With regards to Constrained TEE (Total Energy Expenditure)—Herman Pontzer hypothesizes that the body adapts to increases in daily physical activity expenditure by reducing energy expenditure on other tasks (e. g., immune response, reproduction, somatic repair/maintenance), maintaining TEE homeostatically within some narrow range.
In theory, the body COULD also reduce energy expenditure on immune response, reproduction, somatic repair/maintenance in response to decreases in calorie intake—thereby ALSO constraining TEE.
I’m beginning to think that Pontzer’s hypothesis is not really accurate.
We already know that drastically reducing calorie intake DOES in fact reduce energy expenditure on immune response, reproduction, and somatic repair/maintenance. Yet, experience tells us that reducing calorie intake is much more effective than increasing physical activity with regards to fat loss. There’s something else going on to explain why the body so readily constrains TEE in response to increases in physical activity compared to decreases in calorie intake. I’m not sure what can explain this discrepancy.
Even though we don’t have a bioplausible mechanism for why reducing calorie intake is so much more effective than increasing physical activity with regards to fat loss, we still know that the former is much more effective in improving endpoints (fat loss) we actually care about. That’s what matters.
I usually only recommend 30 minutes of moderate intensity cardiovascular exercise. I think there are benefits to cardiovascular exercise: psychological, CV benefits, improves resistance training work capacity. However, with multiple lines of converging evidence, I find it difficult to recommend greater than 30 minutes of cardio, especially when the athlete is already resistance training (assuming their goal is getting lean as fast as possible while maximizing muscle retention).
During my first prep, I worked with a coach who ramped up my cardio to 2 hours/day (this is IN ADDITION to resistance training). We started at 30 minutes/day and increased cardio in increments of ~15 minutes. We never implemented changes to diet and cardio at the same time. After every incremental increase in cardio, then waiting a couple days to monitor changes, the needle never moved. The only intervention that moved the needle on fat loss was decreasing calorie intake.
Also, see below:
“In humans training to run a half‐marathon, TEE plateaued (black line) as workload increased over the course of a year rather than increasing linearly as predicted by Additive TEE models (gray line). Men and women in this study also exhibited a small decrease in BMR (dotted line).”
Look at where the TEE is capping out. At a measly 30-40 minutes of running/session.
Lastly, decreases in NEAT do not explain why Constrained TEE occurs:
“Tests of the constrained TEE hypothesis suggest that behavioral changes are insufficient to account for the observed stasis in TEE (Pontzer, 2015a; Pontzer et al., 2016b).”