Evolutionary theory, including all those sub-fields where evolutionary is a modifier, is well on its way to becoming a tool of pseudoscience in performance and nutrition. “Evolution” is invoked not only to explain, but to justify things like behavior, moral judgements, and yes, even what we eat and how we train.
Evo-psych is a common transgressor, popular among nerds as it tries to “explain”, among other things, why men and women behave in certain ways. Thanks to serious methodological issues and the inherent problems with figuring out causality in complex biological and cultural interactions, it’s hard to take seriously. Such pseudo-explanations have more in common with making things up than with serious investigations into the “why questions” of human nature (even being charitable, it’s hard to see how essential biology and social construct are disentangled).
There’s no denying that, insofar as our current biology can be said to have evolved “for” the purpose of survival (we can excuse the teleological language), evolution provides a kind of explanation for why things happen to our bodies as they do.
Only in broadest terms, however. Adaptationism remains controversial, meaning that our biological traits need not be fitness-enhancing “designs” but may just as easily be historical accidents, or as epigenetics is currently showing us, shaped by the environment. Evolution explains how, in a global sense, rather than explaining why in specific terms.
Can’t lose fat? Body getting ready for starvation mode, because evolution. Can’t put on muscle? Body doesn’t want to add muscle because muscle is expensive and evolution. It might be fun to blame this stuff on evolution, but this should not be confused as any meaningful insight into how your body works, and it certainly has nothing to say about how we should address it as real-life solutions.
“Because evolution” is not the right answer to questions of training and nutrition.