> If you transform fat into muscle, you still have the same amount of the same atoms
No, you don't.
> and thus weight the same.
Yes, if you trade one pound of fat for one pound of muscle, weight is the same. But since fat has an energy content around 3500kcal/pound and muscle is, IIRC, around 750kcal/pound, that corresponds to more than a 2500kcal calorie deficit with no weight change.
> it's quite possible to eat at a deficit and gain weight
> since fat has an energy content around 3500kcal/pound and muscle is, IIRC, around 750kcal/pound, that corresponds to more than a 2500kcal calorie deficit with no weight change
Feel free to ask a friend with chemistry or physics background why this is completely wrong and goes against everything we know about matter and energy.
You can't create mass out of nowhere. If you transform fat into muscle, you still have the same amount of the same atoms, and thus weight the same.