Sometimes being "too skinny" can be just as difficult a problem to solve as being "too fat." Achieving a desirable body weight and shape involves changes in lifestyle — including diet, exercise and behaviors that support health. Your doctor can get you started by providing you with healthy goals and tips.

Eat a well-balanced diet that includes whole grains, vegetables, fruits, low-fat dairy and lean protein sources, such as fish, poultry, meats, beans, legumes. Fats and sweets can also add extra calories. But don't eat them in great amounts. Eating three meals a day plus between-meal snacks on a regular basis helps ensure the balance and variety you need to gain weight. You don't need sports supplements, such as protein and energy shakes and herbal supplements. Food is the preferred fuel for building muscle. Keep in mind that heredity influences body shape and weight. If your parents and siblings are slender, you're more likely to be slender too.

Strength training will help increase lean muscle mass, and increased lean muscle will add weight. Develop a program of exercises that includes all the major muscle groups in your upper and lower body, and trunk. Proper technique is key. Select a weight that tires your muscle at about 15 to 20 repetitions when first starting. As you progress, your goal should be 12 repetitions. One set two or three times a week is all you need. Avoid working the same muscle group on consecutive days.

Remember, changes in weight and body shape take time. Also, progress includes more than just pounds.