Research into what some have called an epidemic of overweight in America has, thus far, not shown a clear pattern of causation. In a study published in The American Journal of Clinical Nutrition, Harnack et al. of the University of Minnesota used a different perspective from previous national dietary surveys; instead they analyzed the quantities and types of foods and nutrients marketed in America over the past three decades. They found that the per capita availability of energy increased 15% between 1970 and 1994. Trends in purchasing and preparation of food also have changed in ways that may be contributing to overweight. Americans are eating more meals outside the home, relying more on convenience foods, and may be consuming larger food portions.
Combining government and commercial food industry sources, the researchers conducted computer-assisted searches of English-language publications to calculate per capita estimates of the availability of a number of foods items. Trends showed increases in the availability of fish and chicken, fresh and frozen fruits and vegetables, and low fat milk. Higher-fat cheeses showed a 325% increse. Also expanding were common ingredients of processed foods such as corn sweetener, flours and cereals, shortening and cooking oils. These increases could be attributed to the growth of fast food restaurants and other away-from-home eating establishments, where much of the food is prepared by deep fat frying.
The article points to dramatic changes in food purchasing and preparation in America. Of every dollar used to buy food, American households spent 20% to eat away from home in the 1970s, but by 1992 this proportion had increased to 38%. Fast food restaurants are currently growing at a rate of 7% annually. Supermarkets increasingly offer convenience foods and pre-made dinners in order to compete with the restaurant industry. Larger portion sizes, according to the authors, might also be contributing to the weight gain problem, though more research is needed. Restaurant menus collected and analyzed by the National Restaurant Association between 1988 and 1993 showed a 12% increase in offerings of more than one portion size, such as a "king size" steak.
As a whole, this ecological perspective parallels national dietary survey data in suggesting that energy intakes by Americans have been increasing over the past several decades, and that this increase is a contributor to the prevalence of overweight.
For the complete text of this manuscript please go to: http://www.faseb.org/ascn/temp/ajcn/1478-1484p-harnack11.pdf
Harnack, L J et al. Temporal trends in energy intake in the United States: an ecological perspective. Am J Clin Nut 2000;71:1478-1484
For more information please contact Dr.Lisa J. Harnack at harnack@epivax.epi.umn.edu
This media release is provided by The American Society for Clinical Nutrition, to provide current information on nutrition-related research. This information should not be construed as medical advice. If you have a medical concern, consult your doctor.
Journal
American Journal of Clinical Nutrition