High fibre diet may be good alternative to complex weight loss regimen, US study finds

BMJ 2015; 350 doi: (Published 19 February 2015) Cite this as: BMJ 2015;350:h965
  1. Michael McCarthy
  1. 1Seattle

A diet that simply encourages people to eat 30 g or more of fibre a day may be a good alternative to a far more complex weight loss regimen recommended by the American Heart Association (AHA), a US study has shown.

The study included 240 participants with metabolic syndrome whose average age was 52 and whose average body mass index was 35 kg/m2.1 Most (72%) of the participants were women, and 86% had at least a college education.

The participants were randomly assigned to two groups. One group was enrolled in a programme based on the AHA’s dietary recommendations for the management of metabolic syndrome; the second group was enrolled in the high fibre diet plan. For both groups, the interventions consisted of two individual sessions and 12 group sessions.

The primary outcome was weight change at 12 months. The researchers hypothesised that the high fibre group would lose more weight. Yunsheng Ma, of the University of Massachusetts Medical School in Worcester, Massachusetts, was the paper’s lead author.

The dietary goals of the AHA programme included consuming more vegetables, fruit, whole grains, and high fibre foods (≥30 g/day); consuming lean animal and vegetable proteins, including eating fish twice a week; reducing intake of sugary beverages; minimising sugar and sodium intake; and maintaining moderate to no alcohol intake.

Dietary targets for the AHA diet group included obtaining 50-55% of caloric intake from carbohydrates, 15-20% from protein, and 30-35% from fat. Saturated fat consumption was to be limited to less than 7% of energy, trans fat to less than 1% of energy, and cholesterol to less than 300 mg/day. Energy intake goals were calculated for each participant to achieve a weekly weight loss of 0.5-0.9 kg, a reduction of 500-1000 calories a day.

Participants in the high fibre group, on the other hand, simply received instructions on how to increase their fibre intake to at least 30 g a day (the current average daily dietary fibre intake in the United States is only 16 g). No physical activity recommendations were made, and no caloric goals were set.

At 12 months 89% of the participants had completed the programme: 15 (12.6%) had dropped out from the AHA diet group and 12 (9.9%) from the high fibre group (P=0.55). Weight loss was greater in the AHA diet group (mean change –2.7 kg (95% confidence interval –3.5 to –2.0)) than in the high fibre group (–2.1 kg (–2.9 to –1.3)). The mean difference between groups was 0.6 kg (–0.5 to 1.7).

But many other outcomes were comparable. Diastolic and systolic blood pressures decreased during the trial in both groups. Systolic blood pressure decreased in the AHA diet group (−2.5 mm Hg (−4.5 to −0.6)) and in the high fibre group (−1.5 mm Hg (−3.5 to 0.5)); and diastolic blood pressure fell in the AHA diet group (−1.7 mm Hg (−3.3 to −0.1)) and the high fibre group (−0.8 mm Hg (−2.4 to 0.9)). The between group differences were not significant.

No significant between group differences were found in factors such as plasma insulin; high and low density lipoprotein and cholesterol levels; homeostasis model assessment of insulin resistance scores; or measures of inflammation such as high sensitivity C reactive protein and tumour necrosis factor alpha receptor 2 levels.

The researchers concluded, “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.”


Cite this as: BMJ 2015;350:h965


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