Can muscle turn into fat?

Today this citation came up on Mehdi’s site

Muscle loss? Forget about it. Fat gains are possible, but not because of that broscience nonsense of “muscles turn into fat” – muscle can’t turn into fat any more than mud can turn into gold because they’re 2 different tissues. In reality, if you gain fat, it’s simply because you ate more (junk food, mojito’s) and burned less (no training, lying at the beach all day) ==> caloric excess == fat gains.

and I felt this merits a response.

Before I go further – I love Mehdi. He is a great guy, and his Stronglifts book – when you could still get it on his site – was a gem. A bit of a rough gem, but a gem nevertheless – and it got me into heavy lifting, which is probably the most important change in my training that I have made.

I dont always agree with his take on science though, and the above citation is one that I would respectfully disagree. Muscle can turn into fat under the right circumstances. The metabolic pathway is certainly there: muscle is broken down into amino-acids (not different from your steak, really), which can be converted into glucose by the liver, and which can further be converted into fat and stored.

The question is, does it actually happen in practice. Chances are, not too often, as obviously muscles are generally broken down in periods of caloric deficit, in which case the glucose is probably not converted into fat but rather burned and/or stored as glycogen.

However, consider an athlete who is really big (and also has low levels fat), maybe because he just trained hard, or because the juice has also helped a bit. If for some reason his body decides that muscle is too costly to carry (eg becausehe is lying in the bed or on the beach for an extended period of time) then it will be broken down. I remember that Lee Hayworth at one point mentioned that an elite body-builder could lose 10kg in a sole week of illness – cant vouch for it, but I’d take his word. So unless the calories are reduced accordingly, this is a lot of “extra meat” that is consumed, and that will at the very least contribute to Mehdi’s aforementioned caloric excess.

Of course it does not really matter – at the end of the day we probably all agree that an athlete who changes his or her training dramatically needs to be very careful not to get fat, for whatever reason, but that two weeks of hols are maybe not that dangerous.


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