The objective of this study was to describe long-term detraining effects on lipid profile in previously highly endurance-trained athletes. The study design was longitudinal, with a 2-yr follow-up study of changes in lipid profile during hard training and detraining. Ten subjects trained for 2 yr (22 h/wk; two 47-wk training periods with a 5-wk recovery period), and the 10 others stopped training after wk 47. Main blood lipid profile parameters, energy intake, and body composition were measured at baseline (wk 1) and at wk 24, 47, 52, 76, and 99. Although food caloric intake was reduced (2411 ± 256 vs. 5697 ± 455 kcal/d, detraining vs. training), detraining induced a decrease in high density lipoprotein cholesterol and increases in fat mass (by 6.5 ± 1.1 kg), body mass index, leptin, low density lipoprotein cholesterol, low density lipoprotein/high density lipoprotein ratio, and apolipoprotein B, although insulin resistance (determined by homeostasis model assessment) stabilization had previously occurred. Further disorders appeared in triglycerides (TG) metabolism during detraining, with a persistent increase in TG (from 1.0 ± 0.3 to 1.4 ± 0.3 mmol/liter), whereas glycerol decreased (from 88 ± 9 to 73 ± 8 μmol/liter), and very low density lipoprotein-TG, chylomicrons, and apolipoprotein C3 remained stable. Plasma lipoprotein lipase activity decreased whereas hepatic lipase activity remained stable. As well as a rapid loss of endurance-training benefits for the cholesterolemic profile, detraining also induced disorders in TG metabolism, possibly as a result of the elevated TG turnover acquired with long-term hard training.