To lose weight you must create a calorie deficit. Simply stated, this means you must expend more calories than are consumed. From a mathematical standpoint -- a pound of body fat equals approximately 3500 calories -- so to lose 30 pounds in 45 days -- you must create an average daily deficit of 2,334 calories. This calculated as follows: 30 pounds times 3500 calories per pound, equals 105,000 total calories. 105,000 calories divided by 45 days, equals a 2,334 calorie deficit per day. Since you should not restrict your caloric intake by more than 700 to 1000 calories per day, this results in a need to burn at least 1,300 calories a day through exercise. If you do not wish to diet you must burn the entire 2,334 average daily calories through exercise.
Switch out high-fat foods for low-fat varieties, as fat has more than twice the calories of either carbohydrates or protein. Start by substituting margarine for butter, and skim milk for whole.
Leave alcohol off the menu, as it adds seven calories per gram.
Eat smaller, more frequent meals. Try eating four to six times a day. The thermic effect of food, or energy used for digestion, in itself is an effective means of burning calories.
Choose an aerobic activity that burns a high number of calories -- such as basketball or cycling (approximately 750) -- or rowing or running (over 1,000) -- and perform it for two hours a day.
Lift weights. Weight training not only burns calories, it strengthens muscle tissue. This will raise your metabolism and burn more calories, even when your body is at rest. Many people are under the misconception that because lean muscle tissue is denser, and therefore weighs more than fat tissue, that lifting weights will be counter-productive to losing weight. However, gaining weight, either fat or muscle, always requires creating a calorie surplus.
Consult a physician before beginning any strenuous exercise program.