Yes, improved cardio results in a lower resting heart rate, which reduces BMR. Resting heart rate only gets as low as the 50s though, then it stops going down.

Yes, improved cardio results in a lower resting heart rate, which reduces BMR. Resting heart rate only gets as low as the 50s though, then it stops going down. > Your body has a weight set point like it has a temperature set point. And more recent studies have shown how to change it. Eat at a moderate deficit for 4 months, then take up to 2 more months carefully eating at maintenance. Rinse and repeat to keep losing weight. This avoids the problems you are talking about. But if someone has 100 lb to lose they don't want to hear "lose 1 lb a week for 4 months, then don't lose any weight for 2 months, repeat for a few years." Adherence to such a plan will be terrible, but it'd work. Calorie cycling, as described in the video I linked to twice in this thread, also avoids the problems, and Dr. Mike explains how calorie cycling prevents the problems with hormone levels that a long term deficit can create. Also > Yeah, you use about 100kcal running a mile, so 26mi gets you around 2/3 of a pound of fat. This is why I'm not a fan of running. I have recorded workouts (HR chest strap) of me burning 500 calories / hour. Then again when I'm in shape (currently recovering from a rib injury....) I spend an hour with my heart rate in the 150s to low 160s on a 3-1 interval cycle. Also it won't be 2/3 a lb of fat, it'll be carbs at first, some fat, and at those calorie burn numbers, some muscle mass as well. (This is where the keto people jump in, but sadly research studies on high level athletes who are long term keto adapted doing intense stuff are hard to come by)