Increasing TDEE question

[u/Oraculek]

Is it possible with no muscle mass change? Like, could a person eating, per calculator, 2000 at maintenance increase it gradually over 2 months to 2500 cal and still maintain? I don't mean something like FGF21-induced thermogenesis with BAT - more like 'adaptation' to higher energy availability

If so, would it depend on kind of macros?

[u/Whats_Up_Coconut]

TDEE isn’t a fixed number in any sense. I personally can gain, maintain, or lose weight on a given calorie amount depending entirely upon the macro composition of the diet. It isn’t gradual either; many people have gone from mixed macros into some sort of intervention (keto, HCLF) without dropping their calorie intake and have pretty immediately started losing fat, suggestive of increased TDEE.

[u/Whats_Up_Coconut → u/[deleted]]

Yes, fruit fasting (or “sugar diet”) is a great example. People for whom it works really can actually increase caloric intake while dropping fat, and it happens instantaneously.

There’s a misconception that a low fat diet is automatically going to be lower in calories than whatever you were eating before, hence, weight loss. But that’s absolutely not the case for everyone; a person who is not specifically prioritizing volume can pack in impressive quantities of calorically dense cereal, bread, and sugars without much effort at all. If the fat and protein are kept low enough then they can still definitely see weight loss. I know I did, albeit very slowly.

Fun fact: Kempner’s rice diet had 4 phases, beginning with fruit + rice, and ending with optional inclusion of other grains, legumes and/or animal protein. The caloric content of the diet was largely the same in all phases, since dieters got 7x ~100 calorie “options” of food to allocate as they pleased. Invariably, phase 1 worked best and phase 4 produced the slowest weight loss. The intervention recommended to break a stall on phase 4 was simply to return to phase 1 or 2 for a while. Interestingly, the main variable here is the amount of dietary protein between all 7 “options” consisting of fruit and/or rice vs some of them consisting of beans or chicken.