Comment by tremon

Anecdotally, this has been my experience as well. I tend to think of my base metabolic rate as the integral over my physical activity over the last N years (it used to be N=5, but even that window is way too small I think now). Point being, you can be inactive for a long time without a meaningful change in body fat/weight, but eventually your body adjusts. Or rather, the first gain in body fat is offset by the loss of muscle weight. Once you're at a slower metabolic rate and less muscle, exercise becomes more difficult and it takes years of consistent activity to raise your metabolic rate again.

I'm not sure how base metabolic rate relates to incidental energy expenditure. My gut feeling is that every body has its own limits on energy expenditure, and max TDEE doesn't need to correlate directly with base metabolic rate. That's why I mentioned the integral above. I tend to think of $TDEE_{max} \simeq MBR_{base} + E_{available}$ but $MBR_{base} \simeq \int_{t=-5}^0 TEE(t)$ -- and in my experience, weight loss correlates more with base metabolic rate than with caloric intake ($E_{available}$).