Figure 5:First column; raw plasma leptin levels in six healthy men. Second column; leptin levels were averaged for six 4-h time periods and expressed as percentage of the 24-h average. Asterisk indicates that leptin levels in a specific time period are statistically different from those at the 8:00-12:00 period. Third column; spectral analysis of the detrended data series showing circadian (24h) periodicity in leptin levels. Reprinted by permission from Macmillan Publishers Ltd: Nature Medicine, ref. (25) , copyright 1997.