The Calorie Limit For Weight Loss

Calorie control makes up the core of any weight-loss program. Even if you work out at the gym every day, eating too many calories will lead to weight gain. Too few calories, however, can put your body in starvation mode, a biological state in which your body takes its nutrients from your muscle, bone and fat tissue. The American College of Sports Medicine (ACSM) recommends never eating less than 1,200 calories a day if you're a woman or 1,800 a day if you're a man.

Macronutrients

Your body uses the macronutrients in your diet for optimal function. These nutrients include the protein, fats and carbohydrates in the meat and vegetables you eat. According to a 2009 press release by the Harvard School of Public Health, a long-term study showed that caloric intake was the only factor in weight loss and that the ratio of protein, fat and carbohydrates in the diet played no part. Participants in the study tried to meet a 750-calorie deficit each day and exercise at least 90 minutes per week.

Time Frame

In order to lose body fat without sacrificing muscle, your caloric intake must nourish your lean body mass while forcing your body to take some of its nutrients from body fat. The University of Illinois at Urbana-Champaign website recommends setting your calorie-reduction limit between 500 and 1000 calories below the amount you need to maintain your weight. This amount will result in a rapid weight loss of one to two pounds per week without risking starvation mode.

Total Daily Energy Expenditure

Your upper calorie limit equals your basal metabolic rate (BMR) plus the calories you need for daily activity. Your BMR is the number of calories your body needs at rest to carry out essential functions such as breathing and keeping your heart beating. Consuming more calories than you need for your total daily energy expenditure causes your body to store the extra calories as fat or, if you're a bodybuilder, as muscle. Even sedentary individuals burn some extra calories through essential processes such as digestion.

Unhealthy Weight Loss

According to the University of Cincinnati Net Wellness site, consuming below 50 percent of your caloric needs puts your body in starvation mode. Obese individuals may lose a lot of weight from body fat while in starvation mode, but leaner individuals will lose weight from lean tissue, including vital organs such as the heart. Because a significant portion of the weight you'll lose on a starvation diet comes from water weight, you'll regain these pounds right away when you start eating normally again.

Considerations

Controlling calories determines the amount of weight you'll lose, but exercising accelerates weight loss by depleting your body's carbohydrate stores and burning off body fat. Working out allows you to lose weight while eating more than you would if you didn't work out, and it keeps your heart and circulatory system in shape. The ACSM recommends both strength training and cardiovascular exercise for optimal health and weight loss.