Four popular diets are all effective when it comes to shedding pounds and reducing heart disease risks -- as long as dieters follow them closely, according to a new study.

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Researchers at Tufts-New England Medical Center assigned 40 overweight people to each of four diets -- Atkins, Zone, Weight Watchers, and an Omish low-fat vegetarian diet. The participants ranged in age from 22 to 72, and most were 30 to 80 pounds overweight.

After a year, 42 percent of the participants had stopped following their assigned diet. But of those who stuck to the diets, participants lost an average of 5 percent of their body weight, regardless of the diet they followed. People who followed their diet more closely lost even more weight, said Dr. Michael Dansinger, the study's lead researcher.

The dieters also reduced their heart disease risk by an average of 5 to 15 percent.

The Omish diet, which focuses on low-fat vegetarian food, was best for lowering LDL, or "bad," cholesterol levels, while the other diets were better at raising HDL, or "good," cholesterol levels.

But Dansinger, who presented the study's findings Sunday at a meeting of the American Heart Association, said the key to long-term weight-loss success is finding a plan you can stick to, and that won't be the same plan for everyone.

Dansinger noted that low-carb diets haven't been proved to reduce heart attacks, and more detailed studies need to be conducted on the effects of popular diets.

He noted that, with the study's results, the challenge is for doctors to work with overweight patients to devise a dieting plan that fits the patient's food preferences, lifestyle, and medical profile.

Additional Resources:

• ZonePerfect.com
• Atkins.com
• WeightWatchers.com
• Vegetiarian Diets