Desire to weigh less is stronger predictor of health than obesity

Feb 13 2008

In a study to examine the impact of desired body weight on the number of unhealthy days subjects report over one month, researchers at Columbia University Mailman School of Public Health found that the desire to weigh less was a more accurate predictor of physically and mentally unhealthy days, than body mass index (BMI).

In addition, the desire to lose weight was more predictive of unhealthy days among Whites than among African-Americans or Hispanics, and among women than among men. The paper, I Think Therefore I Am: Perceived Ideal Weight as a Determinant of Health, will be published in the March issue of the American Journal of Public Health.

After controlling for actual BMI and age, the researchers found that men who wished to lose 1 percent, 10 percent, and 20 percent of their body weight, respectively, reported 0.1, 0.9 and 2.7 more unhealthy days per month than those who were happy with their weight. Among women, the corresponding increase in numbers of reported unhealthy days was 0.1, 1.6 and 4.3. Persons who were happy with their weight experienced fewer physically unhealthy days (3.0 vs 3.7) and mentally unhealthy days (2.6 vs 3.6) compared with persons unhappy with their weight.

“Our data suggest that some of the obesity epidemic may be partially attributable to social constructs that surround ideal body types,” said Peter Muennig, MD, MPH, Mailman School of Public Health assistant professor of Health Policy and Management. “Younger persons, Whites, and women are disproportionately affected by negative body image concerns, and these groups unduly suffer from BMI-associated morbidity and mortality.”

Approximately 66% of the more than 150,000 U.S. adults studied wanted to lose weight, and about 26% were satisfied with their current weight. With respect to BMI, 41% of normal weight people, 20% of overweight people, and 5% of obese people were happy with their weight. Older persons were also more likely to feel positively about their weight than were younger persons. However, in all models, perceived difference was a stronger predictor than was BMI of mentally and physically unhealthy days.

The researchers emphasize that there is a large body of evidence suggesting that social stress adversely affects mental health as well as physical health. “Our findings confirmed that there was a positive relationship between a person's actual weight and his or her desired weight and health, be it physical or mental,” observed Dr. Muennig.

Obesity is one of the greatest public health threats. Over 7 million quality-adjusted life years are lost annually as a result of excess body weight in the United States alone. There is evidence that discrimination against heavy people is pervasive, occurring in social settings, the workplace, and the home. These processes are likely internalized, leading to a negative body image that also may serve as a source of chronic stress.

“The data add support to our hypothesis that the psychological stress that accompanies a negative body image explains some of the morbidity commonly associated with being obese. Our finding that the desire to lose weight was a much stronger predictor of unhealthy days than was BMI further suggests that perceived difference plays a greater role in generating disease,” said Dr. Muennig.