The 41st Annual scientific meeting of the Physiology Society of Thailand was held at Sri Savarindhira building, Faculty of Medicine Siriraj Hospital during 2-4th of May 2012.  Associated Professor Supatra Lohsiriwat, the president of the Physiology Society of Thailand, and Assistant Professor Wattana Watanapa, the head of Physiology department were the chairman and the secretary of the organizing committee.  The topic of the meeting was “Obesity: size does matter”. There were 2 honorary lectures and 5 symposia covering all aspects of Obesity including the prevalence, impact, pathophysiology, health problem, prevention, treatment, and also the future and ongoing research in obesity. There were over 200 participants and 50 abstracts submitted to this meeting from universities all over Thailand.  This meeting was successful and the next meeting will be held by Srinakarin Viroj University.