The objective of the present invention is to identify compounds having an inhibitory effect on adipocyte differentiation, and to provide pharmaceutical compositions and food compositions for prevention, improvement, or treatment of obesity or obesity related diseases. By enthusiastically studying natural products that inhibit the differentiation induction of adipocyte precursors into adipocytes, sesquiterpenoid derivatives, which are extracts from a Compositae plant, Calea, growing in Central and South America, were demonstrated to have an excellent inhibitory effect on adipocyte differentiation induction. Calea extract or the sesquiterpenoid derivatives are expected to be used in pharmaceutical compositions and food compositions for prevention, improvement, or treatment of obesity or obesity related diseases.