When you're underweight, your chest may appear slight or delicate, so it's not uncommon to want to build size in this region. Men with large, muscular chests look defined and strong; women with voluptuous breasts fill out a bikini top or a strapless dress. Gaining weight can help create a fuller looking upper body, but you can't guarantee extra weight will migrate solely to your chest.
Extra calories and a total-body strength training routine can help you pack on pounds. Including several exercises to target your pectoral muscles can also help build greater size in the chest. If you're a woman, though, this muscle increase won't necessarily increase your cup size.
Calories for Muscle Gain
The optimal way to build a larger chest and an overall healthier looking body is to add muscle mass by weight training and eating a surplus of calories. Consuming 250- to 500-calories a day in addition to the calories you need to maintain your weight helps you put on the maximum 1/2 pound of muscle per week. If your body packs on fat easily, keep to the lower end of this range.
Many of those added calories should come from larger servings of protein and protein-rich snacks. Your daily intake should be about 0.8 grams of protein per pound of body weight.
Exercise to Build the Chest
Just adding calories won't enable you to build muscle mass, nor will it add fat tissue exclusively to your breasts if you're a woman looking to increase your bra size. Without exercise, about two-thirds of every pound you add is in the form of fat -- and this fat may go to your stomach, hips and thighs.
Weight training provides the resistance necessary to work the muscles so they use the extra calories you're eating to grow stronger and thicker. A total-body program that addresses every major muscle group maximizes weight gain and balance in your physique. Choose at least one set of four to eight repetitions of moves such as squats, lunges, shoulder presses, rows, curls and crunches. Use weights that feel heavy when you are doing the last one or two repetitions.
Because you're focusing on chest size, do extra exercises for the pectoral muscles -- including presses, flyes and pushups. Leave at least 48 hours between muscles worked to enable them to repair and grow.
Foods to Eat to Gain Muscle
A meal plan consisting of calorie-dense, whole foods supports your efforts at the gym. Choose starchy, high-fiber vegetables, such as sweet potato and winter squash, and whole grains for energy. Quality fruits that promote weight gain are bananas, papayas and pineapple. Protein sources that provide the amino acids you need for muscle growth and recovery -- as well as for health -- include eggs, chicken, turkey, salmon, flank steak, tofu and whey protein.
Have a protein snack after any of your weight workouts, including those focused on your chest. Suitable post-workout snacks that have quality calories could include a shake made of blended fruit, yogurt and whey protein; a turkey sandwich on whole-wheat bread; or a chicken breast with a sweet potato.
Realistic Expectations for Chest Size
Your basic body shape and size is genetically determined -- and this includes the size of your chest. Some body types are simply lankier and more slender than others. Although eating nutritionally dense foods and doing weight training can enable you to feel and look fitter, they may not give you a bodybuilder chest or a bigger bust size. Stronger chest muscles do improve posture and definition in your upper body to help you look your fittest possible.