Little effect seen from patient choice in low-carb vs. low-fat diets

Despite a theory that patient choice would positively affect weight loss when given the option of behavioral modifications, data presented at Obesity Week 2014 showed that the diet chosen may have a greater effect.

“The research is premised on several previous trials that have compared a number of different diets … with many of the results showing multiple diets can work. None are clearly superior, so we should give patients a choice among the diets,” William S. Yancy Jr., MD, told Endocrine Today. “Right there is a major advance from previous years when there weren’t too many diet options provided to patients. More recently, the recommendations have been to consider other diets, but the conclusion that we should allow patients to choose from them makes a lot of sense intuitively but hasn’t been tested very well.”

Choice vs. assigned

Yancy, an associate professor of medicine at Duke University, said the researchers recruited 207 patients from the VA Medical Center and randomly assigned them to the control arm (n=102), in which they were further randomly assigned to either low-fat or low-carbohydrate diets, or the choice arm (n=105). In the choice arm, patients were brought in for an educational session in which researchers explained their individual responses to the Geiselman Food Preference Questionnaire to best explain how their food choices fit into the diet options.

“Then we went over what those diets looked like, which foods were emphasized, which were de-emphasized, which ones they’d have to stay away from, and the pros and cons of both the diets. We basically gave them a message that it’s not clear one is better than the other in terms of health. They’re both felt to have beneficial health impacts and it’s up to you to choose which diet you want to follow,” Yancy said.

Once decided, the two diet groups followed the same procedures: regular visits for 6 months and then motivational phone calls and more sporadic visits.

Surprising results

At 48 weeks, the choice arm had a –4.2% body weight change while the control arm had a –5.3% change (difference of 1.1%; 95% CI, 0-2.2). Additionally, there were no significant differences between groups for adherence, activity or quality of life.

“The results were surprising to us. We expected that adherence and weight loss would be better in the group that got to choose and, lo and behold, it wasn’t better. In some of the analysis we did, it seemed it might have been less effective to allow people to choose,” Yancy said.

The researchers investigated further to see if the diet either chosen or assigned had a differential effect on weight loss. They found that although there was no difference in the control arm, patients who chose a low-fat diet lost 3.5% of their body weight while those who chose low-carbohydrate diets lost 6.2% (P=.02).

“The diet did seem to matter,” Yancy said. Still, the difference in the arms was not enough to eliminate the option of choice.

“It seems to make sense to allow patients to choose, but it’s not really clear that it helps people adhere to the diet and succeed with the diet,” he said. “The differences between the arms was not huge, so we shouldn’t avoid giving people the choice, but we should also keep in mind that giving them a choice might not maximize their benefit. … Giving patients a choice — and giving them an informed choice particularly — is a generally accepted and helpful way to interact with patients.”

For more information:

Yancy WS. T-3011-OR. Presented at: Obesity Week; Nov. 2-7, 2014; Boston.

Disclosure: Yancy reports no relevant financial disclosures.