^*According to Walter C. Willett, only 3.1 percent of the Nurses’ Health Study population could be described as following a “low risk” diet and lifestyle, which he defines as follows: nonsmoker, body-mass index (BMI) below 25 (the threshold for overweight), thirty minutes of exercise a day, and a diet characterized by low intake of trans fat; high ratio of polyunsaturated to saturated fats; high whole-grain intake; two servings of fish a week; recommended daily allowance of folic acid and at least five grams of alcohol a day. Based on fourteen years of follow-up, Willett and his colleagues calculated that, had the entire cohort adopted these behaviors, 80 percent of coronary heart disease; 90 percent of type 2 diabetes, and more than 70 percent of colon cancer cases could have been avoided. This analysis suggests that the worst effects of the Western diet can be avoided or reversed without leaving civilization. Or, as Willett writes, “the potential for disease prevention by modest dietary and lifestyle changes that are readily compatible with life in the 21st century is enormous.” From Walter C. Willet, “The Pursuit of Optimal Diets: A Progress Report” in Jim Kaput, and Raymond L. Rodriguez, Nutritional Genomics: Discovering the Path to Personalized Nutrition (New York: John Wiley & Sons, 2006).