The findings suggest that gut health is as important as caloric intake when it comes to addressing low body weight.
Researchers from Fujita Health University and Symbiosis Solutions recommended pre- and probiotics supplementation to improve the gut microbiota and for a healthier body weight.
“Not only the amount of energy or the ratio of protein, fat, carbohydrate, but actively consuming dietary fiber and fermented foods may lead to weight improvement in underweight individuals by causing changes in the gut microbiota," said Dr. Katsumi Iizuka, Professor at the Department of Clinical Nutrition, Fujita Health University who led the research.
Research method
Eighty women aged 20 to 39 were recruited, half of them were underweight and the other half had BMI in the normal range of between 18.5 to less than 25.
Using the Food Frequency Questionnaire, their consumption of meat, fish, eggs, dairy products, soybeans, green and yellow vegetables, seaweed, fruit, tubers, and fats and oil were assessed.
Stool samples were also collected for gut microbiota assessment.
Key findings
Writing in Nutrients, the researchers reported no significant differences in the types of foods consumed, as well as the energy, fat, protein, carbohydrate, and dietary fiber intake between the underweight and normal weight groups.
However, there was significant differences when it comes to the gut microbiota.
For example, the underweight group had a significantly lower α diversity of the gut microbiota than the normal weight group.
Underweight women also had a significantly higher amount of Bacteroides, Enterocloster, and Erysipelatoclostridium, which are linked to inflammation.
Citing studies published in 2023 and 2015, the researchers noted that an increase in Bacteroides and Erysipelatoclostridium may be accompanied by inflammatory metabolites.
The normal weight group, on the other hand, had a higher amount of bacteria like Dorea - which is associated with fiber fermentation and short-chain fatty acid (SCFA) production.
A decrease in Dorea may suggest a reduction in dietary fiber intake, and may also lead to a reduced supply of anti-inflammatory SCFAs, the researchers highlighted, citing a 2022 study.
“There were no differences between the two groups in terms of energy intake, protein intake, or dietary fiber intake, nor were there differences in the alpha or beta diversity of dietary patterns,” wrote the researchers.
“Considering that underweight women have been reported to have decreased lymphocyte counts and impaired immune function, the increased presence of Bacteroides, Enterocloster, and Erysipelatoclostridiumin, the underweight group may reflect a greater burden of opportunistic bacteria contributing to intestinal inflammation and compromised mucosal barrier function.
“Further investigation is needed to determine whether individuals with low body fat percentages experience an increase in gut bacteria related to inflammation in underweight groups,” they concluded.
Source: Nutrients. 17(20), 3265. doi: 10.3390/nu17203265. “Gut Microbiota α- and β-Diversity, but Not Dietary Patterns, Differ Between Underweight and Normal-Weight Japanese Women Aged 20–39 Years”. Authors: Yamamoto-Wada R, et al.
