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perjantai 25. syyskuuta 2009

Weight-Loss Maintenance Success May Be Related to Brain’s Response to Seeing Food

Background There is overwhelming agreement that the recent increase in the prevalence of obesity is alarming, and efforts to prevent unhealthy weight gain across the lifespan are widespread. Whereas these initiatives are aimed mainly at prevention, it is also crucial to understand how overweight people can most effectively lose their excess weight and then keep it off. To understand lifestyle and biological factors associated with individuals who have succeeded in maintaining weight loss after dieting, the National Weight Control Registry has, since 1993, been tracking persons who have maintained a weight loss of 30 lb for 1 y. In a study led by Jeanne McCaffery from Brown Medical School and described in the October 2009 issue of The American Journal of Clinical Nutrition, data from this registry were used to investigate whether the brains of individuals who are able to maintain successful long-term weight loss respond differently to food pictures than do those of their obese counterparts. An accompanying editorial by Macdonald provides additional insight.

Study Design These investigators studied 3 groups of weight-stable individuals: normal weight (NW; n = 18) with body mass index (BMI; in kg/m2) between 18.5 and 24.9; obese (n = 16; BMI 30); and National Weight Control Registry participants with successful weight-loss (SWL) maintenance of 30 lb for 3 y (n = 17). After a 4-h fast, participants were shown a series of pictures that included low-energy foods (eg, salads), high-energy foods (eg, cheeseburgers), and nonfood objects (eg, shrubs). Neuroimaging was conducted using a magnetic resonance imaging scanner to document brain responses to each image.

Results As hypothesized, SWLs responded somewhat differently to these pictures than did obese and NW individuals. Specifically, SWLs showed greater activation in the left superior frontal and right middle temporal regions than did NW and obese controls. These changes are generally thought to be related to greater inhibitory control in the SWLs, which might result in greater ability to resist overeating. The results also supported the possibility that SWLs might experience greater visual attention to food images than do their obese and NW counterparts.

Conclusions The authors concluded that individuals who are especially successful in keeping weight off after it is lost may be able to do so, in part, because they experience greater inhibitory control and greater visual attention to food cues. Macdonald lauds this study for providing interesting data but cautions that it does not prove whether these differences are inherent within an individual or subject to change. He urges further longitudinal studies following obese individuals before, during, and after weight loss.

Lähde: AJCN Research Highlights October 2009

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