I am sure it's personal, but when I fast 24 hours (once per week), the next two days I look for less food, to the point that I can skip lunch without noticing.

The big deal for me is not eating stuff with flour (starch?) or sugar.

I already eat healthy, although I switched from chicken to a full protein tofu that's low on calories and that has been a blessing for protein intake (along with egg white). I can eat 60g of protein at lunch in about 350 calories.

That gives me everything I need for the gym.

My snack is apple with a teaspoon of pure pistachio butter, which calms down my desire for sweets (I love pistachio)