The State of Obesity and Obesity Research

Class II obesity (body mass index [BMI] >35) and class III obesity (BMI ≥40) is a prevalent condition that adversely affects health. According to the latest National Health and Nutrition Examination Survey (2007-2008), the prevalence of class II and III obesity was 14.3% of the US population 20 years or older.¹ Women have a higher prevalence (17.8%) than men (10.7%) and non-Hispanic blacks have a higher prevalence (21.9%) than non-Hispanic whites (13.6%), with non-Hispanic black women having the highest prevalence reported (27.9%). Even though the overall rates of increase for obesity (proportion of the population with BMI >30) may have slowed in the last decade,¹ the population distribution among men and women in the United States clearly indicates that class II and III obesity is a problem to be reckoned with, especially in women.

A health problem of this severity would be expected to spawn copious clinical investigation, but the state of medical research in class II and III obesity is limited primarily to reports of surgical intervention. In fact, pessimism is widespread regarding the benefit of nonsurgical therapies for class III obesity, even though only a small proportion of patients eligible for bariatric surgery procedures actually receive them. Even current guidelines that direct evidence-based treatment approaches in primary care settings contain the statement, “Extremely obese persons often do not benefit from the more conservative treatments for weight loss and weight maintenance.”²

In this issue of JAMA, Goodpaster and colleagues³ report the results of their clinical trial involving 2 approaches to lifestyle intervention in persons with BMI of 35 or greater—immediate or delayed introduction of moderate-intensity physical activity to a dietary restriction program. This study shows that patients with class II and III obesity can derive health benefits from lifestyle-change counseling targeted at diet and physical activity. The patients most in need (ie, those with more severe obesity) stand to benefit the most from weight loss. The participants in this study achieved substantial improvements in risk factors, especially waist circumference, visceral fat, blood pressure, liver enzymes, and liver fat content, with mean weight loss of 10.8% and 13.1% at 1 year.

Goodpaster et al³ tested approaches of immediate or delayed (for 6 months) recommendations for physical activity, and although there were small but statistically significant differences in weight loss at 6 months, there were no differences in weight loss at 12 months. Is the inference from this observation that it is acceptable to forgo physical activity during lifestyle change? On the contrary, physical activity added to dietary measures results in an incremental weight loss of 1 to 3 kg, and physical activity behaviors are cardinal to maintenance of weight loss.⁴ Furthermore, both treatment groups received physical activity recommendations, although after a 6-month delay in one group. The bottom line is that physical activity was an important component of both interventions.

The recommendation to engage in 60 minutes of moderate-intensity physical activity for 5 days per week (for a total of 300 minutes per week) is categorized as high activity by the 2008 Physical Activity Guidelines for Americans.⁵ This level of activity was chosen because studies have consistently shown that a large dose of physical activity is needed for substantial weight loss.⁴ However, as the study by Goodpaster et al³ demonstrates, the benefits of physical activity are not measured only by the amount of weight loss. Adults who participate in physical activity during weight loss have improvements in body composition, body fat loss, and waist circumference.⁶ Although more is better when it comes to exercise, high levels of moderate-intensity activity, such as brisk walking, should be incorporated into weight loss programs.

If the report by Goodpaster et al³ demonstrates the efficacy of lifestyle counseling in class II and III obesity, is it the state-of-the art to implement these approaches in primary care? The authors drew on their experience from participation in the Diabetes Prevention Program⁷ and Look AHEAD⁸ lifestyle intervention delivery. These programmatic approaches involve trained counselors and the provision of written guidelines for counselors and participants to direct therapy. However, the current state of third-party payer policies is that reimbursement for these programs is rare. Physicians should not be discouraged from implementing nonsurgical medical care approaches in this population, but payers need to rethink their policies. Programmatic lifestyle change approaches^{9 - 10} have demonstrated the health benefits of lifestyle interventions in special populations (such as overweight and obese patients with prediabetes or diabetes), but implementing such interventions is still not regularly reimbursed.

The report by Goodpaster et al³ also includes interesting observations regarding race/ethnicity, with differences in the amount of weight loss in African American compared with white persons. This finding also was observed in Look AHEAD¹¹ and other studies¹² that used a similar lifestyle intervention. Given the greater risk for severe obesity in African American persons, it is concerning that there is also a lesser chance for weight loss with lifestyle intervention in this population. What are the underlying mediators of these observations? Are there biological factors that impose greater risk and that also in some way mediate weight loss response? Do cultural factors play a role? These questions deserve further study, since the burden of disease is disproportionately borne by one group who derive less benefit from weight-loss interventions.

Severe obesity is a prevalent public health problem, disproportionately affecting women and minorities. There is still much to learn about the mechanisms underlying differing risk and treatment outcomes between populations. Optimal treatment approaches for class II and class III obesity are underexplored, while payment approaches for interventions known to work have yet to be adopted. Despite this state of affairs, there is reason for some optimism. There is much to examine in obesity research and many avenues to explore. Additional rigorous research, such as the clinical trial by Goodpaster et al,³ are needed to unravel the causes, identify prevention strategies, and develop the best treatments for obesity.