"Atkins is a high-protein, low-carbohydrate diet promising quick weight loss (up to 15 pounds) in the first two weeks. This quick weight loss claim is based on the idea that eating carbohydrates increases insulin hormone levels, thus increasing fat storage, hunger, and weight gain. It also assumes restricting carbohydrates will cause your body to use stored fat for energy instead of sugar from carbohydrate intake. There are four phases to the plan, the first of which severely restricts carbohydrates to just 20 grams per day and allows high intake of protein and fat.

Carbohydrates don't make you fat. Eating fat makes it easy to store fat. And eating too many calories from any source can cause weight gain. The rapid weight loss that occurs in phase one of Atkins is due to water loss. And the continuing weight loss is mainly due to muscle loss since your body must burn protein for energy from the lack of carbohydrate fuel.

Why doesn't your body burn fat instead? Fat-burning actually requires a minimum amount of carbohydrates (roughly 100-120 grams) per day. Any amount less than this means more muscle burning that fat burning.

Most of us add fat to our carbohydrate foods, which increases the calorie content. What do you put on baked potato? Butter, sour cream, cheese.. it's usually these toppings that load up our calories. A plain baked potato (about 5 oz) only has 110 calories and zero grams of fat, whereas a 'loaded' baked potato may have up to 400 calories and 15 grams of fat.

High-protein diets can cause bone-mineral losses (leaching calcium from the bones) and tend to be high in saturated fat and cholesterol, increasing the risk of heart disease. The nitrogen build-up in the blood from excess protein makes your body excrete more water to rid the waste, causing weight loss from water loss. This water loss often causes headaches, bad breath, and sometimes nausea. This diet is potentially unhealthy and would be very difficult to follow for the long-term.

--Cristina Caro, MBA, RD, LD
Licensed Nutrition Specialist
Program Coordinator, Healthy Lifestyles
Children's Healthcare of Atlanta