BACKGROUND: Obesity and allergic diseases have increased dramatically in recent decades. Although adiposity has been associated with asthma, associations with allergic sensitization have been inconsistent. OBJECTIVE: To examine the association of adiposity and lipid profiles with allergic sensitization. METHODS: This study included 1187 rural Chinese twins (653 men) age 18 to 39 years, with skin prick tests, anthropometric and dual-energy x-ray absorptiometry-assessed adiposity measures, and lipid assessments. Allergic sensitization was defined as positive SPT to >/=1 allergen (9 foods and 5 aeroallergens tested). We applied sex-stratified generalized estimating equations to assess the association of adiposity and serum lipids with allergic sensitization, and structural equation models to estimate the genetic/environmental influences on any observed associations. RESULTS: Men had lower percent body fat (% BF) (13.9% vs. 28.8%) but higher rates of allergic sensitization (56.2% vs 36.7%) than women. Men in the highest %BF quartile were 2.1 times more likely to be sensitized than the lowest quartile (95% CI, 1.3-3.5; P trend = .003). In men, the risk of allergic sensitization increased with high-density lipoprotein (HDL) <40 mg/dL (odds ratio = 4.0; 95% CI, 1.8-9.2) and higher low-density lipoprotein quartiles (P trend = .007). This appeared to be partially explained by shared genetic factors between serum lipid levels and allergic sensitization. In females, lower HDL was associated with increased risk of allergic sensitization. CONCLUSION: In this relatively lean Chinese population, higher %BF, lower HDL and higher LDL were associated with greater risk of allergic sensitization, most notable in men. The observed associations among adiposity, serum lipids, and allergic sensitization in men appear to be partially explained by common genetic influences on these traits.