People often think that burning tons of calories through exercise and consuming very few calories through diet can result in rapid weight loss. Although this may work at first, it may limit your weight loss after the first week or two. You needs you to consume enough to fuel your body's internal functions and provide your muscles with energy during exercise. Failure to do this can cause your body to start shutting down.
Very Low-Calorie Diet
Your body gets its energy from the calories you consume. If you do not consume enough calories to meet daily energy needs, your body enters starvation mode, in which it slows down its internal processes to save energy. This slowdown decreases the number of calories you use each day and increases the amount of fat your body stores, explains Barbara Mendez, a nutritional consultant and registered pharmacist in New York City. As your metabolism slows and you store more fat, your weight loss may slow, stall or reverse.
Exercise increases your body’s need for calories. Any amount of exercise done while you're following a very low-calorie diet may cause your body to enter starvation mode. Your body typically turns to fat for energy while in starvation mode, but exercise may require a rapid source of energy that your body gets by breaking down muscle., making your body more susceptible to injury and decreasing your metabolism even further, warns Patricia Pierce, of the Rehabilitation and Exercise Science Department at Slippery Rock University in Pennsylvania. In addition to limiting your weight loss, the combination of excessive exercise with a very low-calorie diet may cause life-threatening health conditions.
Eating disorders, such as anorexia or bulimia, may result if you follow a very low-calorie diet or exercise excessively for too long, warns Dr. Luisito Dingcong, a Clearfield, Pennsylvania, psychiatrist. He says that when someone goes to these extremes to lose weight quickly, she can become obsessed with her weight and appearance. If you exercise for hours each day in an attempt to maintain your weight, feel the need to control your calories by fasting or binging and purging or experience feelings of depression or anxiety when you do not follow your diet or exercise regimen, consult a medical professional.
Healthy Weight Loss
Healthy and sustainable weight loss requires a commitment to moderate exercise and a reduced-calorie diet, but within limits. An intake of fewer than 1,200 calories a day for women or 1,500 calories a day for men is a very low-calorie diet. If you exercise daily, you need even more calories than this. Consult an exercise physiologist or your doctor to determine an appropriate calorie intake, based on your age, gender, weight and exercise routine.
The American College of Sports Medicine says that you may need 60 to 90 minutes of moderate intensity exercise on most days of the week to lose weight. Do not plan to exercise more than this unless you're under the direction of a trained professional.