LEP and myalgic encephalomeyelitis/chronic fatigue syndrome: Of note, serum and CSF leptin levels were significantly lower in patients with CFS compared to the SFS group (0.6 ± 0.07 vs 3.7 ± 0.8 ng/ml for serum leptin and 0.24 ± 0.08 vs 1.48 ± 0.3 ng/ml for CSF leptin, respectively; P < 0.05) Table 2.