Web edition: July 14, 2005
What's the answer to the nation's growing epidemic of obesity? "Get people to eat less and exercise more" might be obviousbut that's easier said than done, say Allen M. Spiegel and Barbara M. Alving of the National Institutes of Health.
That's why the American Journal of Clinical Nutrition has published the pair's comments, along with those from a host of other researchers, as a thematic collection of 14 reports in the journal's current issue. The scientists not only discuss factors that appear to be contributing to the nation's girth, but also explore the potential roles of different sectors of the economy in helping people trim down.
More than 65 percent of U.S. adults are overweight, including 31 percent of the population who are outright obese. And weight isn't just an adult problem. The proportion of children who are overweight has tripled in the past 35 years, to some 16 percent of school-age children and teens, the new reports note. If some studies are to be believed, the percentage may be higher still among the youngest kids (see When It's No Longer Baby Fat).
"Obesity is one of the most daunting health challenges of the 21st century," assert George L. Blackburn and W. Allan Walker of Harvard Medical School. Health effects associated with excess weight include up to 400,000 early deaths each year in the United States, they note, and cost society almost $120 billion. As these staggering figures confirm, they say, obesity is no longer an issue of aesthetics but a national crisis.
Key to dealing with it, the reports argue, is better understanding of what triggers people to consistently eat more calories than they burn.
Science has been pointing to aspects of biology such as how our bodies respond hormonally to various foods, the amount of sleep we get (SN: 4/2/05, p. 216), and even the siren call of food advertising. Research has also been teasing out factors affecting how our brain and gut register hunger or satiety based on sensations, such as what we see (see Diet TipClose Your Eyes).
However, one of the least appreciated contributors to obesity may be the very cost of healthful foods, argues one of the new reports.
Sweeter and fattier foodsthose that tend to offer the most calories per unit weighttend to cost less money than do lean meats, fish, fresh vegetables, and fruit. As such, the healthier cuisine advocated by health-care groups can strain the purse strings of many families. Such dietary advice can even spark resistance among low-income people by representing an "elitist approach to public health," according to Adam Drewnowski of the University of Washington and Nicole Darmon of INSERM, France's National Institute for Health and Medical Research.
They conclude that the demography of obesity in the United States suggests that the problem "is a largely economic issue."
Drewnowski and Darmon charge that health-care groups and the government have been issuing antiobesity recommendations based on a flawed premise: that eating a healthy dietone that derives most of its calories from fruits, vegetables, lean meats, and whole grainswill be easy once people learn the value of such foods and can identify them in the marketplace as a result of education and good labeling. In fact, the scientists observe, discussions of how people might eat healthier have largely ignored the extra costs that people probably will incur.
The ingredients castigated by the health-care communitysugars and added fatsare precisely those that are least expensive. The commodity cost of refined sugar on world markets is less than 10 cents a pound, Drewnowski and Darmon note. Vegetable oils cost only about twice that. Few other foods can deliver so much energymeasured as caloriesfor so little money. Small wonder, then, that companies make heavy use of these ingredients in processed foods.
Moreover, evolution appears to have made people prize such energy-dense fare. The theory goes that for most of human history, food has been plentiful at occasional feasts interspersed in long periods of near-famine. People therefore evolved a tendency to load up on dense calories in fat times so they could survive lean ones. Now that energy-dense sugars and fats are plentiful and inexpensive, biology may be sabotaging our health by continuing to make these foods enticing, Drewnowski and Darmon observe.
People with little money may also find fattening, cheap foods too big a bargain to pass up. The researchers calculated the commodity costs of largely unhealthy foodssuch as sugar, refined oils, refined grains, and potatoesand compared them with prices for healthier alternatives, such as fish, dairy products, fruit, vegetables, and lean meats. Drewnowski and Darmon then plotted the caloric content per edible unit against its marketplace price for some 760 foods.
The resulting analysis and graphs show that the healthier foods tend to cost dramatically more than the unhealthy ones.
In an earlier study, Darmon and several of her colleagues in France investigated how energy density and food costs relate to what consumers in that country were typically eating, based on a survey of more than 800 adults. It showed that for each 100 grams (3.5 ounces) of fruits and vegetables consumed per day, the cost of an individual's diet increased some 0.20 to 0.30 Euroor about 25 to 35 cents. By contrast, each 100 grams of fats and sweets eaten per day lowered the cost of an individual's diet by about 0.4 (almost 50 cents).
Energy-dense foods aren't always inexpensive. Consider the sweet, creamy confections prepared by upscale bakeries and restaurants. Some pastries command $15 or more per serving. "In other words," Drewnowski and Darmon observe, "deliberately selecting an energy-dense diet need not lead to lower diet costs."
However, they used computer modeling to see how people typically would cut a food budget without unduly sacrificing a diet's palatability. Their analysis showed that as a family lowers the amount it spends for food each day, consumption of fruits and veggies fall and the intake of fats and cereals (such as wheat or corn) climbs. The bottom line is that "restricting food expenditures will inevitably lead to more energy-dense diets," say the researchers.
This suggests that consumers on a tight food budget will find it hard to eat what nutritionists define as a healthy diet "unless they are willing to . . . subsist on unpalatable foods." In fact, the researchers point out, such drastic changes are exactly what some antiobesity guidelines recommend: substituting liver, dry beans, and canned fish for flour, sugar, and oils. Such foods tend to score low on taste, variety, and convenience, Drewnowski and Darmon point out, arguing against the likelihood that people would willingly adopt such substitutions.
For all of these reasons and more, the researchers conclude that "stemming the obesity epidemic cannot be separated from stemming the tide of poverty."
While acknowledging socioeconomic links to obesity, Spiegel and Alving point out that there are also many other factors that foster overeating and under-exercising. The two scientists cochair a 2-year-old NIH task force on obesity research.
The panel's goal, they say, is to find better weight-control interventions, better strategies for understanding obesity, better treatments for already overweight people at exaggerated risk for health problems, and more effective education for health-care professionals and the public.
Currently, they say, NIH is planning coordinated research across its institutes and grant-making committees to identify obesity risk factors, such as certain genes or infections (see Infectious Obesity). The institutes will also probe biological pathways that help regulate not only appetite but also the body's useversus storageof fat. These lines of research might eventually pay off by identifying new ways to help vulnerable individuals control what and how much they eat.
The institutes will also be looking deeper into how obesity can harm the body. Planned lines of inquiry include probes into the tie between obesity and diabetes (SN: 1/20/01, p. 36), between fat-cell proliferation and inflammation (SN: 2/28/04, p. 139: Available to subscribers at http://www.sciencenews.org/articles/20040228/bob9.asp), and between hormones and diet (see A New Shot at Fighting Obesity).
Among the new American Journal of Clinical Nutrition reports, one by researchers at the University of Pennsylvania describes a need for more research on typical eating and dieting behaviors at home, in restaurants, and at work. Other papers discuss the need for new and healthier food products, more-effective food labeling, and more exercise.
What these papers reinforce is that the obesity problem is too complex to be solved by such well-intentioned dietary advice as "eat less and exercise more." But the new data also indicate that the cost of not solving the problem, promptly, will be high in terms of both the nation's physical and financial health.
Barbara M. Alving
National Heart, Lung, and Blood Institute
Building 31, Room 5A52
31 Center Drive MSC 2486
Bethesda, MD 20892
George L. Blackburn
Beth Israel Deaconess Medical Center
Center for the Study of Nutrition Medicine
330 Brookline Avenue
Boston, MA 02215
National Institute For Health And Medical Research - INSERM
101, rue de Tolbiac
75654 Paris Cedex 13
Center for Public Health Nutrition
University of Washington
305 Raitt Hall, Box 353410
Seattle, WA 98195
Allen M. Spiegel
National Institute of Diabetes and Digestive and Kidney Diseases
National Institutes of Health
31 Center Drive
Bethesda, MD 20892
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