CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) is a trial currently underway in the U.S. to study the effects of prolonged calorie restriction on healthy human subjects. The second, larger, phase of CALERIE began in 2007. The participants are subjected to a 25% calorie restriction over a 2-year period, and several physiological variables are regularly monitored. Participants are paid US$5,000 at Tufts and Pennington and $2,400 at Washington University. As of October 2009 the study had 132 participants and was still accepting new ones.