Many researchers believe that the recent increase in obesity is being driven by environmental factors rather than biological ones. The environmental factors of particular concern are sedentary lifestyle and increased energy consumption, according to LSU AgCenter nutritionist Dr. Heli Roy.
The food supply is more abundant now than ever. Roy says per-capita calories consumed increased 15 percent between 1970 and 1994. The consumption of added fats has increased significantly since 1970. Consumption of cheese, soft drinks, snack and fast foods has increased while the intake of milk has decreased.
People are eating out more, too. An estimated 46 percent of adults eat out on any given day, and 21 percent of American families use restaurants daily.
The reliance on fast food and convenience foods can result in more calories, fat and lower fiber intakes, studies suggest. Portion sizes have increased over the years. Sizes that used to be considered appropriate for adults are now sold as "child-size" portions. For example, soft drinks have increased from their original size of 6.5 fluid ounces to 20 or 32 fluid ounce bottles.
Hamburgers and french fries are anywhere from two to five sizes larger than the originals. Candy bars and salty snacks have increased in size as well, and cookies are now 700 percent larger than a USDA standard size.
Roy says larger portion sizes encourage increased consumption and increased energy intake. In fact, bigger portion sizes are used as tools to sell more products. Such strategies have distorted portion sizes, leading consumers to underestimate their total dietary intake.
Although leisure time has increased since 1965, physical activity has not. In addition to increased energy consumption in the last 30 years, the American lifestyle has become more sedentary. About a quarter of the population reports no physical activity at all, while more than 60 percent are physically under active. Roy notes that in Louisiana 83.9 percent of adults report being physically inactive.
Ninety-eight percent of all U.S. households own a television. Adults spend an average of two hours watching television daily, and children and adolescents watch more than three and half hours a day.
"Television not only reduces physical activity but also influences people’s eating habits through advertising," Roy says, pointing out that food and beverage manufacturers spend an average of $11 billion a year on advertising.
A lot of advertising is targeted toward children, totaling some 20,000 commercials a year. Children then request foods that they see most often on television. High sugar cereals are the most frequently marketed product to children.
Lengthy television viewing correlates with obesity. Those who watch more than two and a half hours a day or more than four hours a day are 1.8 to 4 times more likely to be overweight. Television viewing has been found to predict weight gain in women.
In housing, research shows that lack of facilities and safety are two critical barriers to physical activity. Better neighborhood design with good connectivity and mixed land design results in higher level of physical activity. Highly walkable neighborhoods report 70 minutes more physical activity than minimally walkable neighborhoods. That is about the amount of time the American College of Sports Medicine and the 2005 Dietary Guidelines recommend for physical activity.
Roy says another contributor to obesity is the increased stress and demand place on employees today. Stress affects eating habits negatively, and it leads to overproduction of hormones that promote weight gain. In particular, stress promotes intra-abdominal weight gain which has been shown to be a risk factor for heart disease and diabetes.
Roy’s suggestions for improvement include regulating advertising to children, prohibiting fast foods from schools, improving neighborhoods for walk ability and reducing portion sizes.
For information on related family and consumer topics, visit the FCS Web site at http://www.lsuagcenter.com/
Inst/Extension/Departments/fcs/. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.