HMN 2025: How Obese teens given healthy gut bacteria show lasting drop in diabetes risk

Eight years ago, 87 obese adolescents took part in a study to see whether fecal transfer (taking “good” gut bacteria from healthy donors and giving them in capsule form to people with a less healthy microbiome) would make a difference to their health and weight.

Four years later, a follow-up study, published this week in the journal Nature Communications, suggests some significant health benefits from that single gut bug transfer, with the original overweight teens having reduced risk for a number of metabolic changes which can lead to heart disease, stroke and diabetes.

Obesity is a significant health problem in New Zealand and elsewhere in the world. In Aotearoa, one in ten children and one in three adults—the third highest rate in the OECD—are classified as obese, according to Ministry of Health figures.

Obese teenagers very often grow up to be obese adults, and obese adults are more likely to suffer from a number of health problems, including type 2 diabetes, heart disease, stroke, cancer, osteoarthritis, sleep apnea and problems with pregnancy and birth.

Professor Wayne Cutfield says four years after the original study, the group that had received the gut bugs hadn’t lost weight. However, unlike the placebo group, they hadn’t put it on. The treatment group were on average 11kg lighter than those who had the placebo, although this was not considered statistically significant.

More important, was the impact on metabolic syndrome, Cutfield says. Metabolic syndrome is a cluster of five conditions—high blood pressure, high blood sugar, large waist circumference, high triglycerides (fat in the blood), and low HDL (‘good’) cholesterol.

“More than one in three of the original teenage participants in our study had metabolic syndrome,” Cutfield says. “Metabolic syndrome has severe consequences, including a doubling in risk of death from heart disease or stroke and a five-fold increased risk of type 2 diabetes.

“What is impressive is that just a single FMT [fecal microbiota transplantation] treatment produced a dramatic reduction in metabolic syndrome that lasted at least four years. This means participants are at much lower risk of developing diabetes and heart disease over the long term.”

Professor Justin O’Sullivan says another key finding in the follow-up study was that four years after the original fecal transfer, the introduced healthy bacteria were still present and thriving in the guts of the participants who had taken the capsules.

“It really makes us think about the timeframes over which we look for the impacts of microbiome-based treatments.”

O’Sullivan says the team is now working to identify and isolate a small number of “good” gut bacteria likely to be the ones responsible for the beneficial health outcomes from the study. “Imagine being able to program your microbiome to reduce the risk of conditions before they occur. This work is paving the way for the next generation of probiotics that target specific conditions through sustained changes to the microbiome.”

Cutfield says commercialization is the final goal, and Liggins is working towards producing and trialing capsules.

“Our holy grail is to develop a super mix of bacteria that can be taken to prevent or moderate metabolic syndrome. The first step is to prove our bespoke combination of bacteria actually works.”