The statement "you have to eat every 3 hours to lose weight" is definitely false. The need to eat every 3 hours was touted for many years as the best way to lose weight, stemming from the belief that it would boost a person's metabolism. It was assumed that if you ate many small meals throughout the course of a day you would constantly be stimulating your metabolism and therefore burning more calories. However, in recent years studies have shown this is not the case.
