Wondering why a diet's not working for you? Stop watching your waistline and consider something a little deeper — like the feces lodged in your intestines.
A study this month in the International Journal of Obesity found that a specific diet's success may come down to the bacteria mix in one's gut, as observed in stool samples.
Danish researchers looked specifically at the ratio of bacteria known as Prevotella and Bacteroides in 62 overweight participants. Then, researchers had participants stick to a diet for 26 weeks, either the New Nordic Diet —a high-fiber regimen —or an average Danish diet.
Participants shed about 7 pounds more on the high-fiber diet than the average diet ifthey had a high ratio of Prevotella to Bacteroides, the study found. But among those with a low ratio of the bacteria, no significant difference between the two diets was found.
The results show that knowledge of a person's specific biochemistry can likely optimize weight loss better than a one-size-fits-all approach to dieting, researchers said in a statement.
"The study shows that only about half of the population will lose weight if they eat in accordance with the Danish national dietary recommendations and eat more fruit, vegetables, fibers and whole grains," said Mads F. Hjorth, a co-author of the study and nutrition professor at the University of Copenhagen.
"The other half of the population doesn't seem to gain any benefit in weight from this change of diet," Hjorth said, and "should focus on other diet and physical activity recommendations until a strategy that works especially well for them is identified."