TL;DR I began to notice, every time I was immersed in warm temperature, whether central heating at home, thick clothing, hot weather, it always made me drowsy and all I wanted to do was sleep. Because I did this so much, my metabolism slowed drastically, and I began to gain weight rapidly, even though I was somewhat calorie deficit.
I just didn’t make the connection between raised body temp / warm air, until, as fate would have it, I noticed the exact opposite would happen when immersed in cooler temperatures - yes, my energy levels went through the roof.
I don’t even know if this is well known among sports athletes or anything, but I looked into this, and basically, when our bodies overheat we release a substance called prostaglandin D2, which causes us to become drowsy, so we become inactive and allow our bodies to cool to core temperature.
When immersed in a cold environment OTIH, PGD2 is suppressed, and our bodies start releasing metabolites, and we start entering into fat burning mode to make us become more active so we can generate warmth and return to core temperature.
Since figuring this out, weight is totally dropping off me, but the key is to try stay borderline cool, and you’ll never feel tired. Of course don’t do this while sleeping, I just mean during your daily routine.