Eli5: the larger the creature the slower the metabolism; so why do our metabolisms speed up when we gain weight?
In: 4
it’s slower relatively. not absolutely. as you gain weight, your metabolism goes up. but your metabolism per lb/kg of weight goes down. so it doesn’t scale lineally.
As the body size increases, you lose less heat. This is due to surface area, but every cell in animal bodies is like a little light source. It requires energy to keep itself alive.
So if you gain fat, those cells require energy to keep alive. Storage isn’t free. Its while your TDEE drops as you weigh less.
With regards to “the larger the creature the slower the metabolism”; that only applies to calories per pound; not total calories spent. For example, a hummingbird – often used as a high-metabolism animal – consumes as much as 8 calories per day for a 3 gram body weight: about 2 calories per gram. In contrast, an adult human at about 60 000 grams only consumes about 3000 calories – about .05 calories per gram. And adding muscle makes you more efficient: 1000 grams of muscle only adds about 5 calories per day – .005 calories per gram, or about 1/10 of what baseline is (which is high because the human brain uses a huge amount of extra calories).
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