You can thank Mom or Grandma for the size of your breasts. Their shape and makeup is largely genetic. You can't just target the breasts for reduction. Your body loses weight proportionally, not in isolated units. When you lose body weight all over, the fat tissue in your breasts will reduce along with fat throughout the rest of your body.
Breast Tissue Details
The breasts are made up of fat tissue as well as duct and lobule tissue, which facilitates lactation and breastfeeding. When you have a large chest, it's due to a greater volume of fat tissue. The cells in the fat tissue are just like fat cells in other parts of your body. As you gain weight, they expand, and when you lose weight, they shrink. If you're heavy and lose a significant amount of weight, you may notice the size of your chest reduces noticeably.
Spot Training Your Chest
Trying to reduce fat in just one specific area is a losing battle. You can't exercise away breast fat with pushups, chest flyes or shoulder presses. You'll build muscle in the pectorals -- the muscles behind your breasts in the chest wall -- but the fat tissue of the breasts is unaffected.
The one exercise exception may be in women who do extreme amounts of aerobic activity, such as endurance runners or long-course triathletes. Dr. Melissa Crosby, an associate professor of plastic surgery at the University of Texas MD Anderson Cancer Center, told "Shape" magazine that these women often have very low body fat levels, so their breasts become less fat along with the rest of their bodies. These athletes have a low body fat percentage -- their small breasts are simply a result of a very lean frame.
Lose Weight to Shrink Your Chest
Overall weight loss with moderate amounts of cardiovascular exercise, such as walking or cycling, and a healthy, low-calorie diet will help your whole body slim down, including your breasts. Weight loss occurs as a result of a calorie deficit between what you burn and what you consume. A 3,500-calorie deficit leads to 1 pound of fat lost -- not just from your breasts, but from your entire frame.
Estimate your daily calorie burn using an online calculator that factors in your size, age, gender and activity level. Then, subtract 250 to 1,000 calories from the number to figure how many calories you need to eat to lose between 1/2 and 2 pounds per week. If the resulting number makes your intake fewer than 1,200 calories per day, add more exercise to increase your burn, or revise your goals to lose weight a little more slowly. Consuming fewer than 1,200 calories can leave you nutritionally depleted and lead to weight loss that's too quick and unsustainable.
Although spot training isn't possible, strength training the major muscle groups -- which includes your chest, back, hips, abs, legs, arms and shoulders -- helps you accrue more lean mass throughout your frame. Lean mass takes more energy for your body to maintain, so the added muscle mass raises your metabolism and makes calories burn more easily.
Dietary Revisions for Weight Loss
Changes in your diet can yield weight loss. Focus on consuming mostly whole, unprocessed foods such as fresh vegetables, lean meats, dried beans and legumes, tofu, fish, whole grains and fruit. Skip foods made with refined grains, such as white flour, and added sugar. Sweetened beverages, including fruit juice, supply your body with excess calories that inhibit weight loss.
Devise your meals according to your calorie goals for the day. Try to distribute them evenly, because skipping meals or skimping during one meal can create excessive hunger that makes you binge later. Some combination of oatmeal, eggs, low-fat yogurt, fresh fruit and 100 percent whole-wheat bread make quality, weight-loss breakfasts. Lunch and dinner should feature a serving of lean protein along with a small portion of whole grains. Pile on fresh, watery vegetables seasoned with spices, herbs, citrus juice or vinegar; avoid heavy amounts of creamy dressing or sauces.