Lactose intolerance does not necessarily affect body weight. Lactose intolerance merely causes symptoms like diarrhea, abdominal pain, and bloating when consuming regular formula or cow's milk. If one consumes hydrolyzed formula or lactose-free milk powder, these symptoms, such as diarrhea, do not occur, and nutrients can be fully digested and absorbed. By ensuring adequate nutrition, this can lead to weight gain and obesity, rather than causing a person to be underweight.