How You Gain Weight
Weight gain happens when you eat more calories than you burn. A daily calorie increase of 250 to 500 calories per day will help you put on weight. You can't decide where that weight goes, however. Just as when people lose weight, your body's weight-gain tendencies depend on your genetics. Your general shape will stay the same -- so if you've got a fuller midsection and thin legs and hips, your proportions will be consistent as your whole body gets larger.
Eating to Add Weight
To gain weight, aim to eat more calories than you burn daily. Figure out your daily calorie burn using an online calculator that takes into account your age, size and activity level. Add about 500 calories to it to encourage a pound gain per week. Alternatively, speak to a dietitian about a good goal calorie intake for you.
Don't just add calories in the form of more chips, ice cream and junk food. Increase your intake of healthy foods, such as fruits, starchy vegetables -- such as sweet potatoes and corn -- whole grains, unsaturated fats, dairy products and protein.
An extra snack consisting of two slices of whole-wheat bread topped with 2 tablespoons of peanut butter and a cup of sliced bananas supplies about 500 calories. Alternatively, add extra calories to each meal. For example, at breakfast sprinkle an ounce of walnuts on your cereal; at lunch have an 8-ounce container of plain yogurt for dessert; and finish dinner with an 8-ounce glass of low-fat milk to boost your day's intake by 500 calories. The extra calcium in the dairy foods supports your body's growth and bone development, too.
Protein Powers Weight Gain
When gaining weight, aim to develop more muscle rather than just adding fat. Building muscle requires an increase in your caloric intake along with targeted training at the gym. A protein intake of about 0.55 gram per pound of body weight per day helps you recover from exercise and encourages anabolism, or muscle cell growth.
When you add more calories, make some of them come from protein. Use nut butter instead of butter on your morning toast to add about 7 grams of protein per 2-tablespoon serving; cook hot cereal with a cup of milk instead of water to add 8 grams of protein; add 1/2 cup of roasted, light-meat chicken to a salad for almost 20 grams of protein; or include 4 ounces of cooked ground turkey in marinara sauce or vegetable soup to add 22 grams. Protein-rich snacks that also help add calories are hard-boiled eggs, low-fat cheese or Greek yogurt.
Train Your Hips and Thighs
Strength-training your legs and hips can help develop the muscles there so that they're more toned and strong. A focused program may also help you to gain muscle, which will increase your lower body size. Plan to train your legs and hips at least twice per week on nonconsecutive days. Three days per week can give you better results.
If you're new to strength training, begin with just one set of eight to 12 body-weight exercises such as step-ups, squats and lunges. After a week or two, add weight in the form of dumbbells or a barbell. Gradually add sets and more weight as you feel stronger. Exercises to add in as you progress include hip hinges, single-leg squats, bridges and quadruped hip extensions, also known as donkey kicks. Build up to lifting weights that feel heavy after about eight repetitions to maximize muscle growth. Increase the weight when it feels manageable to complete your sets and reps.
Don't skip training the upper body and doing cardiovascular exercise just because you're trying to build leg and hip muscle. Perform at least one exercise for the back, chest, arms and shoulders when you train, and do short bouts of cardio, such as brisk walking, jogging or cycling for 20 to 30 minutes at a time, to keep your cardiovascular and respiratory systems healthy.
Overcoming Muscle Gain Obstacles
Some body types are genetically less receptive to muscle-building tactics. Recognize that any exercise and healthy calories you add are making you a fitter person.
Consider adding a post-workout protein snack to your diet to augment your work at the gym. A whey-protein shake or half of a turkey sandwich may provide you with a nutritional boost to improve muscle gain.
Drink plenty of water and get adequate sleep to keep your body healthy and help develop lean muscle mass. Teen girls need between eight and 10 hours per night, according to the National Sleep Foundation. As you grow into adulthood, the range shrinks by an hour to seven to nine hours per night.