Being overweight or obese will cause or aggravate many conditions in the body. It pressures the heart and impacts every organ and tissue. This can give you a lower quality of life and will shorten your life.
Although there are legitimate illnesses that cause you to be overweight, most people can be helped by using a program to get rid of the overweight condition. A good, safe program has a weight loss phase, plus recommends making longer-term changes in eating and lifestyle to maintain that change. This includes exercise. Making no changes in diet and lifestyle will ensure that the weight will come back!
Programs need to be safe. Safe programs should have adequate calories, protein, fats, carbohydrates, vitamins, and minerals. This avoids many health conditions associated with very-low-calorie programs. Any program with less than 1000 calories would be unsafe. I have seen these types of programs and noted 2 main things with those that go on them; much higher rates of the gallbladder, and other conditions, PLUS a much higher rate of gaining the weight back, and then some!