The present study assessed the effects of a diet and exercise intervention in jockeys on body composition, metabolism, bone and mental health. 10 jockeys followed an individually prescribed 6-wk diet (Carbohydrate = 2.5-3.5g/kg, Protein = 2.5 g/kg, Fat = 1.0g/kg). Body mass (59.2±4.6 vs. 57.6±4.5kg), fat mass (7.5±3.5 vs. 6.2±2.6) and body fat (13.1 ±5.9 vs. 11.5±4.9%) all decreased (P<0.05) from pre to post-intervention whilst lean mass (47.1 ±5.3 vs. 47.0±5.5 kg) was maintained (P = 0.80). RMR (1703±329 vs. 1975±313kcal.d-1), VO2max (3.8± 0.8 vs. 4.1±0.7L/min-1) chest strength (65±11 vs. 71 ±13 kg), leg strength (160±28 vs. 175 ±29 kg) and jumping height (40 ±6 vs. 48±5cm) significantly increased (P<0.05). Bone health (DXA) did not change (P>0.05) at hip (-1.04±1.29 vs. -0.76±0.71) or lumbar sites (-1.32±0.76 vs. -1.31 ±0.77). Psychometrics (GHQ-12 and EAT-26) remained unchanged (10.3 ±4.3 vs. 8.9±3.8 and 14.8±9.6 vs. 11.0±5.6, P>0.05, respectively). This approach represents a marked difference from jockeys' habitual weight-making that largely involves dehydration and food deprivation. [ABSTRACT FROM AUTHOR]