Look for Caloric Liquids
Would-be weight gainers need to hydrate like everyone else. But plain water, with its zero calories, is not your friend and caffeine-containing beverages, which help hasten weight loss, are even worse. Go with sports drinks, shakes and smoothies, milk or fruit juice.
Add Pounds by Building Muscle
Creating lean mass is a healthier way to gain weight than packing on the flab, and the best way to build muscle is through resistance training. While weight lifting is the most common form of resistance training, it isn’t the only one. Resistance bands—basically large rubber bands—use your own body to create the resistance your muscles need to develop properly.
Eating every two to three hours can help you add weight without feeling stuffed. The key, of course, is watching what you put on your plate; shoot for an additional 200 to 500 calories a day by concentrating on healthful, calorie-dense foods such as nut butters, trail mix and avocados.