Which Diet Gives the Best Bang for Your Buck?

— -- Need some help losing weight? The diet program Weight Watchers and the weight loss drug Qsymia may be the best bang for your buck, a new study found.

Researchers from Duke University compared the costs and effectiveness of three diet programs and three weight loss medications and found that Weight Watchers came out on top with a price tag of $155 per kilogram lost.

“[Weight Watchers is] a program that holds you accountable,” said ABC News’ senior medical contributor Dr. Jennifer Ashton. “Whether through their meal plans or through their meetings, this helps you stay on track.”

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The average annual cost of Weight Watchers was $377, according to the study. And users lost an average of 2.4 kilograms or 5.3 pounds.

“It’s about restricting portion size,” Ashton said of the point system-based program. “It’s not about depriving you of food. That’s key.”

Qsymia was a close second, clocking in at $204 per kilo, according to the study. Ashton said some of her patients have had impressive results with the drug.

“They were obese to morbidly obese, and most lost significant weight,” she said.

Also included in the study were the weight loss drugs Vtrim at $213 per kilo, Lorcaserin at $545 per kilo and Orlistat at $546 per kilo, as well as the diet program Jenny Craig, with an average cost effectiveness ranging from $338 to $424 per kilo depending on the amount of food purchased.

But the price of dieting isn’t the only cost to consider, Ashton said, citing the emotional, psychological and social costs of obesity, which affects one in three American adults.

“We need to look at the big picture when we think as a nation of how to deal with the issue of obesity,” she said.