To help teenagers gain weight safely, parents should encourage them to eat three meals and three snacks every day and consume calorie-rich foods such as butter, margarine without trans fats and other whole-fat dairy products, suggests the Center for Young Women's Health. Parents should also gradually increase meal portions; use canola oil, olive oil and other heart-healthy oils; and add items that make foods tastier, such as adding dried fruit to yogurt.
Parents may use butter and margarine on a variety of food items, including toasts, bagels, egg sandwiches and vegetables, advises the Center for Young Women's Health. Regular, full-fat or whole-milk yogurt and cheese help underweight teens obtain more calories than low-fat or skim dairy products. Drinking a glass of whole milk three times daily and eating regular ice cream are also good ways to gain weight.
Cashews, walnuts and almonds make great additions to salads, while peanut butter enhances the taste of crackers, celery and sandwiches, reports the Center for Young Women's Health. Parents should also try adding an egg or sliced avocado pieces to salads.
A weight gain of 1 to 2 pounds weekly is a safe target for underweight teens, notes the Center for Young Women's Health. To keep track of weight gain accurately, it's important to set clinic appointments in which doctors check weight changes of teens. Doctors sometimes prescribe supplements to speed weight gain.