Monday Fitness Fun Fact

The Power of Protein

High-protein, low-carbohydrate diets are the hottest thing since sliced flank steak, and every food marketer in the known universe appears to want a piece of the protein pie.Body builders are snatching, grabbing, and gulping down protein shakes. Dieters are gobbling down protein bars (and shunning pasta) in hopes of quick weight loss.

It's easy to understand the excitement. Protein is an important component of every cell in the body. Hair and nails are mostly made of protein. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood.

Along with fat and carbohydrates, protein is a "macronutrient," meaning that the body needs relatively large amounts of it. Vitamins and minerals, which are needed in only small quantities, are called "micronutrients." But unlike fat and carbohydrates, the body does not store protein, and therefore has no reservoir to draw on when it needs a new supply.

There are the obvious concerns about a high protein diet. Carbohydrate foods shunned by some people on low-carb diets include fruits and vegetables, which are the best sources for vitamins, fiber, and antioxidants -- nutrients that help prevent disease. By contrast, animal foods that are high in protein are usually also high in saturated fats, whi*****rease the risk for heart disease, stroke, diabetes, and several types of cancer.

The (Short-Term) Case for High Protein Diets

While no one knows the effect of eating a high-protein diet over the long term, the diet appears to be safe and effective for up to six months.

Frank Hu, MD, PhD, assistant professor in the Department of Nutrition at Harvard University School of Public Health in Boston, asked a student to review published studies on high-protein diets and try to answer these four important questions:

• Do high protein diets increase fat burning in the body?

• Do they increase satiety (the sense of being "full" or "satisfied" after a meal)?

• Do they decrease subsequent energy (calorie) intake by the body?

• Do they lead to weight loss?

For the most part, says Hu, the answers are "yes." Protein can be converted by the body into glucose for energy, but it takes twice as much effort as converting carbohydrates or fats into glucose. The extra effort translates into fewer calories available, Hu said at a recent symposium on the science of obesityobesity.

When it comes to feeling full, the clinical studies consistently showed that high-protein diets increase satiety and decrease hunger compared with high-fat or high-carbohydrate diets. In addition, most, but not all of the studies reviewed showed that most people on high-protein diets took in about 10% less energy (roughly 200 calories) per day, which could account for at least some of the weight loss seen with this type of diet.

"There is some evidence that high-protein diets induce great fat loss," Hu told the symposium audience. On average, high-protein diets produced an average weight loss that was about 4.5 lbs greater than that achieved on other diets after six months.

"Most of the studies show results for up to six months, but after six months they begin to lose effectiveness, either because people do not adhere to this diet very well in the long term, or because they get used to this diet biologically," Hu tells WebMD. "So in the long term the high-protein diets tend to lose their ability to maintain the weight."

Choose Your Proteins Wisely

The type of protein you eat may play a role in successful weight loss and in your overall health.

Consumption of large quantities of processed meats such as hot dogs, sausages, and deli meats, have been linked to increased risk of type 2 diabetes, cardiovascular disease, and colorectal cancer, Hu says. You'll have a harder time maintaining weight loss if you eat these proteins often, and you may be damaging your body.

Hu and other nutrition experts recommend getting dietary proteins from the following sources:

• Fish: Fish offers heart-healthy omega-3 fatty acids and, in general, less fat than meat.

• Poultry: You can eliminate most of the saturated fat by removing the skin.

• Beans: Beans contain more protein than any other vegetable protein. Plus, they're loaded with fiber that helps you feel full for hours.

• Nuts: One ounce of almonds gives you 6 grams of protein, nearly as much protein as one ounce of broiled ribeye steak.

• Whole grains: A slice of whole wheat bread gives you 3 grams of protein, plus valuable fiber.

 "A lot of plant-based foods like soy and legumes can give you the same amount of protein as meats. I have nuts for breakfast every day, because they not only give you a lot of protein, but they're healthy sources of fat," Hu says.

So when you decide to cut carbs and boost protein, take Hu's advice: Don't lose sight of the big picture.