With more research focusing on the effect of gut health, more researchers are exploring the relationship between gut flora and weight loss. But could some types of bacteria predict whether you can successfully lose weight on specific types of diet?



A person’s diet can have a significant impact on their microbiome, or gut flora. But researchers are starting to find that differences in gut flora can also have influence on the impact of the diet, especially in terms of obesity management.

One bacterial strain of interest is Prevotella. Prevotella is associated with a high dietary fibre and carbohydrate. On the other hand, Bacteroides is associated with a Western-style diet that is lower in fibre and higher in fat. One study found that Bacteroides displace Prevotella after citizens from Thailand immigrated to the USA, causing them to lose their fibre-degrading capacity in the gut.

Recent studies have found that people with an abundance of Prevotella in the gut lose more weight on diets that are rich in fibre compared to those with low levels of the bacteria.


The study

Researchers analysed a previous 6-week parallel randomised trial. The study looked at the difference in body weight changes when participants consumed a whole-grain wheat/rye or refined-wheat diet.

46 participants were stratified by their baseline Prevotella:Bacteroides ratio and Prevotella abundances. 24 with no Prevotella present were analysed separated.

There was no caloric restriction for any of the groups. All subjects were provided with breakfast cereals, pasta, kernels, crisp bread and bread products that were either whole-grain or refined-wheat based. The whole-grain diet group consumed an average of 33g of fibre per day, whereas the refined-wheat diet group consumed an average of 23g per day.

Participants completed a 4-day food record of food and beverages at baseline and during the last week of intervention.


The findings

Participants with high Prevotella abundances lost 1.8kg more on the whole-grain diet than on the refined-wheat diet. Those with low Prevotella remained relatively weight-stable.

Participants who had no Prevotella present lost 1.59kg more on the whole-grain diet than those on the refined-wheat diet, with those consuming refined-wheat actually gaining an average of 0.63kg.

There were no changes in appetite sensation, glucose metabolism or faecal short-chain fatty acids associated with the different Prevotella groups. There was no correlation found between Prevotella:Bacteroides ratio and weight changes in either the whole-grain or refined-wheat diet groups.



The researchers concluded that healthy, overweight adults with high Prevotella abundances lost more weight than those with low Prevotella when consuming a high-fibre whole-grain based diet for 6 weeks.

People with no Prevotella present responded differently to those with low Prevotella, losing weight on a whole-grain diet but gaining a small amount of weight on the refined-wheat diet.

They noted that the findings further supported differences in gut flora as a potential biomarker for personalised nutrition and obesity management.



Christensen, L., Vuholm, S., Roager, H.M., Nielsen, D.S., Krych, L., Kristensen, M., Astrup, A. and Hjorth, M.F., 2019. Prevotella Abundance Predicts Weight Loss Success in Healthy, Overweight Adults Consuming a Whole-Grain Diet Ad Libitum: A Post Hoc Analysis of a 6-Wk Randomized Controlled Trial. The Journal of nutrition.