The Atkins approach is a low-carb, high-protein diet that claims to "turn your body into a fat-burning machine" by limiting its production of glucose and forcing it to use stored fat as a primary energy source. Your diet affects your metabolism, but not as much as you may think -- up to 80 percent of your metabolic rate is based on calories burned at rest, called your "basal metabolic rate" or BMR.
Understanding Metabolism
You burn energy constantly -- even while you're sleeping -- for basic bodily functions, such as breathing. Your total energy expenditure is called your metabolism, which is broken down into three parts: BMR, movement and digestion. Your BMR uses between 50 and 80 percent of your energy; up to 20 percent is used for physical activity, and between 5 and 10 percent is used to digest food and convert those foods into energy. The Atkins high-protein approach to weight loss can increase this number, because your body uses more calories to digest protein than any other nutrient.
Protein, Digestion and Metabolism
About 4 percent of the calories in fat are used for digestion, and 6 percent of the calories in carbohydrates are needed to process carbs. Protein, on the other hand, requires 30 percent of its calories for digestion. In other words, if you eat 100 calories of fat, you must burn 96 calories -- any calories consumed but not used for energy right away are stored as fat. A total of 100 calories of carbs leaves you 94 calories to burn, while 100 protein calories only gives you 70 calories to use or have stored as fat. Another way to look at this -- protein raises your metabolism by 30 percent.
Muscle Vs. Fat and Your BMR
The Atkins diet may also help raise your basal metabolic rate, because muscle burns more calories than fat, even at rest. The Atkins diet burns stored fat, helping you to lose body fat -- not just water weight. Many diets that cause rapid weight loss can also cause the loss of lean muscle mass, especially low-calorie diets. Because of the high protein intake on the Atkins diet, lean muscle mass is preserved. Losing fat and gaining muscle will increase the rate you burn calories, even while you sleep or watch TV.
Warnings
Although the Atkins weight loss program has been used since the 1970s, there are no long-term studies about the potential negative side effects of a low-carb diet. A one-year study published in the "Journal of the American Medical Association" demonstrated that people lost more weight following the Atkins diet than the Zone or Ornish diets. However, Dr. Meal Barnard, president of the Physician's Committee for Responsible Medicine, or PCRM, states that the Atkins diet includes too much cholesterol and saturated fat -- and may be too low in fiber and essential nutrients. The PCRM website states that "individuals who follow low-carb diets are therefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall."
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