold on purpose. This is just another thing that is part of healthy living. Three, 400 years ago, you didn't have all these thermo neutral environments in your workplace, in your car. You had to go out and hunt and forage and gather food and work out in the cold, and we're just not doing that anymore. This is why deliberate cold exposure therapy is such a hot topic now because people recognize the importance of this, how good they feel.

There was one study where just five minutes of getting cold on purpose actually changed all these different neural networks, improving feelings of positivity and mental affect. There's multiple pleiotropic interconnected mechanisms here that are very important, but we know that the loss of brown fat is part and parcel with the change in body composition and metabolic health.

In summary, don't just focus on losing weight, focus on preserving muscle while losing fat and activating your brown adipose tissue. I think that this should become a lifestyle. This should become an important kitchen table topic, not just focusing on dieting and calorie restriction, because we know that over time, much about 40% of the weight that is lost via those strategies actually is regained in the form of fat. You get this mismatch where you're at the same body weight that you were before you started over time, and yet you have less lean mass and you have a slower resting metabolic rate, decreased energy expenditure, and this is just a bad place to be in a healthy maintenance phase. We've got to focus on preserving lean mass, prioritizing protein between 1.2, 1.6 grams per ideal lean body mass, hit the weights. We've done many videos about resistance training, how to periodize, where to start. I will link some of those in the description below, my friends.

I'm grateful that you tuned all the way in. Thanks for hitting that like button. Let me know what you think in the comments and we'll catch you on a future one down the road.


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