Weight loss & gain
The time to be concerned about weight loss or gain is when the cause isn't readily apparent. That's when you should see a physician.
Dieting is the practice of eating food in a regulated way to decrease, maintain, or increase body weight, or to prevent and treat diseases such as diabetes and obesity. Dieting to lose weight is recommended for people with weight-related health problems, but not otherwise healthy people. As weight loss depends on calorie intake, different kinds of calorie-reduced diets, such as those emphasising particular macronutrients, have been shown to be no more effective than one another. As weight regain is common, diet success is best predicted by long-term adherence. Regardless, the outcome of a diet can vary widely depending on the individual.