No when they eat to little they don’t fuel the metabolism to burn off the fat and they stay status quo. You really have to know what to eat, when to eat and how to eat. That’s why fad diets don’t work and you wind up gaining everything back plus more. Because you lose mostly water and muscle and not fat to begin with. You lose too much to quickly so you shock your system. And then when you try to eat normally, your system is so hayward it is sending out mixed messages all over the place.
Protein is needed to fuel your metabolism. Breakfast is the most important meal of the day because it gets your metabolism going first thing in the morning. If you skip breakfast your metabolism isn’t kicked into gear until you actually eat something with protein in it. That is why you feel sluggish, tired and not up to par.