Right now I'm reading stuff about how women's muscle protein synthesis ability differs from men's. Have not done further reading yet on Keith's concern, and have not seen anything along those lines studied in a weightlifting population, specifically -- maybe Keith will post some links. Here is one I read yesterday, which the authors termed an overview of recent results of Calorie Restriction [CR] interventions in humans [dated 2017]:
Does eating less make you live longer and better? An update on calorie restriction
Under the heading "Long-Term CR [calorie restriction] Interventions in Humans" is this:
If I recall right, TNF-alpha is a marker of tumor activity or possible tumor generation. There's a sentence where they say that participants were consuming 1800 kcal/day for "an average of 15 years," and were careful to keep diet quality high and meet all nutrient needs.
Later on under the same heading, they say:
Since we are encouraged to consider our bone mass and health throughout our lifespans, I'm not sure it's valid for the authors to say that bone mass concerns "might limit the application of [Calorie Restriction] for older persons," but not for young and middle-aged people. And I'm not sure I want to rely on rodent studies re the health of my bones -- being an older female, myself. Bone density is one of the reasons I'm squatting and deadlifting, right now.
I should note that I have no statistical chops, or familiarity with the quality of various journals in which these things are published or with the work of the various lead researchers. So I have very limited ability to evaluate the quality of the research -- just what I see in the four corners of the papers, themselves. If anyone with statistics or research design knowledge wants to chime in with observations about the quality of the work, or happens to know that particular papers have been superseded by later work with different results, I'd be happy to hear about it!