HIGH-PROTEIN DIETS

Extra protein isn’t just attractive to athletes, who want to maintain or increase muscle mass—people trying to lose weight often turn to high-protein, low-carbohydrate diets, which promote getting 30% to 50% of total calories from protein. The potent ability of dietary proteins to reduce hunger and extend the time until we feel hungry again (satiety) is likely the main reason why these diets often produce rapid weight loss. However, long-term studies of weight loss suggest high-protein diets may help take weight off at first, but over the long haul, studies show little difference between diets higher and lower in protein in maintaining weight loss.

Recall that the AMDR for protein is 10% to 35% of total calories; in healthy people, intakes towards the upper end of the range are not associated with any negative effects. What is likely more important is the source of the protein. For instance, some studies have connected diets that are high in animal proteins with an increased risk of kidney stones, and diets high in red and processed meats, in particular, are associated with an increased risk of diabetes, cancer, and heart disease. However, it is unlikely that the increased risk is due to the increased intake of protein per se, but rather the constituents of these meat products. Processed meats are high in sodium and other preservatives that may be the underlying cause of the increased risk of chronic disease, while red meats in general are high in unhealthy fats. In contrast to the apparent ill effects of consuming a large amount of red and processed meats, diets with higher intakes of fish are generally associated with a lower risk of these diseases.

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High-protein diets. Some high-protein diets don’t provide the variety of foods needed to adequately meet all nutritional needs.
MSPhotographic/Shutterstock

Replacing red and processed meats with fish and poultry is linked to reductions in the risk of diabetes, cancer, and heart disease, and even greater risk reductions are seen when the meat is replaced with beans, legumes, and nuts. Substituting with fish and poultry will reduce the intake of unhealthy fats, while substituting with nuts and beans will have the added benefits of providing excellent sources of dietary fiber, essential fatty acids, and phytochemicals.

High-protein diets are often rich in saturated fat and cholesterol (refer to Infographic 8.11), but low in fiber, phytochemicals, and certain vitamins and minerals, since people are eating fewer grains, vegetables, and fruits. As a result, the American Heart Association does not recommend high-protein diets, since the typical intake may put people at risk of cardiovascular problems. “Over a long period, eating a lot of protein can set you up for problems,” says Dr. Lamont.

But what seems like a big increase in protein intake for athletes may not actually be so high when it is evaluated in light of their overall calorie intake, says Robert Wolfe, PhD, of the University of Arkansas for Medical Sciences. Someone competing at sports typically eats a much larger amount of calories overall, not just from protein—so doubling their protein intake may simply keep pace with other components of their overall diet, he says. “That seems like a big increase in protein, but you have to realize that total energy expenditure has also at least doubled,” he says. And even though some protein sources are “beefed up” with saturated fat and other unhealthy components, not all are. If athletes need extra calories for their workouts, there are worse sources than protein, adds Wolfe. “You have to consider protein not just as an isolated nutrient, but as one of three macronutrients in the body,” says Wolfe. “If you don’t eat more protein when you exercise and burn more calories, then you’re eating more carbohydrates and possibly more fat.” But some athletes who want to boost protein intake to levels far above the RDA often rely on protein-packed powders, rather than protein-containing foods, which they mix into shakes or smoothies, or sprinkle over meals.

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A fortunate inheritance. Olympian Michael Phelps requires not only a healthy diet, and an extraordinary amount of hard work, but exceptional genes to excel in swimming.
Simon Bruty/Sports Illustrated/Getty Images

When Stuart Phillips, PhD, professor of kinesiology at McMaster University in Ontario, lectures to varsity-level athletes, he asks them: What factors do you believe most contribute to your performance? Sometimes, he’ll even draw a pyramid, and ask them to fill it in with the most important factors at the bottom, representing the largest influence. Most place training, nutrition, and supplements at the bottom of the pyramid. “You’re wrong,” he says. Then he draws another pyramid. In the largest portion at the bottom he writes “genetics”—your biology is a major determinant of your athletic ability. But that’s not the only one; the next level of the pyramid is training. Finally, in the portion that’s at the top, he writes “nutrition.” Maybe he’ll add a little dot to represent supplements. Learn more about dietary supplements in Chapter 12.

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Even Michael Phelps, who ingested almost unimaginable amounts of food—including protein—to prepare for the Beijing Olympics, moderated his diet for the next Olympic Games in London. There, he typically started the day with a bowl of oatmeal, a large omelet with ham and cheese, and fruit. Although he didn’t win as many medals that time around, his diet likely had little to do with it, says Wolfe, who spent part of the 1990s studying female members of the U.S. Olympic swimming team. He agrees that diet is only one part of what makes an athlete successful. Phelps “could probably change his diet pretty drastically and still been a darn good swimmer,” says Wolfe. “That wasn’t why he was an Olympic champion—it was just one component. And from my experience with Olympic athletes, probably not a large component.”

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