Extreme mental focus such as preparing for an exam or just solving problems that require intense concentration can actually drain the brain. Since the brain has a limited capacity to store fuel, the results can be similar to using stored energy from caloric expenditure through physical movement. This is the reason why college students not only eat poorly but also overeat. Scientists experimented with thirty eight college students. After 35 minutes of sitting quietly in a peaceful setting to establish a baseline for what they would normally consume, all were given as much pizza as they wished. After a few weeks they were called back and were all given intense college exams that required extreme mental focus. Afterwards, half were given pizza to consume and half were put on a treadmill. The group on the treadmill consumed less than they would normally consume while the other group consumed much more. The increased flow of fuel-rich blood to the brain brought on by intense exercise increased both the amount of blood sugar and lactate circulating in the blood. This in turn reduced the desire to overeat by feeding an exhausted brain.