The present invention provides a use of Flammulina sp. extract and its compounds for enhancing the gene expression level of ATGL, LIPE, UCP1, and/or UCP2, and/or inhibiting fat accumulation. The Flammulina velutipes extract and its compounds can effectively promote the metabolism of fat, and reduce the accumulation of fatty oil droplets in fat cells to reduce the fat accumulation. The Flammulina velutipes extracts is prepared by extracting Flammulina velutipes using water, alcohols, or mixtures of water and alcohols as solvents, and the Flammulina velutipes extract contains an effective component of hypoxanthine, or uracil.本發明提供一種小火菇屬萃取物與其化合物用於提升ATGL基因、LIPE基因、UCP1基因、及/或UCP2基因表現量、及/或抑制脂肪累積的用途。本發明之小火菇屬萃取物能有效促進代謝脂肪的活性，並有效減少脂肪細胞中脂肪油滴的堆積，以減少脂肪的堆積，進而達到減脂的功效。其中，該小火菇屬萃取物係小火菇屬以水、醇、或醇水混合物之溶劑所萃取而得，且該小火菇屬萃取物含有次黃嘌呤、或尿嘧啶之效性成分。
