Dietary Trends and Chronic Disease
Cardiovascular disease,16 certain forms of cancer,17 diabetes,18 hypertension,19 and obesity20 are strongly related to dietary choices.
Cardiovascular Disease and Hypertension
Cardiovascular disease and hypertension are much more common in populations whose diets emphasize meat, cheese, and other animal-derived food products, and less common among those whose diets emphasize plant-derived foods.
An estimated 70 percent of cases of colorectal and prostate cancer; and about 50 percent of breast, endometrial, pancreatic and gallbladder cancer cases are diet-related.
According to the National Cancer Institute, as much as 75 percent of all cancer deaths in the United States are caused by lifestyle factors, particularly smoking, dietary choices, and physical inactivity.21 According to some estimates, about one-third of cancer deaths are attributable to diet, overweight, and physical inactivity.22,23 Some cancers are especially influenced by dietary choices: An estimated 70 percent of cases of colorectal and prostate cancer and 50 percent of cases of breast, endometrial, pancreatic, and gallbladder cancers are diet-related.24
The risks of developing obesity and type 2 diabetes are both strongly related to eating habits. According to a 2009 study of 60,903 American adults, body mass index was highest (28.8 kg/m2) in meat-eaters and lowest in those who avoided all animal products (23.6 kg/m2). A body mass index below 25 kg/m2 is considered healthy, while a value of 25 kg/m2 or above is considered overweight25 (See Figure 1).
Body mass index and diabetes prevalence were highest in meat-eaters and lowest in those who avoided all animal products.
Figure 1. Body mass index and diabetes prevalence, related to dietary habits. From: Tonstad S, et al. Type of vegetarian diet, body weight and prevalence of type 2 diabetes. Diabetes Care. 2009;32:791-796.
Increase in Consumption of Unhealthful Foods
Increases in disease prevalence reflect dramatic changes in Americans’ food habits. The U.S. Department of Agriculture began keeping records of Americans’ food intake in 1909, based on annual food production, imports, and beginning stocks, subtracting exports, ending stocks, and nonfood uses.
Between 1909 and 2007, the average American’s meat intake increased from 124 pounds per year to more than 200 pounds per year. Cheese intake rose from less than 4 pounds to nearly 33 pounds per year. Intake of sweeteners and added oils rose as well.26 (See Figure 2.)
Federal agricultural policies influence both the price and availability of foods.
These trends are attributable in part to increasing disposable income and purchasing power, increases in the number of meals eaten in commercial settings, and advertising. However, federal agricultural support policies also influence both the price and availability of foods. Subsidies for feed grains used for meat, dairy products, or egg production, subsidies for dairy products and sugar, and commodity purchases that favor meat, cheese, and eggs have contributed to trends in American eating habits. Federal nutrition guidance also influences what is available in food assistance programs.
Figure 2. Trends in meat and cheese consumption as estimated by food availability.
From: Barnard ND. Trends in food availability, 1909-2007. Am J Clin Nutr. 2010;91(suppl):1530S-1536S.
Current trends in overweight and obesity are primarily attributable to increased food intake, rather than to reduced physical activity.27 Although some have blamed physical inactivity for children’s weight problems, changing dietary habits have played a much greater role. Practically speaking, it is difficult to increase daily exercise sufficiently to compensate for American’s markedly increased calorie intake. For example, a one-hour bicycle ride burns 240 calories and, in comparison, one small order of french fries—which are consumed in much less than an hour—contains nearly the same number of calories.28 A 2011 review of school-based interventions found that weight loss could be achieved by diet changes alone, while exercise without diet changes was not effective.