The study, published in Nature Communications, suggested Ganoderma lucidum slowed weight gain by altering bacteria in the gut.
The researchers suggested the mushroom could eventually be used in the treatment of obesity.
Experts said the science was good, but putting mushroom extract in cans of cola would not help people lose weight.
G. lucidum has traditionally been sold for “health and longevity” say researchers at Chang Gung University.
They analysed the impact of the fungus on mice being fed a high-fat diet.
Those on just a high-fat diet reached 42g after their first two months whereas mice that were also fed a high dose of mushroom extract reached only 35g.
Mice were still much slimmer if they were fed a normal diet.
In their report, the team said mushroom extract “may be used as pre-biotics to reduce body weight gain, chronic inflammation and insulin resistance [type 2 diabetes] in obese individuals.”
Although this would, they said, need further testing in people.
The team in Taiwan showed that adding the mushroom to the mice’s meals altered the types of bacteria living in the gut.