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On this site, we’ve written multiple articles discussing metabolism, weight loss and dietary restriction techniques, the latter being not only an effective way to lose weight, but also to potentially protect against age-related diseases even in those with normal body weights. But what if you have been working hard to build muscle, and find yourself needing to lose fat mass. Can you do so without losing some muscle mass as well? In this episode of Dr Peter Attia’s The Drive podcast (which focusses on longevity), bodybuilder, powerlifter, and nutritional scientist Layne Norton discusses the subject.

How To Avoid Losing Lean Mass

The good news is that if you are starting with a large percentage of your body mass as fat, then it is easy to lose weight through dieting with very little reduction in lean mass:

I can go from 15% body fat to 7% body fat […] and I lose very little lean body mass. From 7% to 5%, now I’m probably losing 20% to 30% of that weight as lean body mass. [When trying to squeeze off] that last little bit of body fat, you might be losing just as much lean body mass as you are fat mass.

Layne Norton
https://peterattiamd.com/laynenorton/

So the lower the percentage of fat tissue you possess, the more likely you will be to experience loss of lean mass when attempting to lose that fat. Layne Norton likens losing adipose tissue to wringing out a wet towel: it is much harder to wring out that last bit of water than it is to wring out the water when you first start squeezing. His strategy for minimising muscle loss is to use ‘diet breaks’.

I would diet for 2-3 weeks pretty aggressively, try to lose 1.5-2lbs each week, and then I would take one or two or three weeks and eat just at a maintenance level of calories. That worked extremely well for me and extremely well for keeping my strength.

Layne Norton

The level of body fat at which at which loss of lean mass starts to occur might be different for different people. In the show, they discuss ‘body fat set point theory’. This is the idea that there is a relatively tight range of fat mass that the body will try to maintain, and which may vary from person to person. Dropping below this range brings on the negative effects of caloric restriction. Thus, people with a higher set point may experience muscle loss sooner when dieting. Unfortunately, there’s not much data concerning this topic.

Layne Norton also points out that many people may train less while dieting due to a lack of energy, and this may result in the loss of some muscle. He also reminds us that lean mass and muscle mass are not the same thing:

People don’t realise lean body mass is not the same thing as muscle mass. Lean body mass is all non-fat tissues – that’s skin, bone, organ weight, all that stuff, and including your body water. And a lot of, I think, what we see with lean body mass loss is water, gut tissue, liver. Those tissues shrink in response to caloric restriction.

Layne Norton

What About Fasting?

Can you fast without losing muscle? Many of suspected longevity benefits of fasting are thought to be associated with inhibition of cellular growth and division, which would seem an undesirable effect for someone wishing to build muscle.

Peter Attia has anecdotally observed that he doesn’t appear to lose strength during his periods of fasting (which last 5-7 days each quarter), so long as he does resistance training every day during that period. Layne Norton says that it’s much easier to maintain muscle mass than it is to build it. He suggests that while we will probably never have high quality data on the subject, the decision about whether or not to fast might be an ‘optimisation issue’.

Do I think that somebody could build strength, maintain it doing that sort of thing? Absolutely. A lot of that just comes down to being consistent with your resistance training. If somebody says to me ‘I want to be the most muscular, strongest human I possibly can be’, do I think that is still the best thing that they could do? No I do not.

Layne Norton

My take on this is that if the health benefits of resistance training form a large part of your motivation, fasting seems likely to benefit you more than the small amount of muscle you would otherwise have gained by eating normally. However, if you only care about gaining as much muscle as humanly possible and nothing else, you probably don’t want to fast.

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So the take home message appears to be this: so long as you maintain the same level of resistance training while dieting, you should be able to lose most of your fat mass with minimal loss of lean mass, and much of the lean mass you do lose will not be muscle mass. It may be possible to fast and still gain or at least maintain muscle mass, but this is probably not optimal if your only goal is to build muscle.

In the show, Peter Attia and Layne Norton discuss many other topics related to building muscle, including the importance of different amino acids, hormones, and how to stay motivated and consistent. It’s definitely worth a listen: you can find the full show here. Lane Norton also has a training and nutrition-focussed website which you can visit here.