A point of clarification: The study was done on HUMANS. Not rats.
They did a previous study on rats, which led them to try a study on humans.
I think it’s true that if you’re heavier, you will have a higher TEE (see link below for definition), and if you’re lighter, you’ll have a smaller TEE. This is what makes any measurement of this fraught with error: you have to take this into account.
The theory behind the study is that you have a “set point” that takes this into account: as you get heavier, you burn more calories. They gave weighted vests to humans to try and test this. (Note: too bad they didn’t use DEXA scans. Or put them in one of those metabolic chambers. Probably too much money.) And the humans with the heavier vests lost more fat mass.
Anyway, I find studies like this interesting. Not only have I asked for a cold vest for Christmas (would use this to active brown fat), but I could add some weights and see what happens.
If we ignore extra calories (likely to be tiny, see link below) from carrying the vest, it’s possible there is an increase in TEE. Whether that’s caused by a “set point” or not is hard to tell.
Link for TEE: