Muscle mass can be gained through moderate to intense strength training several times each week, coupled with taking in extra calories.

For each pound gained as muscle in a week, you will need to consume about 500 extra calories each day. The extra calories should come from a variety of foods: milk, meat, fruits, vegetables, and grains.

The key is to be consistent. Eating three meals a day with snacks in between is an essential part of gaining lean body mass. If you sleep in and skip breakfast, you miss a chance to add extra calories to your diet.

Eat enough to satisfy your appetite and then try to eat a little more. This can be done by:

eating larger than normal portions

eating an extra snack or meal

drinking commercial liquid meals or milkshakes with regular meals or as snacks.

Some good snacks if you are trying to gain weight are:

peanut butter sandwich

low-fat milkshake (with skim milk and low-fat ice cream)

dried fruit

cottage cheese

pasta with sauce.

Commercial protein supplements will not help you gain weight and will probably add too much protein to your diet. If you need a liquid supplement, make sure it provides the extra calories you need as carbohydrates, not protein.