BMI (35-39.9 kg/m2) is associated with a significantly lower risk of cardiovascular morbidity compared with a normal BMI

Objective: Obesity has been considered as a major risk factor for coronary heart disease (CHD), but the association between CHD and the degree of obesity is unclear. The objective of this study is to explore these relationships. Methods A total of 8299 patients from Xinjiang, China were enrolled in this study. BMI was categorized as normal (18.5–24.9 kg/m2), overweight (25.0–29.9 kg/m2), obesity class I (30.0–34.9 kg/m2), class II (35.0–39.9 kg/m2) and class III (≥ 40 kg/m2). We used logistic regression models to investigate differences in CHD risk between BMI categories and performed subgroup analysis in post-menopausal women. Results In this study, 62.1% of patients were overweight or obese, and only 37.9% had normal BMI. Logistic regression analysis showed that age [OR = 1.04, 95%CI (1.04–1.05), P < 0.01], and diabetes Yes vs. No [OR = 2.27, 95%CI (1.88–2.74), P < 0.01] might be independent predictors of CHD. Alcohol consumption Yes vs. No [OR = 0.70, 95%CI (0.56–0.88), P < 0.01] may decrease the risk of CHD. Lower risk was found in the obesity class II (BMI 35.0–39.9 kg/m2) group [OR = 0.62, 95%CI (0.41–0.93), P = 0.02] compare to people with normal weight. Postmenopausal women with a BMI of 35.0–39.9 kg/m2 also had a lower risk for CHD compared to women with normal weight. Conclusion We found that individuals with lower BMI might not necessarily have a lower risk for CHD, obese individuals with BMI between 35-39.9 kg/m2 might have a lower CHD risk compared to individuals who are of normal weight. Obesity evaluation and CHD risk prediction should require a more comprehensive assessment.