This week’s Iron Culture goes into three influences on metabolism and the latest research on to what degree they actually matter–age, sex, and individual differences. Which, as I type that, I realize is kinda obvious from the title. But hey, my seventh grade English teacher taught me to have a topic sentence, and that’s what I’m gonna deliver! Anyway, back on topic, this is mostly an episode with Omar shooting softball questions at Eric and then Eric waxes scientific on each potential influence on metabolism, and there’s some good information in there!
The first section on the influences of age on metabolism is another discussion of the recent Pontzer/doubly-labeled water studies that have been getting so much attention (including from me, here and here). Eric summarizes the data as showing that basically age isn’t a major factor in our metabolic rates between the ages of 20-60; however, reduced activity and loss of lean body mass may explain the changes we witness of increased body fat and less flexibility in eating choices to maintain the same relative size.
I don’t know if I consider this information comforting or frustrating. I really appreciate Omar’s perspective when he comments on the coaching aspect of utilizing this information with clients. There’s a recognition that older clients will still have more hurdles–a busier life, more demands from family and work, likely increased risk for injury and chronic pain, more limitations to movements, etc. All of those potential increased challenges, and then if we want to maintain, we need to potentially work harder to do it. On the other hand, it gives me new reasons to roll my eyes at my mother or my friends who tell me I needn’t work so hard because I’m “aging and my body is going to change anyway.” There’s this acquiescence to some kind of inevitable decline that I think is not necessarily . . . necessary. My regular readers will know that I’m totally on board with fitting my lifting and other goals into my life. I’m not at all a go hard or go home kinda person. AND, I don’t like using my aging (or disabilities) as an excuse to stop pushing myself. It’s always going to be a balance between what I want and what is possible, but I don’t want to cut myself short and assume something isn’t possible. So, in that way, it’s good to know that at least in this arena, the inevitable increase in my age is not a barrier in and of itself.
The next part of the discussion on sex differences I think would have benefited from a female perspective to join the conversation. I appreciated the information that Eric brought about metabolic differences between the biological sexes as explainable almost entirely due to muscle mass and body mass differences. I think it’s really powerful to know that pound for pound of lean mass, women are showing that they can be as strong as men. AND, I would have loved to hear a more thoughtful discussion on why we witness such dramatic differences in strength, including differences in physical activity participation between girls and boys, men and women. Going back to the previous factor of age, if we need to maintain being active to keep our muscle mass, we need to explore the barriers to physical activity which are clearly disproportionately impacting girls and women. If we want to explain the differences we see in the real world, there’s more context to bring to the table.
The final point on individual differences is an important point, and I think more could be said to suss out all the ways we are always estimating, overestimating, and underestimating our own and other people’s potentials based on use and misuse of averages and other estimates. Age and sex are two of many factors that make these estimates sometimes tricky to put into individual contexts, and honestly, I think it’s part of the appeal of always learning more about these topics! I’m always trying to figure out how I fit in, where I’m average and when I’m an outlier.
An interesting and thought-provoking episode overall. I’d love to hear what connections you make while listening to it! Does it change your thinking about metabolism, age, sex or individual differences? And do you think my seventh grade English teacher would be proud of me today? Let me know below.
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