Do you really know which diet is best for you?

When it comes to weight loss, conventional wisdom says choosing a diet you like may help you stick to it. But new research suggests that, in fact, the opposite may be true.

A study published in the Annals of Internal Medicine found that patients who were assigned a diet plan to follow by their doctors lost more weight than people who chose their own plan based on personal preferences.

Researchers looked at 207 outpatients who were either overweight or obese at a Veterans Affairs Medical Clinic in Durham, North Carolina. They randomly assigned the participants into two groups: half were prescribed either a low-fat, reduced-calorie diet or a low-carbohydrate diet without calorie restrictions; the others were allowed to chose which of those two diet plans they'd rather follow.

Throughout the 48-week study, participants were offered group and telephone counseling. Those who chose their own diet were given the option to switch at the 12-week mark, but only five chose to do so.

Contrary to what the researchers expected, those in the choice group lost less weight and reported more difficulty sticking to their diet than the patients who were assigned a dietary plan.

"I think it's a natural assumption to make that people will stick to a diet better if they choose it based on their food preferences, but what we found is that that's not really the best recommendation," the study's lead author Dr. William Yancy told CBS News.

Overall, the participants, the majority of whom were male with an average age of 55, lost about two more pounds when they were on a diet prescribed to them rather than on one they chose.

"It wasn't a large number and not statistically significant, but the surprising thing was that it was in the opposite direction than what we would have guessed," Yancy said.

Dieters who select their own plan may struggle more adhering to it, Yancy hypothesized, because picking a diet that allows them to eat food they like may make it harder for them. "If people choose a diet they prefer based on food preferences, they may have a more difficult time scaling back on their intake," he explained.

Yancy said the results suggest that future research should examine how to match the most effective diet to a patient based on other characteristics, such as their metabolic profile and maybe even genetic profile, rather than their taste and personal preference.