Background: Few studies have examined the underweight–morbidity relationship, and those that have were conducted in non-U.S. populations and limited in their evaluation of cardiovascular disease (CVD) risk factors.

Purpose: To examine the associations among underweight (along with overweight and obese) and various CVD risk factors in a national sample of U.S. adults (aged ≥20 years).

Methods: Ten years of data (1999–2010) from the National Health and Nutrition Examination Survey were used (analyzed in 2014). Underweight (tertiles); overweight (25–29.9); and obesity (three classes: 30–34.9, 35–39.9, and ≥40) were assessed from measured BMI. The evaluated biological and anthropometric markers included waist circumference; mean arterial pressure; C-reactive protein (CRP); fasting low-density lipoprotein (LDL) cholesterol; total cholesterol; fasting triglycerides; and fasting glucose.

Results: After adjustments, underweight adults had significantly (p<0.005) lower levels of CRP (β=–0.12, Tertile 2); total cholesterol (β=–17.7 and –12.2, Tertiles 1 and 3); total cholesterol to high-density lipoprotein cholesterol ratio (β=–0.39 and –0.46, Tertiles 2 and 3); LDL cholesterol (β=–20.7, Tertile 1); and triglycerides (β=–37.1 and –18.0, Tertiles 1 and 3) compared to normal-weight individuals. The severely underweight and obese were less likely to be physically active than normal-weight adults (p<0.001). Adults in each of the overweight and obese groups had higher levels for each biomarker compared to normal-weight individuals.

Conclusions: Underweight adults have lower (i.e., more favorable) levels of various CVD biomarkers.