An eating disorder causing people to obsess about weight and what they eat. Dieting is the practice of eating food in a regulated and supervised fashion to decrease, maintain, or increase body weight, or to prevent and treat diseases, such as diabetes and obesity. 3 days ago · to limit the food and/or drink that you have, especially in order to lose weight: You should be able to reduce your weight by careful dieting. Dieting is basically about breaking bad eating habits, reading labels when you shop for food, and eating small portions of nutrient-rich, balanced. With all the focus on dieting, how do you figure out what's healthy and what isn't? People diet for many reasons.