Low-energy diets are often used for weight loss interventions, but the success rate can vary greatly. Recent studies suggest that these diets are linked to changes to the gut microbiota, which may influence the metabolism and resulting weight loss. Given this link, is it possible that your microbiota can predict whether you will successfully lose weight on a low-energy diet? Background There is significant variation in the success of diet-induced weight loss due to multiple factors. But one factor of note is the state of an individual’s gut health, particularly that of their microbiota. The gut microbiota has influences across the human body, including nutrient absorption, inflammation and even metabolism. Given this, it’s possible that your gut flora could help to support you in weight loss or hinder your efforts. But the research on the link between the microbiota and low-energy diets & weight loss is conflicting. The study Researchers designed a secondary study of data from PREVIEW – a multi-centred randomised controlled trial of a 3-year lifestyle intervention to prevent type 2 diabetes. The original trial consisted of 2224 adults with a BMI ≥25 and pre-diabetes. They were aged between 25-70 years, had a stable body weight for at least 2 months prior, and were not using glucose medication or had any medication changes in the 3 months prior. Exclusion criteria included type 2 diabetes, cardiovascular disease, liver disease, gastrointestinal disease, kidney disease, cancer, bariatric surgery or major surgery in the previous 3 months, pregnancy and breastfeeding. Participants were provided with 8 weeks of total meal replacement sachets. The diet provided 810kJ per day, with 44% energy from protein, 41% carbohydrate and 15% fat. They could also add up to 400g of non-starchy vegetables. For the secondary study, the researchers took data from a cohort of participants in New Zealand and Finland, with a total of 211 participants. There was no reported antibiotic use in the group 3 months prior or during the low energy diet (LED). Faecal samples were used to assess the contents of the gut microbiota, along with assessment of butyrate production. The findings In the original trial, the participants lost an average of 11.5% body weight and 22% body fat during the LED. The overall composition of the microbiota changed significantly and consistently from baseline to post-LED with increased richness and diversity. Post-intervention, the abundance of several microbe genera known to be associated with metabolic improvements was significantly higher. There was a decrease in other species and genera, as well as reduced butyrate production capacity. The changes in microbiota composition were significantly associated with body weight loss. In fact, the baseline microbiota features explained around 25% of variation in total body fat change. Conclusions The researchers concluded that the gut microbiota, along with individual taxa, were significantly influenced by a low-energy intervention. They also correlated with changes in total body fat and body weight in overweight and pre-diabetic individuals. Despite the variation between participants, the baseline microbiota was a strong predictor of total body fat change during energy restriction. However, some limitations were noted by the researchers. The two different methods for total body fat at the two study sites may have led to differences in the fat mass and fat-free mass. To account for this, they analysed change from baseline data to ensure the results were more comparable. There is also the possibility that natural fluctuations in gut flora were partly involved in the observed changes. Further studies could help to add to the information surrounding the gut microbiota, weight loss and the complex relationships between the two. References Jian, C., Silvestre, M.P., Middleton, D., Korpela, K., Jalo, E., Broderick, D., de Vos, W.M., Fogelholm, M., Taylor, M.W., Raben, A. and Poppitt, S., 2022. Gut microbiota predicts body fat change following a low-energy diet: a PREVIEW intervention study. Genome medicine, 14(1), pp.1-18. Raben, A., Vestentoft, P.S., Brand‐Miller, J., Jalo, E., Drummen, M., Simpson, L., Martinez, J.A., Handjieva‐Darlenska, T., Stratton, G., Huttunen‐Lenz, M. and Lam, T., 2021. The PREVIEW intervention study: Results from a 3‐year randomized 2 x 2 factorial multinational trial investigating the role of protein, glycaemic index and physical activity for prevention of type 2 diabetes. Diabetes, obesity and metabolism, 23(2), pp.324-337.