Want to Lose Weight? Calories Should Not Be Top Priority (Here's What Should)! by Heather Frey
If you grew up in a time when calories ruled, when all that mattered was how much you ate rather than what you ate, then you may actually be patting yourself on the back for starving yourself all day. The truth is, you're simply teaching your body how to conserve calories, not burn them. Our bodies are clever machines designed for survival. Your body isn't going to give up all its protective padding (AKA fat) so easily, especially if it thinks it won't get any nourishment most of the day.
If you want to lose weight and gain muscle, you have to EAT. You have to reprogram your thinking and tell yourself you're defeating your purpose, especially if you're working out. You can't get fit without food. You have to put into it what you want out of it. Think quality (nutrients) of food, not calories.