Single Diet Modification May Improve Metabolic Syndrome

Susan London

February 17, 2015

A diet that focuses solely on increasing fiber intake works about as well as a more complex American Heart Association (AHA)-compliant diet for promoting weight loss and improving risk profile among patients with metabolic syndrome, suggests a randomized trial reported in the February 17 issue of the Annals of Internal Medicine.

"Although the primary goal of our study (for the high-fiber diet group to achieve superior weight loss) was not met, we found that a single component dietary intervention can achieve clinically meaningful weight loss similar to that of the multicomponent AHA diet," the investigators write. "We were also encouraged by the improvements in blood pressure, dietary quality, and insulin resistance, all of which are integral in the prevention of diabetes, cardiovascular disease, and management of the metabolic syndrome."

Yunsheng Ma, MD, PhD, from the Division of Preventive and Behavioral Medicine, Department of Medicine, University of Massachusetts Medical School, Worcester, and colleagues enrolled 240 adult patients with metabolic syndrome in the trial. They were 52 years old, on average, and predominantly female (72%.1), white (87.4%), and with at least a college education (86.1%).

The patients were randomly assigned to a high-fiber diet group or to an AHA diet group. Participants in the high-fiber group received instruction on increasing their fiber intake to at least 30 g/day. Participants in the AHA diet group received instruction on increasing fiber intake, adhering to individualized goals for caloric and saturated fat intake, and following other practices recommended in the guidelines (eg, eating fish twice weekly, minimizing sugar and sodium intake, and limiting alcohol). Neither group was given any instruction on physical activity.

At 12 months, there was no significant difference in the amount of weight lost between the two groups, at 2.1 kg in the high-fiber group (95% confidence interval [CI], 2.9 - 1.3 kg) compared with 2.7 kg (95% CI, 3.5 - 2.0 kg) in the AHA diet group. Moreover, both groups showed improvements in blood pressure, dietary quality, insulin resistance, and fasting plasma insulin levels.

There was a trend whereby patients in the high-fiber group were somewhat more likely than those in the AHA diet group to develop diabetes (a hemoglobin A1c level of at least 6.5%): seven patients in the former group became diabetic vs one patient in the latter.

The dropout rate was 9.9% in the high-fiber diet group and 12.6% in the AHA diet group, which was a nonsignificant difference.

"The more complex AHA diet may result in up to 1.7 kg more weight loss; however, a simplified approach to weight reduction emphasizing only increased fiber intake may be a reasonable alternative for persons with difficulty adhering to more complicated diet regimens," the investigators conclude.

"A dietary message that focuses on 1 dietary component, such as dietary fiber, is permissive — it encourages an increase in a healthy behavior — versus the AHA diet's restrictive message, which advises persons to limit an unhealthy behavior."

"Drawbacks to the fiber-focused message may include missed information about other important dietary metrics," they acknowledge. "However, our study showed that untargeted aspects of diet improved in the high-fiber diet group (for example, the ratio of white vs. red meat consumed), possibly due to substituting high-fiber foods for less healthy foods."

The authors have disclosed no relevant financial relationships.

Ann Intern Med. 2015;162:248-257. Abstract

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