Metformin is one of the few drugs in the treatment of DM2 that is associated with moderate weight loss. Interestingly, patients using metformin show an increased 18F-FDG-uptake in the colon. Whether this higher uptake of glucose also cause an increase in core temperature and/or an increase in energy expenditure is not known. The cause for this increase in glucose uptake in the colon by metformin use is unknown. Also, it is unknown whether this increase in glucose uptake results in an increased energy expenditure and/or an increase in core body temperature.