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News Article

High fibre diets may only aid weight loss for some


Weight loss success with high fibre diets may depend on gut microbe populations

The increasingly popular fibre-rich "New Nordic Diet" might not work for everyone. Its success depends on the particular combination of bacteria in the intestines of the dieter finds a study reported in International Journal of Obesity. The study, led by Mads Hjorth and Arne Astrup of the Department of Nutrition, Exercise and Sports at the University of Copenhagen in Denmark, was funded by Gelesis Inc http://www.gelesis.com/our-approach.php, a producer of fibre supplements for weight loss.

The background: fibre and weight loss

A recent review by Brownlee and colleagues sets out the situation with dietary fibre research: observational studies suggest that diets high in fibre and adhering to a diet high in fruit, vegetables and wholegrains both result in less weight gain. In practice, however, randomised controlled trials assessing interventions with fibre don’t always succeed.

Resident microbes ferment soluble fibres in the gut and so are important for understanding what is happening with fibre and weight loss. The products from fibre fermentation may affect satiety and other metabolic responses. The development of more powerful genomic analysis is beginning to help researchers untangle what is going on in terms of the bacterial populations.

So far researchers have found that dietary fibre intake can alter the microbial populations in the gut, and a high fibre diet seems to increase diversity and amounts of Prevotella spp. While a high fat diet seems to foster Bacteroides species. Studies also suggest that the obese people have an altered microbial profile compared with lean subjects although the reasons for this difference are unclear. Fecal transplantation could be a way of influencing weight gain and loss. (see Further Reading for background references)

Study details

62 overweight participants followed either the "New Nordic Diet" or the "Average Danish Diet". Of the two the New Nordic diet is more fibre-rich and places greater emphasis on wholefoods such as vegetables and fruits. The participants' weight and body measurements were taken before and after they started their 26-week diets.

The researchers placed participants into two different enterotype or gut bacteria groups based on the abundance of Prevotella bacteria types found in their intestines compared to Bacteroides species. About half of the participants fell in the high volume Prevotella-to-Bacteroides group, whereas the other half were placed in the low ratio group. After the initial 26-week study period, all 62 participants followed the New Nordic Diet for another year.

On average, the 31 subjects who ate the New Nordic Diet for 26 weeks lost 3.5 kilograms, whereas the 23 subjects following the Average Danish Diet lost 1.7 kilograms. The New Nordic Diet worked best for participants in the high volume Prevotella group. They lost 3.15 kilograms more body fat when they followed the New Nordic Diet compared to the Average Danish Diet. Their waistlines also decreased more significantly, and they maintained weight loss after following the diet for one year. The type of diet followed had no influence on how much weight participants in the low ratio group lost.

"People with a high Prevotella/Bacteroides ratio were more susceptible to body fat loss on a diet rich in fibre and wholegrain compared to an average Danish diet," Hjorth explains.

"The health promoting aspects of the New Nordic Diet in terms of body weight regulation seem mainly to apply to a subset of the population," he adds. "This could apply to as much as half of the population."

Hjorth says that research into the human gut microbiota is increasingly playing a role in personalizing nutrition. He believes that the two relatively stable groups or enterotypes of bacteria species into which people can be grouped could be valuable markers to predict whether specific diets will work for them or not.

Reference

Pre-treatment microbial Prevotella-to-Bacteroides ratio, determines body fat loss success during a 6-month randomized controlled diet intervention. M F Hjorth, H M Roager, T M Larsen, S K Poulsen T R Licht, M I Bahl, Y Zohar and A Astrup, International Journal of Obesity accepted article; doi: 10.1038/ijo.2017.220

MFH, YZ, and AA are co-inventers on a pending provisional patent application on the use of biomarkers for prediction of weight loss responses.

Article details

  • Author(s)
  • I. Hoskins
  • Date
  • 15 September 2017
  • Subject(s)
  • Nutrition & health