eli5: How does fat gain/loss actually work?

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It’s my understanding that most fat (re: loss) is essentially metabolized and exhaled as carbon dioxide. What I can’t wrap my brain around is that even after eating a calorie surplus the weight doesn’t INSTANTLY appear – maybe after a heavy meal, but if it’s something just really calorie dense this isn’t the case. But the calories have been consumed so I don’t understand why the weight doesn’t reflect that instantly. So it seems like the fat gain side of thing might be actual magic.

In: Biology

4 Answers

Anonymous 0 Comments

When you eat something, the weight is in your gut as you digest it. Your daily meal is maybe 2-5 pounds total. Then you pee and sweat and poo and breathe and that 2-5 pounds mostly leaves you.

But if you eat excess, your body may take a small amount of that daily food intake and store it away “for later” as fat. Maybe an eighth or quarter pound here or there or less.

Most people move up and down 2-10 pounds per day in weight depending on hydration, food intake, etc. The actual fat gain is a tiny fraction of that but say after day it can add up.

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