There's been so much press about protein lately that you'd think it was just invented. Our body-conscious society remains fixated by the stuff that can make Jennifer Aniston so skinny and yet bodybuilders so huge. To unravel the power of protein, the first installment of the Protein Primer will focus on the (fat) burning question: Do protein diets work?

 

Diets like The Zone and Atkins are not only high-protein (heavy on the meat, chicken, fish, eggs and dairy products) but also low-carbohydrate, which means a very limited intake of foods including bread, pasta, fruits and vegetables like potatoes and corn. The idea is to cut off the body's carbohydrate energy supply and force it to burn fat for its fuel.

 

The easiest way for the body to obtain its main fuel, glucose (aka blood sugar), is from carbohydrates; glucose is less easy to get from protein and rather difficult to get from fat. "If carbohydrates are not made available to the body for several days," explains the Mount Sinai School of Medicine in its reference book Total Nutrition, "the body attempts to conserve essential protein by producing an alternative fuel source from the partial burning of fatty acids."

 

That's when the weight loss begins.

 

"However, this initial weight loss [on the protein diet] is not fat, but water," states Mount Sinai, "caused by the kidney's attempts to rid the body of the excess [fatty acids called] ketones [that build up in the blood as the breakdown of fat continues] and of the by- products of the breakdown of protein."

 

Think of the weight loss as a wet sponge that has been wrung out, says nutritionist Tracy Stopler Kasdan, M.S., R.D. "One gram of carbohydrate stores 3 grams of water," she explains, "and an individual following a low carbohydrate diet is storing less water which will cause weight loss." That is one reason why, says Kleiner, that such a diet "works." The other reason is that it does actually force the body to burn fat as fuel for lack of carbohydrates.

 

But is this method safe? "A ketogenic diet [one that produces ketones], when monitored by a physician, need not necessarily be harmful," says Kleiner. "Unmonitored, however, it can be seriously detrimental to your health. Any diet that eliminates food groups, particularly fruits, vegetables and grains—clearly the backbone of the disease-prevention diet—cannot be healthy for the long term."

 

Therefore, if your goal is to lose five pounds before the office holiday party two weeks from now, the protein diet approach will work, says Kleiner. But if you want to take off weight and keep it off forever, she warns, "this will just be another diet that you go on to go off." And once you go back to eating carbohydrates, says Stopler Kasdan, "expect the water-weight gain to start." This shouldn't send you off the deep end, just make it your signal to return to healthy eating habits and a more balanced diet.