Assume a man weighs 200 lbs (30% body fat) and is eating maintenance calories. He adopts a lower food reward diet (or whatever is your preferred method to lower setpoint) in order to change his body fat setpoint to 10%. Going from 30% to 10% body fat, would take him to 155 lbs.
My understanding of setpoint theory is that the change in diet would spontaneously cause him to naturally consume the maintenance calories of a 155 lb. man instead of a 200 lb. man. This would be less calories than he was previously eating, so he would lose weight (fat) over time until reaching equilibrium at 155 lbs.
However, I believe BMR is primarily determined by lean body mass. 200 lb. man at 30% and 155 lb. man at 10%, both have 140 lbs of lean body mass, so wouldn't they have roughly the same BMR. And if his activity level stays the same, wouldn't maintenance calories also stay the same?
I think I could have been more clear in my question. Let me clarify, and sorry if this gets long. I think I am about 15-20% body fat (e.g., can see top 2/3 of abs but not bottom). I have been quite strict paleo (archevore) for about 1.5 years. I never had an issue with obesity and can't imagine my leptin/insulin signaling is majorly off. I know my current weight is likely "healthy," but I would still like to get my body fat % down lower. I understand the other benefits of paleo (better digestion, sick less often, hopefully lower future risk of disease, etc) are far more important, but I can't help my vanity. Originally, I was resistant (though not militantly so) to the food reward hypothesis:
I have since come around as it does seem to do a good job of explaining why so many very different diets can all result in significant weight loss. So, I am testing it out on myself and trying a lower food reward diet. I am eating only beef stew (pastured beef, potatoes, carrots, celery, tomatoes, spices, water in slow cooker). Plan is to try to do it for 2 weeks (currently on day 5) and reassess. I know such a limited diet may not be a good idea long-term. It seems to be working well as I am now naturally eating 2 bowls twice per day and generally feel quite satiated. My energy level is good (still lifting weights, running, etc.).
I want to get an estimate of how quickly I should expect to lose fat, but I find this hard to do directly for 2 reasons: (1) It is difficult to calculate how many calories I'm eating because I buy my beef locally from a small operation so there are no nutrition facts to tell me what % fat is in each cut and (2) It's even harder to accurately measure how many calories I burn each day. So, I was trying to find another way to estimate how quickly I should expect to lose fat. I recently read Richard Nikoley's blog post on food reward:
and I tried applying his methodology. E.g., my current weight is 160 lbs at 18% body fat (29 lbs of fat) and if this new diet will get me to my "ideal" body fat % (e.g., 10%), then I'll end up weighing 156 lbs. So I plugged both into BMR calorie estimator to figure out how much lower my daily caloric requirement would be at new weight, which would in theory tell me how much fewer calories I'm eating each day. Unfortunately, I quickly realized that daily caloric requirement is about the same because lean mass stays the same (assuming mostly fat is lost). This makes me question my understanding of the theory.
After reading the comments below and the linked postings, I think maybe the answer is just that I'm misunderstanding how this actually works. Perhaps the answer is just that at the lower setpoint, the body starts burning more stored fat which causes you to eat less calories. Once the setpoint is reached, the body backs off on burning extra stored fat and you go back to eating more calories to maintenance level. To me, this makes sense, but still can we estimate how much stored fat we'll burn off per day? Would different diets (e.g., varying levels of food reward) make this happen faster or slower?
I realize many on here get annoyed with the "how do I get a 6-pack questions," so I apologize for that piece, but I really am trying to get a layman's understanding of how this works.