In a culture obsessed with thinness, it may feel strange to step on the scale and pray that the numbers have gone up, not down. If you're a skinny girl with an efficient metabolism, gaining weight and filling out can be difficult. A genetic predisposition to thinness is difficult to overcome, so you have to keep your expectations realistic. Talk to your physician about your expectations, then work with him to establish a diet plan that will meet all of your nutritional needs.
Eat more dairy. Enjoy yogurt, cottage cheese, pudding or ice cream for snacks and desserts. Add cheese to every meal. For instance, you might stir shredded cheddar into scrambled eggs, top a sandwich with sliced cheese or mix cheese into soups and casseroles.
Incorporate healthy fats into meals and snacks. Smear nut butter onto apple and banana slices or whole-grain crackers. Dip whole-grain bread in seasoned olive oil. Add oil-based dressing to baked potatoes, sandwiches and salads.
Choose your beverages wisely. Instead of water, choose 100 percent fruit juice, milk or vegetable juice. Whip up a smoothie with full-fat yogurt or cottage cheese, fresh fruit, juice and a scoop of protein powder. Avocado will make your smoothie extra creamy and add a lot of healthy fat and calories.
Eat strategically. When you sit down for a meal, eat the highest calorie foods first before your stomach is full. For instance, you might start with avocado slices and eggs at breakfast and finish with cereal if you are still hungry.
Eat frequently. You may have difficulty gaining weight because your appetite is small. Instead of forcing yourself to overindulge at meals, the Academy of Nutrition and Dietetics recommends eating five or six small meals per day. Space them out by three to four hours.
Get active. While it's true that you'll have to eat more to compensate for exercise, regular activity is good for your health and will increase your appetite. Strength training is a particularly effective way to add lean muscle weight. Sign up for a class at the gym or do free weight exercises at home. Don't neglect aerobic exercise either. Aim for a minimum of 150 minutes of cardiovascular activity per week.