Background
Related Amber Waves Articles
Association between dietary patterns and obesity
To help address growing public health concerns about rising
obesity rates, ERS research illuminates differences in dietary
patterns by social, demographic, and economic factors. For example,
a greater share of low-income men consumes excessive calories and
has Body Mass Indices (BMIs) in the obese range than do high-income
men. Among women, however, low incomes tend to be associated with
high BMIs but lower caloric intakes. Determining the underlying
causes of disparities between patterns of caloric intake and body
fat measures across sociodemographic groups may lead to a better
understanding of the causes of disparities in overweight and
obesity (see "Food Stamps and Obesity: Ironic Twist or Complex
Puzzle?" and "U.S. Per Capita Food Supply Trends: More
Calories, Refined Carbohydrates, and Fats ").
ERS has examined the association between fruit and vegetable
consumption and obesity and found a negative relationship between
fruit consumption and BMI. That is, people who eat more servings of
fruit each day have lower BMIs. In fact, healthy-weight children
and adults eat significantly more fruits than their overweight and
obese counterparts (See table below). Vegetable consumption,
however, showed no consistent correlation with BMI. Why is fruit
consumption a more accurate predictor of body weight status than
vegetable consumption? The answer may lie in the way many Americans
incorporate these foods into their diets.
BMI definitions and
classifications |
Body Mass Index (BMI) = Weight
(Kilograms)/Height2 (Meters) |
|
Healthy weight
|
Overweight
|
Obese
|
BMI (index points) |
18.5-25
|
25-30
|
>30
|
Corresponding weight (6' 0") |
137-185 lbs.
|
185-220 lbs.
|
>220 lbs.
|
Corresponding weight (5' 6") |
115-155 lbs.
|
155-185 lbs.
|
>185 lbs.
|
Causes of obesity--an economist's view
The prevalence of obesity and overweight has increased
dramatically in the United States since the mid-1970s. The
prevalence of overweight has tripled among children and
adolescents, and nearly two of three adult Americans are either
overweight or obese. Although high costs-in health, social, and
economic terms-are known to be associated with obesity, how the
U.S. population reached this point is less well understood. In most
cases, weight gain and obesity are the result of individual
choices. Examining the causes of the increase in obesity and
proposed interventions under an economist's lens may help identify
potential solutions to the obesity crisis.
An overview of leading health economics research on the causes
and consequences of rising obesity in the United States can shed
light on the issue (see The Economics of Obesity: A Report on the Workshop
Held at USDA's Economic Research Service"). This research shows
how the technological changes driving modern economic growth have
raised household incomes, reduced the price of food, and increased
the price of physical activity. The resulting increase in energy
consumption (food intake) and flattening of energy expenditure
(physical activity) has tilted the weight equation in favor of a
steady weight gain across all segments of U.S. society ("The Price is Right: Economics and the Rise in
Obesity").
Although the incidence of obesity has risen among all population
groups, not everyone is equally at risk of becoming overweight or
obese. Understanding weight differences is one way to find
solutions to obesity and its associated health costs. ERS research
found that weight differs among demographic subgroups, and
differences in specific behaviors, health awareness, and eating
patterns can be linked to weight outcomes. These results suggest
that income, household composition, and formal education help
explain variation in behaviors and attitudes that are significantly
associated with weight outcomes (The Role of Economics in Eating Choices and Weight
Outcomes).
Differences between adults' actual weight status and their
perceived weight status show which individuals are mistaken in
their self-perceptions. Women tend to make more accurate
self-assessments than men but they are also more likely to
overestimate their weight status-healthy-weight women are much more
likely to indicate they think they are overweight, while overweight
men are more likely to underestimate their weight status and think
they are healthy. Mistakes in self-assessments are associated with
demographic factors, socioeconomic status, and knowledge and
attitudes toward diet and health. Federal information programs
targeting obesity and overweight will be more likely to influence
diet and lifestyle choices if the programs issue distinct messages
to different subgroups.
ERS has also examined how dietary choices and attitudes toward
diet and health contribute to obesity and whether those factors
differ by gender (contact Biing-Hwan Lin for reprint). Findings
indicate that:
- Choices and attitudes do matter, and the choices males and
females make often have quite different effects on BMI.
- A male's belief or lack of belief that weight status is genetic
has no influence on BMI.
- Women who do not believe that their weight is predetermined
have lower BMI values than those who believe weight is genetically
determined.
Can policies reduce obesity rates?
Action to combat obesity and overweight considers the many
variables that influence diet and lifestyle choices. The wide range
of factors affecting food choices is compounded by the incredible
variety of foods and consumption opportunities available today.
Lifestyle choices about diet quality and exercise also affect food
choices. Because consumers are faced with nearly unlimited choice,
public policy targeting specific foods or lifestyle choices could
have surprising unintended consequences.
ERS has examined some of the potential intended and unintended
consequences of three widely discussed obesity policies-nutrition
labels in restaurants, taxes on snack foods, and restrictions on
food advertising to children-with a focus on the likely effect of
each program on producer and consumer incentives and on health
outcomes. An apparently straightforward policy proposal can have
surprising effects that would dampen the policy's success in
reducing overweight and obesity: mandatory nutrition information at
fast food restaurants could lead to reformulations or price
promotions that do not necessarily contribute to more healthful
diets; taxes on snack foods could lead some consumers to substitute
equally unhealthy foods for the taxed food; and restrictions on
food advertising could ultimately lead to lower prices for food
subject to the restrictions. (Obesity Policy and the Law of Unintended
Consequences).