Healthy overweight and lean young men are subjected to an overfeeding during 56 days which corresponds to a supplement of 761 Kcal/day. During two exploration days (before : D0 et after : D56 overfeeding) they have ingested a breakfast with tracer (d31_palmitic acid, d31_C16, 20mg/kg) and blood and urine samples were collected every hour of each exploration day. The enrichment in deuterium was measured by gas chromatography-organic mass spectrometry (GC-OMS) in palmitic acid pool of lipid fractions.