This diet is for those who need to achieve a healthy weight. This is one of the most important goals for those who are underweight. However, it is not the only reason that makes people want to gain weight, some may want to gain muscle mass to play sports or they may be recovering from some illness.
The term "underweight" is typically used to describe an individual who is not within a healthy weight range and has less body fat than is necessary for maximum well-being.
Although there are some people who have a naturally thin body type, those who are underweight as a result of poor nutrition or for a health issue have a significant risk of developing certain health problems.