The Paleo Diet - Loren Cordain [38]
The good news is that what you choose to eat—protein, fats, or carbohydrates—can influence the progression of insulin resistance. Dr. Gerald Reaven’s research at Stanford University has shown that low-fat, high-carbohydrate foods hinder insulin metabolism. But high-protein diets are known to improve insulin metabolism. Dr. P. M. Piatti and colleagues at the University of Milan put twenty-five overweight women on one of two diets. The first contained 45 percent protein, 35 percent carbohydrates, and 20 percent fat. The second contained 60 percent carbohydrates, 20 percent protein, and 20 percent fat. After twenty-one days the women on the high-protein diet had significantly improved insulin metabolism, but those on the high-carbohydrate diet actually got worse.
With all these benefits, it seems obvious that lean protein should be the starting point for all weight-loss diets. Prior to 2002, only three clinical trials of high-protein diets had been conducted. All three investigations found high-protein diets to be excellent—far better than low-fat, high-carbohydrate diets—at promoting weight loss.
Dr. Arne Astrup’s nutritional research group at the Royal Veterinary and Agricultural University in Copenhagen, Denmark, studied weight loss in sixty-five people placed on either high-protein or high-carbohydrate, reduced-calorie diets. After six months, those in the high-protein group had lost an average of 19.6 pounds—and 35 percent of the participants in this group had lost more than 22 pounds. The people in the high-carbohydrate group, however, lost only an average of 11.2 pounds; only 9 percent of the people in this group lost 22 pounds.
Dr. Hwalla Baba and colleagues at the American University of Beirut demonstrated almost identical results when they put thirteen overweight men on high- and low-protein, reduced-calorie diets. After only a month the average weight loss for men on the high-protein diet was 18.3 pounds compared to only 13.2 pounds for the high-carbohydrate group.
Dr. Donald Layman, a professor of nutrition at the University of Illinois, studied twenty-four overweight women who for ten weeks were on 1,700-calorie-a-day diets. Half of the women followed the current USDA Food Pyramid guidelines recommending a diet of 55 percent carbohydrate, 15 percent protein (68 grams per day), and 30 percent fat. The other half had a diet of 40 percent carbohydrate, 30 percent protein (125 grams a day), and 30 percent fat. The average weight loss for both groups was about 16 pounds, but the high-protein group lost 12.3 pounds of body fat and just 1.7 pounds of muscle compared to 10.4 pounds of body fat and 3 pounds of muscle for the Food Pyramid group. Interestingly, the study also found that women on the higher-protein diet had higher levels of thyroid hormone, which indicates that they had a faster metabolic rate. The higher-protein diet also resulted in a noticeable drop in triglyceride levels and a slight increase in the good HDL cholesterol.
In the eight years since I wrote the first edition of this book, numerous human clinical trials have conclusively demonstrated the superiority of high-protein diets in producing weight loss and benefiting overall health.
What You Can Expect to Lose on the Paleo Diet
When you start the Paleo Diet, you’ll probably realize—perhaps with a shock—just how much of your diet has been built around cereal grains, legumes, dairy products, and processed foods. Even most vegetarians must eat large amounts of grains and legumes to make their plant-based diets work, because it