In this study, the researchers aimed to see if reishi was effective in preventing obesity. They gave mice different amounts of reishi or placebo and either a normal diet or a high-fat diet for eight weeks. All mice on the high-fat diet gained a lot of weight and body fat, but those given reishi did not gain as much weight or body fat. The reishi supplement did not have an effect on mice fed a normal diet. The supplement appeared to work by improving the number of “good” bacteria in the gut and through reducing inflammation. Some studies have suggested that chronic inflammation and an increased number of “bad” bacteria in the gut are linked to obesity in humans.