Why do you regain the weight lost after being ill?

Question

Let’s say you have the flu and you lose 10 lbs over a week or so due to not being able to eat much. Why do you regain it, especially if you’re eating under maintenance/in a deficit normally?

It can’t all be water if you don’t eat for a week right? That’s a huge deficit.

In: Biology

Answer 1

If you’re down for a week the bulk of your weight loss is water and the rest is likely muscle degradation from lack of movement. Once you start eating and walking, you’ll start retaining water again in your lower half and your muscles will bounce back within a week or two.