The panel often had inadequate or no data with which to answer the questions
about voluntary weight loss and control methods. Because voluntary weight loss
has important health implications and because Americans frequently attempt it,
an appropriate scientific base must be developed to maximize the chance for all
Americans to achieve a healthy weight.
Evidence suggests that the causes of overweight and obesity are
multifactorial. Thus, an appropriate research base must span the entire spectrum
of health research from genetic, biochemical, physiologic, and neurophysiologic
to individual, community, and population investigations. Research is needed
within and across these areas; the biomedical perspective should be incorporated
into clinical trials and population studies.
Obesity in humans has a substantial genetic basis. Numerous animal models of
obesity are attributable to defects in as yet unidentified genes. Molecular
genetic technology now makes identifying such genes possible in both animals and
humans. Characterization of the function of the gene products should facilitate
understanding of the biochemical, physiologic, and neural basis for regulation
of body weight and body fat, the resting metabolic rate, and metabolic
efficiency. Interactions between genetic makeup and environment or environment
alone during early childhood may influence the development of obesity.
Understanding basic mechanisms elucidated by gene analysis also may provide
important new insights into environmentally induced weight gain.
Physiologic research is helping define weight loss mechanisms that may be
useful in therapy. Mechanisms identified include suppressing appetite,
inhibiting gastric emptying, blocking carbohydrate or lipid digestion,
stimulating lipid oxidation, and increasing thermogenesis. These mechanisms
should be explored with pharmacotherapeutic research. Further efforts should be
made to identify other mechanisms. Elucidating the physiologic basis for body
fat distribution is important because of its relation to health.
The paucity of well-designed, long-term clinical trials evaluating various
methods for voluntary weight loss is disturbing. Particularly lacking are data
on minority populations and persons who are mildly to moderately overweight.
Long-term clinical trials will provide the most convincing evidence about the
longer term health effects of weight loss. Methods to improve compliance with
weight loss regimens and methods for long-term maintenance of weight control
should receive investigative priority. More must be known about the relationship
of binge-eating, dieting, and weight loss. Commercial weight loss programs
should routinely compile data on participant characteristics, attrition rates,
degree and duration of weight loss, and adverse effects for all participants.
Because several observational studies found weight loss was associated with
increased mortality, further analysis of existing data sets and survival studies
of persons losing weight voluntarily are urgently needed. Better studies are
needed to clarify long-term psychological effects of voluntary weight loss.
Physical and psychological outcomes of weight cycling deserve additional
investigation.
Population studies are needed to determine better the range of healthy
weights by age, gender, and ethnicity. The effects of obesity in childhood,
obesity treatment and prevention in children, and long-term consequences of
childhood obesity are important research priorities.
Research on the prevention of obesity and unhealthy weight gain is an area of
critical need. Of special importance are prevention of unhealthy weight gain in
certain minority populations and prevention of unhealthy dieting among
adolescent women. Weight and voluntary weight loss practices are closely tied to
cultural and societal attitudes toward weight and body image. Interdisciplinary
research involving all types of behavioral scientists is necessary to develop
and evaluate prevention programs that encourage Americans to adopt healthy
eating habits and lifestyles that will affect lifelong control of weight.
Methods must be developed to deal effectively with such problems as an
unrealistically thin ideal among some women and an uncritical acceptance of
dangerous overweight in certain cultures.
One quarter to one third of Americans are overweight; many have tried a variety
of methods to lose weight, with limited success in retaining weight loss. In
controlled settings, diets, behavior modification, exercise, and drugs produce
short-term weight losses with reasonable safety. Unfortunately, most people who
achieve weight loss with any of these programs regain weight. For many
overweight persons, achieving and maintaining a healthy weight is a lifelong
challenge.
Successful
weight loss
programs improve control of noninsulin-dependent diabetes
mellitus and hypertension, reduces cardiovascular risk factors, and enhances
self-image. Long-term health effects are much less clear. Several epidemiologic
studies raise the possibility that weight loss is associated with increased
mortality. The relevance of these findings to voluntary weight loss programs is
not yet clear.
Survey evidence also confirms that many Americans who are not overweight,
particularly young women, are trying different
diet
plans to lose
weight. This practice may have
significant adverse physical and psychological health consequences.
Because of the importance of these issues, research on the biologic and
social influences on weight and weight control and the health consequences of
weight loss and dieting should assume a high priority on the nation's health
agenda.
