Surprising new research suggests letting patients choose their own diet plan based on personal preference could prevent them from losing weight.

Since diet adherence is one of the greatest predictors of weight loss, researchers hypothesiczed letting patients choose a diet they liked could help them stick to it and lose more weight, the American College of Physicians reported.

They randomly assigned participants to one of two groups: one in which the patients were allowed to choose their diet and one in which they were assigned a diet by their physician. The "choice" participants were allowed to choose from a "low-carbohydrate diet without calorie restriction or a low-fat diet combined with calorie restriction." The "comparator" group was randomly assigned to either diet. Both groups were offered telephone counseling session throughout the 48-week study. At 12 weeks, the "choice" participants were given the option to switch diets, but very few took that option.

Contrary to the researchers' hypothesis, the patients in the choice group proved to lose less weight and reported lower rates of dietary adherence and weight-related quality of life compared with those who were assigned their diet.

"These results suggest that choosing a diet based on food preferences may make it difficult for dieters to scale down on the amount that they eat. Future research should consider matching the most effective diet to an individual using other patient characteristics such as metabolic profile or even genetic profile," the researchers stated.

The findings were published in a recent edition of the journal Annals of Internal Medicine.