CHICAGO (AP) -- An epilepsy drug combined with a reduced-calorie diet may result in significant weight loss for obese adults, according to one of several obesity studies in this week's Journal of the American Medical Association.

The epilepsy drug research was prompted by reports of unintentional weight loss in epilepsy patients using zonisamide to prevent seizures.

In the Duke University study, participants who took zonisamide daily for 16 weeks lost an average of nearly 13 pounds, compared with about 2 pounds in patients given dummy pills.

Both groups also ate 500 fewer calories daily in a diet monitored by a dietitian, and were encouraged to increase their activity levels. Patients were mostly women, aged 21 to 50, and weighed over 200 pounds on average.

The study was small -- just 60 patients -- and the results are preliminary, but they suggest the drug could be a promising addition to efforts to control the nation's obesity epidemic, according to a research team led by Duke's Dr. Kishore Gadde.

Some 30 percent of U.S. adults are obese and 60 percent are overweight.

The study was funded by Elan Biopharmaceuticals, makers of zonisamide, which is sold under the brand name Zonegran.

Also in Wednesday's JAMA:

• A Harvard University study of more than 50,000 women bolsters the link between sedentary lifestyles and obesity, finding a 23 percent increased risk of obesity and a 14 percent increased risk of diabetes for every two hours of television watched daily.

  By contrast, watching less than 10 hours of TV weekly and engaging in brisk walking at least half an hour daily reduced the obesity and diabetes risks by 30 percent and 43 percent respectively.

• The prescription diet drug Meridia helped adolescents lose weight when combined with behavior therapy, but also was linked with increases in pulse rate and blood pressure that have been found in adults.

  The research team led by Dr. Robert Berkowitz of the University of Pennsylvania said the drug should only be used on an experimental basis in adolescents and children "until more safety and efficacy data are available."

• A research review concluded that any success with low-carbohydrate regimens including the Atkins diet results primarily from restricting calories, not just reducing carbohydrates.

  But evidence on safety and efficacy is insufficient to recommend low-carbohydrate diets, especially for longer than three months or for people older than age 50, said lead researcher Dr. Dena Bravata of Stanford University.

In the zonisamide study, the researchers said "the precise mechanism is not known" for how the drug stimulates weight loss.

Fatigue was the only side effect reported more frequently in the zonisamide patients than in the placebo group. How it would stack up against drugs approved for weight loss is not known.

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