The prevalence of obesity represents a major threat to public health as it often accompanied with a panel of diseases due to low grade chronic inflammation, including type 2 diabetes, high blood pressure, cardiovascular diseases, stroke, etc. There is a great need for safe and effective anti-obesity treatments. In a recent publication, researchers showed that the water extract of a special mushroom G. ludidum (WEGL) reduced obesity in high fat diet fed (HFD) mice by altering gut microbiome. And this anti-obesity effect is transmissible, demonstrated by faeces transplantation from WEGL treated mice to HFD mice. This group of researchers were also able to pinpoint the active ingredient in WEGL, the high molecular weight polysaccharides (>300kDa), which exert the microbiota-modulating and anti-obesity effects.