And I should add protein is good to eat to promote gain of muscle.
Sometimes not eating what your body needs does that, especially if you're skipping breakfast. When your body doesn't have fuel from food, it will burn muscle, and muscle is needed to aid in weight loss. Eat normally, just exercise portion control. I find people who try to really watch what they eat and have a splurge day or limit themselves severely end up having splurge days, over splurge, which is also counterintuitive. You need carbs, some fat, etc., to have a balanced diet.