A friend spoke about how days when he overeats after a workout, he's super happy, and the next day wakes up really refreshed.

I can see how it's tempting to interpret this as the body teaching you

I believe that imputing any morality to this at all is wrong. There is no deep spiritual or ethical meaning to this. It's just the product of selection.

Biology could, without any physical problems, let you feel that happen at any time, or as a response to any kind of stimuli. For you, the organism, that would be fine (or could be made to be, with matching biological changes elsewhere within your body). The only potential problem would be that it'd change how you reacted to responses and your status under evolution.

So:

• You could be that happy from every meal
• Some people actually are that happy (variations around the space you identify your self with already exists in humanity)
• Attempts to stop people from feeling that happy are wrong
• But nature is also pretty wrong here. Evolution is
• The next natural step is to get out from under the cruel personality/mood selection which our ancestors went through

This is covered in the old Yudkowsky story: Three Worlds Collide