Its not nearly that simple. A person's metabolism rate is not constant -- it varies greatly with activity level, intensity of activity, type of food consumed, and even the weather. Hunger can also vary greatly. A person's fat storage and fat utilization are also influenced by endocrine responses. Bottom line -- its almost impossible to get and remain thin by dieting. You can get leaner by exercising with enough intensity. However, its a lifelong commitment -- as many of us have painfully realized.