This works because BMI is a function of weight divided by height squared. If you maintain the weight while he or she is still growing, an increaseJust Keto of a few inches with the weight remaining the same will cause the BMI to decrease greatly.But what about an adult or a child who is no longer growing in height? Most doctors and dietitians recommend losing 1 to 2 pounds per week as a rate of safe weight loss. Others, recommend losing only one pound per month.