Prevalence and trends in obesity among US adults, 1999-2000

The Supersizing of America: Portion Size and the Obesity Epidemic

Although we are just beginning to understand how environmental factors such as portion size affect eating behavior, the available data suggest that large portions of energy-dense foods are contributing to the obesity epidemic. Several possible strategies for adjusting portions to bring intake back in line with energy requirements are discussed. The continuing rise in the rates of obesity calls for urgent action.

The kidney, hypertension, and obesity

This paper provides a personal perspective of the role of abnormal renal-pressure natriuresis in the pathogenesis of hypertension. Direct support for a major role of renal-pressure natriuresis in long-term control of arterial pressure and sodium balance comes from studies demonstrating that (1) pressure natriuresis is impaired in all forms of chronic hypertension and (2) prevention of pressure natriuresis from operating, by servo-control of renal perfusion pressure, also prevents the maintenance of sodium balance hypertension. Although the precise mechanisms of impaired pressure natriuresis in essential hypertension have remained elusive, recent evidence suggests that obesity and overweight may play a major role. Obesity increases renal sodium reabsorption and impairs pressure natriuresis by activation of the renin-angiotensin and sympathetic nervous systems and by altered intrarenal physical forces. Chronic obesity also causes marked structural changes in the kidneys that eventually lead to a loss of nephron function, further increases in arterial pressure, and severe renal injury in some cases. Although there are many unanswered questions about the mechanisms of obesity hypertension and renal disease, this is one of the most promising areas for future research, especially in view of the growing, worldwide "epidemic" of obesity.

A war on obesity, not the obese

In their efforts to lose weight, obese individuals may be fighting a powerful set of evolutionary forces honed in an environment drastically different from that of today.

Treatment and prevention of obesity: what works, what doesn't work, and what might work

We provide a very broad conceptual overview of some of the issues involved in the treatment and prevention of obesity. Data suggest that clinicians have some ability to promote positive changes with obesity treatment. The environment, though important in influencing one's degree of adiposity, has largely transient effects that do not tend to carry over from one time to substantially later times. In contrast, the genetic influences on body mass index at any one time do tend to carry over to later times. This information influences the types of approaches that are and are not likely to be successful in terms of preventing obesity or reducing obesity on a population level. A second issue concerns the composition of weight lost. Conditional on fat loss, weight loss has been associated with an increased mortality rate (MR) whereas, conditional upon weight loss, fat loss has been associated with a decreased MR. This suggests that we should seek treatments that maximize the proportion of weight lost as fat. Third, the efficacy of current treatments is far below patients' expectations and desires. We need both to increase the efficacy of our treatments dramatically and help patients adjust their expectations so that they can take satisfaction in smaller weight losses. Perhaps, with continued efforts at enhancing treatments, we will see incremental advances in the treatment and prevention of obesity.

Expanding portion sizes in the US marketplace: implications for nutrition counseling

The greater energy content of larger food portions could be contributing to the increasing prevalence of overweight. Prevention guidelines recommend "sensible" portion sizes but do not define them. The US Department of Agriculture (USDA) defines standard serving sizes for dietary guidance, and the Food and Drug Administration (FDA) defines standard servings for food labels. To use these standards in counseling, nutritionists must know the sizes of portions available in the marketplace. We determined marketplace portion sizes, identified changes in these sizes with time, and compared current marketplace portions with federal standards. Most marketplace portions exceed standard serving sizes by at least a factor of 2 and sometimes 8-fold. Portions have increased over time; those offered by fast-food chains, for example, often are 2 to 5 times larger than the original size. The discrepancy between marketplace portions and standard servings suggests the need for greater emphasis on the relationship of portion size to energy intake as a factor in weight maintenance.

Genetics of obesity: more complicated than initially thought

During the past several decades, there has been an explosion in the prevalence of obesity. Since our genes have not changed appreciably during that time, it stands to reason that the present epidemic is caused by our pervasive obesigenic environment, in which excess caloric intake and decreased physical activity conspire with one another. Despite an obesigenic environment, humans have great variability in their susceptibility to obesity, which is determined in large part by genetics. Current evidence suggests that genetic susceptibility to human obesity is the result of multiple genes, each with a modest effect, that inter-act with each other and with environmental provocations. Elucidation of obesity susceptibility genes through genome-wide and candidate gene approaches provides great promise in ultimately determining the genetic underpinnings of obesity. Further research will translate these new insights on the pathophysiological basis of obesity into new medications and diagnostic tests.

Patterns and trends in food portion sizes, 1977-1998

CONTEXT

While general consensus holds that food portion sizes are increasing, no empirical data have documented actual increases.

OBJECTIVE

To determine trends in food portion sizes consumed in the United States, by eating location and food source.

DESIGN, SETTING, AND PARTICIPANTS

Nationally representative data from the Nationwide Food Consumption Survey (1977-1978) and the Continuing Survey of Food Intake by Individuals (1989-1991, 1994-1996, and 1998). The sample consists of 63 380 individuals aged 2 years and older.

MAIN OUTCOME MEASURE

For each survey year, average portion size consumed from specific food items (salty snacks, desserts, soft drinks, fruit drinks, french fries, hamburgers, cheeseburgers, pizza, and Mexican food) by eating location (home, restaurant, or fast food).

RESULTS

Portion sizes vary by food source, with the largest portions consumed at fast food establishments and the smallest at other restaurants. Between 1977 and 1996, food portion sizes increased both inside and outside the home for all categories except pizza. The energy intake and portion size of salty snacks increased by 93 kcal (from 1.0 to 1.6 oz [28.4 to 45.4 g]), soft drinks by 49 kcal (13.1 to 19.9 fl oz [387.4 to 588.4 mL]), hamburgers by 97 kcal (5.7 to 7.0 oz [161.6 to 198.4 g]), french fries by 68 kcal (3.1 to 3.6 oz [87.9 to 102.1 g]), and Mexican food by 133 kcal (6.3 to 8.0 oz [178.6 to 226.8 g]).

CONCLUSION

Portion sizes and energy intake for specific food types have increased markedly with greatest increases for food consumed at fast food establishments and in the home.

Effect of exercise on total and intra-abdominal body fat in postmenopausal women: a randomized controlled trial

CONTEXT

The increasing prevalence of obesity is a major public health concern. Physical activity may promote weight and body fat loss.

OBJECTIVE

To examine the effects of exercise on total and intra-abdominal body fat overall and by level of exercise.

DESIGN

Randomized controlled trial conducted from 1997 to 2001.

SETTING AND PARTICIPANTS

A total of 173 sedentary, overweight (body mass index > or =24.0 and >33% body fat), postmenopausal women aged 50 to 75 years who were living in the Seattle, Wash, area.

INTERVENTION

Participants were randomly assigned to an intervention consisting of exercise facility and home-based moderate-intensity exercise (n = 87) or a stretching control group (n = 86).

MAIN OUTCOME MEASURE

Changes in body weight and waist and hip circumferences at 3 and 12 months; total body, intra-abdominal, and subcutaneous abdominal fat at 12 months.

RESULTS

Twelve-month data were available for 168 women. Women in the exercise group participated in moderate-intensity sports/recreational activity for a mean (SD) of 3.5 (1.2) d/wk for 176 (91) min/wk. Walking was the most frequently reported activity. Exercisers showed statistically significant differences from controls in baseline to 12-month changes in body weight (-1.4 kg; 95% confidence interval [CI], -2.5 to -0.3 kg), total body fat (-1.0%; 95% CI, -1.6% to -0.4%), intra-abdominal fat (-8.6 g/cm2; 95% CI, -17.8 to 0.9 g/cm2), and subcutaneous abdominal fat (-28.8 g/cm2); 95% CI, -47.5 to -10.0 g/cm2). A significant dose response for greater body fat loss was observed with increasing duration of exercise.

CONCLUSIONS

Regular exercise such as brisk walking results in reduced body weight and body fat among overweight and obese postmenopausal women.

Years of life lost due to obesity

CONTEXT

Public health officials and organizations have disseminated health messages regarding the dangers of obesity, but these have not produced the desired effect.

OBJECTIVE

To estimate the expected number of years of life lost (YLL) due to overweight and obesity across the life span of an adult.

DESIGN, SETTING, AND SUBJECTS

Data from the (1) US Life Tables (1999); (2) Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994); and (3) First National Health and Nutrition Epidemiologic Follow-up Study (NHANES I and II; 1971-1992) and NHANES II Mortality Study (1976-1992) were used to derive YLL estimates for adults aged 18 to 85 years. Body mass index (BMI) integer-defined categories were used (ie, <17; 17 to <18; 18 to <19; 20 to <21; 21 to 45; or > or =45). A BMI of 24 was used as the reference category.

MAIN OUTCOME MEASURE

The difference between the number of years of life expected if an individual were obese vs not obese, which was designated YLL.

RESULTS

Marked race and sex differences were observed in estimated YLL. Among whites, a J- or U-shaped association was found between overweight or obesity and YLL. The optimal BMI (associated with the least YLL or greatest longevity) is approximately 23 to 25 for whites and 23 to 30 for blacks. For any given degree of overweight, younger adults generally had greater YLL than did older adults. The maximum YLL for white men aged 20 to 30 years with a severe level of obesity (BMI >45) is 13 and is 8 for white women. For men, this could represent a 22% reduction in expected remaining life span. Among black men and black women older than 60 years, overweight and moderate obesity were generally not associated with an increased YLL and only severe obesity resulted in YLL. However, blacks at younger ages with severe levels of obesity had a maximum YLL of 20 for men and 5 for women.

CONCLUSION

Obesity appears to lessen life expectancy markedly, especially among younger adults.

Trends in incidence rates for obesity-associated cancers in the US

The purpose of this study was to assess the possible impact of rising prevalence of obesity in US adults (since the late 1970s) on incidence rates (1973-1999) for cancers strongly associated with obesity, and to estimate the number of incident cancers (in 2002) potentially attributable to obesity. Data from a group of high-quality population-based cancer registries, regarded as generally representative of the unknown cancer rates in the entire US, were used to obtain average annual age-standardized incidence rates (ASIRs) per 100,000 from 1973 to 1975 through 1997-1999 for selected obesity-related cancers. Temporal increases in ASIRs were evident during the entire period for kidney and adenocarcinomas of the esophagus and gastric cardia, while during the 1990's the decline in ASIRs for adenocarcinoma of the uterine corpus was reversed and the ASIRs for breast cancer continued to increase for age 50+ years, suggesting a potential impact of rising obesity prevalence rates. An estimated 41,383 new cancers (about 3.2% of all cancers) diagnosed in the US in 2002 may be potentially attributable to obesity. Further analytic epidemiologic studies are needed to assess the risks of other cancers in relation to both obesity and body fat distribution.

Advances in the Understanding and Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a well recognised form of chronic liver disease that has recently gained greater recognition. Originally described in the late 1950s, NAFLD is currently considered the leading cause of abnormal liver enzyme levels in the US, closely paralleling the increase in obesity and diabetes mellitus. NAFLD has a worldwide distribution, affecting both adults and children, and typically is seen in association with obesity, diabetes, hypertension and hypertriglyceridaemia. Most patients are asymptomatic and usually present with mild elevations in aminotransferases. The natural history of NAFLD is not clearly defined but progression to cirrhosis and end-stage liver disease is well recognised in some patients. The accumulation of hepatic steatosis is thought to occur initially, primarily through hepatic and peripheral insulin resistance, which leads to altered glucose and free fatty acid metabolism. The progression from simple fatty liver to more severe forms of NAFLD (nonalcoholic steatohepatitis and cirrhosis) is much less clear but evidence suggests that oxidative stress may preferentially enhance proinflammatory cytokines, which leads to cellular adaptations and dysfunction followed by development of inflammation, necrosis and fibrosis. Therapeutic modalities remain limited and are largely focused on correcting the underlying insulin resistance or reducing oxidative stress. However, at the present time, there are several limitations to the current potential therapies, mainly because of the lack of large-scale, prospective, randomised studies, as well as clearly defined histological endpoints. Ultimately, the future for potential therapeutic modalities to treat this disease are quite promising, but further research is needed to clearly demonstrate which therapy or therapies will be effective at eliminating fatty liver disease and its potential complications.

Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001

CONTEXT

Obesity and diabetes are increasing in the United States.

OBJECTIVE

To estimate the prevalence of obesity and diabetes among US adults in 2001.

DESIGN, SETTING, AND PARTICIPANTS

Random-digit telephone survey of 195 005 adults aged 18 years or older residing in all states participating in the Behavioral Risk Factor Surveillance System in 2001.

MAIN OUTCOME MEASURES

Body mass index, based on self-reported weight and height and self-reported diabetes.

RESULTS

In 2001 the prevalence of obesity (BMI > or =30) was 20.9% vs 19.8% in 2000, an increase of 5.6%. The prevalence of diabetes increased to 7.9% vs 7.3% in 2000, an increase of 8.2%. The prevalence of BMI of 40 or higher in 2001 was 2.3%. Overweight and obesity were significantly associated with diabetes, high blood pressure, high cholesterol, asthma, arthritis, and poor health status. Compared with adults with normal weight, adults with a BMI of 40 or higher had an odds ratio (OR) of 7.37 (95% confidence interval [CI], 6.39-8.50) for diagnosed diabetes, 6.38 (95% CI, 5.67-7.17) for high blood pressure, 1.88 (95% CI,1.67-2.13) for high cholesterol levels, 2.72 (95% CI, 2.38-3.12) for asthma, 4.41 (95% CI, 3.91-4.97) for arthritis, and 4.19 (95% CI, 3.68-4.76) for fair or poor health.

CONCLUSIONS

Increases in obesity and diabetes among US adults continue in both sexes, all ages, all races, all educational levels, and all smoking levels. Obesity is strongly associated with several major health risk factors.

Health promoting community design: a new paradigm to promote healthy and active communities

Richard Killingsworth explains that we have engineered routine forms of physical activity out of our daily lives, and that this is an important contributor to the obesity epidemic which claims at least 200,000 lives each year in the United States alone. A new field of study is emerging to address this problem, and the American Journal of Health Promotion has launched a new editorial section called "Health Promoting Community Design" to provide a forum to disseminate research in this new area.

Long-term pharmacotherapy for obesity and overweight

BACKGROUND

Worldwide prevalence rates of obesity and overweight are rising and safe and effective treatment strategies are urgently needed. A number of anti-obesity agents have been studied in short-term clinical trials, but long-term efficacy and safety need to be established.

OBJECTIVES

To assess/compare the effects and safety of approved anti-obesity medications in clinical trials of at least one-year duration.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Controlled Trials Register, the Current Science Meta-register of Controlled Trials, and reference lists of original studies and reviews were searched. Date of last search was December 2002. Drug manufacturers and two obesity experts were contacted in to detect unpublished trials. No language restrictions were imposed.

SELECTION CRITERIA

Double-blind, randomised controlled weight loss and weight maintenance trials of approved anti-obesity agents that 1) enrolled adult overweight or obese patients, 2) included a placebo control group or compared two or more anti-obesity drugs 3) used an intention-to-treat analysis, and 4) had a minimum follow-up period of one year. Abstracts and pseudo-randomised trials were not included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed all potentially relevant citations for inclusion and methodological quality. The primary outcome measure was weight loss.

MAIN RESULTS

Of the eight anti-obesity agents investigated, only orlistat and sibutramine trials met inclusion criteria. Eleven orlistat weight loss studies (four of which reported a second year weight maintenance phase) and five sibutramine studies (three weight loss and two weight maintenance trials) were included. Attrition rates averaged 33% during the weight loss phase of orlistat trials and 43% in sibutramine studies. All patients received lifestyle modification as a co-intervention. Compared to placebo, orlistat-treated patients lost 2.7 kg (95% CI: 2.3 kg to 3.1 kg) or 2.9% (95% CI: 2.3 % to 3.4%) more weight and patients on sibutramine experienced 4.3 kg (95% CI: 3.6 kg to 4.9 kg) or 4.6% (95% CI: 3.8% to 5.4%) greater weight loss. The number of patients achieving ten percent or greater weight loss was 12% (95% CI: 8% to 16%) higher with orlistat and 15% (95% CI: 4% to 27%) higher with sibutramine therapy. Weight loss maintenance results were similar. Orlistat caused gastrointestinal side effects and sibutramine was associated with small increases in blood pressure and pulse rate.

REVIEWER'S CONCLUSIONS

Studies evaluating the long-term efficacy of anti-obesity agents are limited to orlistat and sibutramine. Both drugs appear modestly effective in promoting weight loss; however, interpretation is limited by high attrition rates. Longer and more methodologically rigorous studies of anti-obesity drugs that are powered to examine endpoints such as mortality and cardiovascular morbidity are required to fully evaluate any potential benefit of such agents.

Outpatient management of obesity: a primary care perspective

An estimated 64% of the adult population in the United States is either overweight or obese. Because obesity affects such a large percentage of the population and carries with it numerous health risks, it is essential that physicians treat obesity and encourage healthy-weight maintenance within the primary care setting. Effective weight management will require providing the appropriate physical environment for the overweight or obese patient, properly evaluating the impact of a patient's weight on health, evaluating a patient's readiness to change, setting appropriate weight-loss goals, and providing information and help about how to modify dietary and physical activity patterns. Achieving and maintaining weight loss is more likely to be successful when there is a physician-patient partnership where the physician provides support and motivation for the patient's efforts to initiate and maintain a healthy body weight.