|MadSci Network: Anatomy|
One of the features of low carbohydrate diets that makes them popular is the rapid weight loss that is experienced by people on the diets. This weight loss occurs for several reasons. First, the body is forced to use carbohydrates and proteins for ready energy sources and the water that is bound to the carbohydrates and proteins in the body is lost as they are used as energy. Normally, about 4 grams of water is bound to each gram of carbohydrate in the body, so this weight loss can be significant. Unfortunately, it is as quickly regained when a normal carbohydrate intake is resumed. Another reason for the weight loss is that the body forms ketone bodies from some of the fat that is consumed. These ketone bodies are acidic and their excretion in the urine forces the body to excrete minerals to buffer the acids and to increase the amount of water that is lost to dilute the acids being excreted. This not only increases urination, but also increases thirst. Weight loss may also occur because calories are restricted--either voluntarily because of the monotony of the diet or involuntarily because ketone bodies are also appetite suppressants. A recent report from the USDA indicates that the main factor making diets effective is that calories are restricted--regardless of the source of those calories. However, the report concludes that the most effective diets for the long-term are those that allow for eating a healthy balance of foods form all food groups. You may find more information about the USDA report at the new web site www.nutrition.gov. Other information for this answer was derived from "Taking the Fear Out of Eating--A Nutritionists' Guide to Sensible Food Choices" by C. R. Gallagher and J.R. Allred and "Diet and Health--Implications for Reducing Chronic Disease Risk" by the National Research Council.
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