In a major study published in the February 26, 2009, issue of the New England Journal of Medicine, it was announced that all diets regardless of their composition have the same effect on long-term weight loss. At least that is what the media are saying. Unfortunately, the media rarely read the actual articles, and if they did, they would come to a very different conclusion.
Eight hundred obese individuals were put on four different diets, the two extremes being a low-fat, high-carbohydrate diet (20 percent fat and 65 percent carbohydrate) and a high-fat, high-protein diet (40 percent fat and 25 percent protein). I think it should be noted that none of the diets studied was the Zone Diet.
If you look at the all the data, there appeared to be no change in long-term weight loss among any of these diets. Upon closer inspection; however, there was a tremendous regression to the mean. This means that people on the low-fat diet started eating more fat, and people in the high-protein diet started eating less protein. All of this occurred in spite of intensive personal and group counseling for the two-year period of the study.
At the end of two years, when researchers asked what people were actually eating, it turns out that only 20 percent of the people in the higher-protein groups were still consuming 25 percent protein. Those who did were losing a lot more weight than those whose protein intake had dropped to 15 percent (the average protein amount). In fact, these changes had high statistical significance (p < 0.001). Interestingly, the 20 percent of the people in the low-fat, high-carbohydrate group who were consuming the most fat had gained significant weight at the end of two years compared to those who maintained a low-fat content. This result was also statistically significant (p<0.001). These were the only two results that were significant in the whole study and never mentioned by the authors of the article or the media (the data can be found in Figure 4 of the article).
What this study really indicates is: If you are eating a calorie-restricted, high-carbohydrate diet (i.e. the low-fat diet) and start to let small amounts of dietary fat creep into your diet, you are going to gain weight because the high insulin levels induced by the carbohydrate content of such a diet will drive extra fat into the fat cells. If you are eating a calorie-restricted, higher-protein-content diet and can maintain the protein level at greater than 25 percent of total calories, you will be losing a lot of weight because the carbohydrate levels are maintained at moderate levels and thus are not increasing insulin levels. That’s why the Zone Diet recommends 30 percent protein and no more than 40 percent carbohydrates -- you lose weight in the long-term by keeping insulin levels under control. Rather than trying to explain the only statistically relevant data of the study, the authors chose to say that dieters require more personal counseling. In the accompanying editorial comment, the author stated that maybe the only way to treat obesity in the future is by large-scale gastric bypass surgery.
Here is an even more radical thought. How about having people follow a strict Zone Diet with 30 percent protein and helping them maintain that protein level in the long term by the selective use of appropriately balanced snacks and meal replacements with the same macronutrient composition as the overall Zone Diet (30 percent protein, 40 percent low glycemic-load carbohydrates and 30 percent monounsaturated fat)? It’s a lot cheaper than gastric bypass surgery and a lot safer. This is the approach used by Manuel Uribe, once the fattest man in the world, to lose more than 500 pounds in three years. If it worked for Manuel, it should work for any dieter looking for long-term weight loss.