A team of Japanese researchers has discovered a powerful synergy between gut bacteria and an acetate supplement called AceCel that helps mice lose fat without losing muscle.
When combined with specific Bacteroides bacteria, acetate rewires metabolism, boosting fat burning and reducing sugar availability. This mechanism mimics fasting or a keto diet and could pave the way for new functional foods to fight obesity in humans.
Acetate and Gut Bacteria: A Surprising Duo Against Obesity
A team of researchers in Japan, led by Hiroshi Ohno at the RIKEN Center for Integrative Medical Sciences, has uncovered an exciting new approach to reducing obesity. Their study shows that giving the gut extra acetate, a natural compound, can lower both fat and liver mass in mice. But there’s a catch: this effect only works when specific gut bacteria called Bacteroides are also present. When these bacteria and acetate work together, they help the body burn more fat and remove excess sugars from the gut. The findings were recently published in Cell Metabolism.
Obesity is a major global health issue, affecting hundreds of millions of people. It is often linked to high intake of sugar and starchy foods and increases the risk of heart disease, type 2 diabetes, and cancer. Interestingly, eating fiber has been shown to reduce the risk of these very same diseases. Although humans cannot digest fiber, it reaches the large intestine where it is fermented by gut bacteria. This fermentation produces byproducts, some of which enter the bloodstream and help regulate metabolism.
AceCel: A Smart Acetate Delivery System
The most common of these byproducts is acetate, which is known to have some beneficial effects on host metabolism. Although this makes dietary fiber a good “prebiotic,” individual variation in the production of acetate and other useful byproducts limits its efficacy. To get around this problem, Ohno and his team previously developed a kind of acetate supplement by combining it with cellulose. AceCel ensures acetate reaches the distal large intestine, where it can work its magic.
Weight Loss Without Muscle Loss
In the new study, the team investigated how AceCel affects mouse metabolism and the composition of gut bacteria. They found that when given AceCel, both normal and obese mice lost weight without losing muscle mass. This was not true for other short-chain fatty-acid byproducts, meaning that acetate itself is the key. Further tests were designed to figure out how this was happening.
They next discovered that compared with mice on a normal diet, when AceCel-fed mice were resting, they generated more energy from burning liver fat and less from burning carbohydrates. This is similar to what happens when fasting or on a low-carb, keto diet, and promotes weight loss. Hypothesizing that the effects on the gut microbiome would also be similar, they analyzed the gut microbiota, finding that eating AceCel led mice to have more Bacteroides bacteria in their guts.
The Key: Acetate Plus Bacteroides Bacteria
They then tested AceCel in mice that had controlled gut microbiota: either no bacteria at all, or one of several Bacteroides species. They found that AceCel had no effect on body, liver, or fat mass in the gut-bacteria free mice, while three Bacteroides species had similar positive effects on each. This means that the specific combination of acetate and Bacteroides bacteria in the intestines is necessary for the observed weight loss to occur.
Sugar Reduction, Fat Burning, and Obesity Prevention
Digging deeper, they found that this combination leads to more fermentation of carbohydrates in the gut, meaning that there is less sugar available for the host to process. By eliminating the sugars, fat-derived energy is promoted, and less sugar is stored as glycogen in the liver, thus explaining how obesity is reduced.
“Developing a treatment or prevention strategy for obesity is an urgent issue that must be solved quickly,” says Ohno. “We found that acetylated cellulose can prevent obesity by modulating the function of the gut microbiome.”
“Our next step is to confirm the safety and efficacy of using acetylated cellulose to treat obesity in humans. If so, it could become an important ingredient in functional foods that prevent obesity.”
Reference: “Acetylated cellulose suppresses body mass gain through gut commensals consuming host-accessible carbohydrates” by Tadashi Takeuchi, Eiji Miyauchi, Yumiko Nakanishi, Yusuke Ito, Tamotsu Kato, Katsuki Yaguchi, Masami Kawasumi, Naoko Tachibana, Ayumi Ito, Shu Shimamoto, Akinobu Matsuyama, Nobuo Sasaki, Ikuo Kimura and Hiroshi Ohno, 16 May 2025, Cell Metabolism.
DOI: 10.1016/j.cmet.2025.04.013
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