If you lose weight like this, you will. The time and amount of menstruation are determined by the secretion of estrogen. Our usual nutritional intake is the basis of providing estrogen. If you eat less, you will have less secretion and less or no menstruation. Obesity is because the daily intake is greater than the daily discharge, as long as it is less than it, you can lose weight. You can lose weight by dieting like this, but if you eat more, you will rebound badly.