00:49 Anabolic resistance
01:23 Mitochondrial dysfunction
02:31 Impaired recovery capacity
03:56 Lower testosterone and GH levels
05:15 The hard data
06:06 New Ribeiro et al. study
08:10 Practical application
What is the optimal body fat percentage range for muscle growth? In other words, when should you stop bulking? For some people, this is of course, a matter of preference. Some people don’t like to lose visual contact with Johnson and the twins. Some people don’t like not being able to squeeze into their favorite jeans. But from a scientific perspective, this is not purely a matter of personal preference. There are also physiological reasons to be aware of. In this video, I will discuss what the science says about what the optimal body fat percentage ranges to put on muscle and strength. Being overweight has a number of negative metabolic consequences.
Some of those may be directly relevant for strength trainees trying to put on muscle and strength. One in particular is anabolic resistance. Research has found that overweight individuals They have a lower protein synthetic response in response to meals and strength training. The research on this is not crystal clear, but the general trend is decidedly negative. Finding that myofibrillar protein synthesis in response to strength training workouts and protein feeding is lower in obese and overweight individuals versus leaner individuals. Since muscle growth is in large part the result of the accumulation of muscle proteins. This could, of course, harm muscle growth.
Second. Being overweight is associated with mitochondrial dysfunction and insulin resistance, which may impair the muscles ability to generate energy for exercise, which could in turn compromise exercise performance, which could in turn impair your gains. Third. Being overweight in particular, if you have high insulin resistance, which is strongly correlated with body fat percentage, that often also entails high chronic inflammation. Higher body fat levels cause higher insulin resistance levels and higher insulin resistance levels are strongly associated with higher chronic inflammation levels.
We have research showing that high chronic inflammation levels can impair muscle growth. Inflammation and muscle growth seem to work together in a signal to noise kind of fashion whereby you want acute spikes of inflammation, but you want low chronic levels of inflammation to make the immune system pay attention to your muscles after a workout. It will respond to acute inflammation, whereas if there is high chronic inflammation, the signal is kind of drowned out in the noise of the chronic inflammation. However, most of this research is limited to elderly individuals. Forth. Being overweight can harm your recovery capacity. Multiple studies have found that overweight individuals typically take longer to recover from a given workout than leaner individuals. There is also such a thing as too lean whereby if you get to really low body fat levels like contest prep levels or anorexia, that also compromises your recovery capacity. So there seems to be a sweet spot at some level of healthy body fat where you also recover the easiest from your workouts, your recovery capacity influence how much volume you can do, and that in turn influences how much muscle and strength you can build. So impaired recovery capacity can logically also impair your ability to build muscle and strength. There’s also a cardio respiratory factor whereby being heavier in general both for muscle and fat, but in particular from fat can decrease work capacity and decrease how fast you recover in between your sets.
I notice even a few kilograms difference in weight myself when I’m kickboxing is already a serious effect on how easy it is to maintain your stamina. The more weight you’re dragging around, the harder it is to supply oxygen to all of those tissues and get blood there and provide nutrients there and therefore keep going. I’ve seen myself that improving your cardiorespiratory fitness can have a significant effect on how quickly you recover in between your sets of strength training, which can in turn also indirectly benefit your ability to build muscle and strength. If you’re completely gassed out after every set of biceps curls of course your workouts are going to take a long-ass time.
Five. High body fat levels have a decidedly negative effect on your anabolic hormone levels, especially in men. In men, the higher your body fat level, the more of the testosterone you produce. Is aromatized to estrogen. So the ratio of your testosterone to estrogen, which would normally be favorable – a masculine ratio, is a lot of testosterone, not so much estrogen. This decreases the higher your body fat level goes. And you can even get to the point where you develop something that’s called male obesity-related secondary hypogonadism, which is basically that your testosterone levels become clinically low as a result of being overweight. So higher your body fat level, the less testosterone you have, the more estrogen you have. And that can also cause symptoms like gyno, which is basically breast formation.
And of course, this might be negative for long term muscular development. In women, the effects are not nearly as bad. But there is research showing that growth hormone levels potentially at high body fat levels and certainly also estrogen levels, when you get to very high body fat levels can become impaired Testosterone levels typically don’t go down maybe until you get to extreme levels. But women don’t have as much to fear from this because in general, women have superior metabolic health. They don’t suffer as much as men do from higher body fat levels, metabolically speaking at least. Now, theory and mechanistic data are nice, but what do the hard data say? Do we have nice research with long term studies on muscle growth, dividing people into multiple groups of higher and lower body fat levels and then really testing do they actually built different amounts of muscle? Relatively recently I debated this with Mike Israetel, Greg Nuckols and Eric Drexler on Jeff Nippard’s YouTube channel.
I’ll spare you the details because it’s a two hour debate and we didn’t have a lot of high quality data to go by, some rat research, associative data, meta analysis with multiple confounders and a lot of data on untrained versus untrained individuals rather than strength trained individuals. basically my stance was that since the empirical data are inconclusive and we have significant mechanistic data indicating that there might be negative effects of higher body fat levels, I think muscle growth is probably going to be negatively affected. It turns out I was wrong. After the debate, a new study came out dividing people into low, medium and high body fat levels, put them on a strength training program for six months and looked at who was gaining the most muscle. It turns out there was no difference in muscle growth between the different groups of different body fat levels. This new research caused me to completely redo the literature search for my PT certification program. In our PT course, we have pretty much all the research, at least that we can find on pretty much every topic, whether it’s exercise, or the rest intervals, anything that can influence your ability to build muscle strength for fat loss. We have done a complete literature search with all of the research we have, or so we thought, because it turns out that – locked away in the deepest depths of he… Google Scholar. There were actually some other studies that somehow nobody had found before and were also not discussed in the debate. And those studies quite conclusively show your body fat percentage or your body fat level in general has no effect on your ability to build muscle mass. Interestingly, they do seem to have a negative effect on strength development.
Now, whether that’s also a concern for relatively healthy, overweight strength trainees with good muscle quality, maybe not, but it is something to be aware of. That strength development might be compromised by high body fat levels, whereas muscle growth almost certainly won’t be even up to relatively high levels in older individuals. And this, I think, is also a very good lesson that very often it’s very tempting for humans to go by stories. We like to create stories in our minds of why A causes B and why therefore C is the result. And I think people in general and also many scientists, especially scientists that are educated in the natural sciences, they tend to overvalue mechanisms and theory and logic over hard empirical data. You can see this with people like Andrew Huberman, for example, which I think is overall great, but at times extrapolates very heavily from mechanistic data and turns that into practical applications that go far beyond what the actual data really show. Now let’s talk practical application. What does this mean for when you should really and the bulk?
Well, it turns out that muscle growth is probably not going to be affected and you can keep bulking in that sense for as long as you want. It’s just a matter of personal preference. At some point, strength development might become a factor, but this is quite questionable based on the current research. However, practically speaking, I really don’t see any reason why especially men should bulk up to a point where they lose their abs because of all these negative metabolic effects, even if they don’t directly impeach your ability to build muscle. It’s certainly not going to be good for your health. And I think that in practice, for serious strength trainees, the impaired recovery capacity we see in overweight individuals as well as the lower work capacity is probably more relevant than we currently have data of in studies. So while there is no direct effect on your body fat level, on your ability to build muscle, I think that if your work capacity and your recovery capacity are going to be significantly compromised by your high body fat level, that might impair your MRV, your maximum recoverable volume and thereby impair your ability to accumulate volume and build muscle and strength.
Plus, there are some practical considerations. First of all, esthetics. Why would you bulk up to a higher body for levels if you can stay in a lower range and some issues with skin elasticity and stretch marks, which are a lot more likely to become problematic at higher body fat levels, and especially if there’s a huge difference in the amount of weight that you get. So in practice, I really don’t see why you would bulk up to a point where you lose your abs as a guy. But there’s probably also no direct hard negative effect on your ability to build muscle and strength. For women, most of this is really a mood issue because in my experience as a coach, at least women will almost never want to bulk up to a level where they actually start suffering from the negative metabolic consequences of being overweight now. I still don’t recommend going up to overweight body fat levels. But even at that point, muscle growth probably isn’t going to be impaired. So for women, it really is mostly a matter of personal preference. And if anything, for specifically for fit women in the fitness industry, it’s more likely that they want to go to excessively low levels, in my experience, then excessively high levels. So be aware of that. If you are a woman, it’s certainly not the case that lower is better.
So I think that sums up everything you need to know about the optimal body fat level for maximum gains. I hope this knowledge helps you and if you like this type of evidence based fitness content, I’d be honored if you like and subscribe. By the way, since you seem to be into evidence based fitness content, you might be interested in the online Henselmans PT certification course. You’ll learn absolutely everything you need to know to get results like these. The link is in the description.
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