While obesity is becoming a major problem these days, being underweight can also lead to major health problems. However, there are still many misunderstandings about the ways to gain weight safely. Some weight gain methods result in severe short and long term effects on health.
Putting on healthy weight is necessary for an underweight individual and may also be a goal for someone who is willing to build muscle.
In general, consuming more calories than the body burns may result in weight gain. However, the calorie intake necessary to achieve the target weight gain may vary from person to person.