To determine if elevated plasma γ′-fibrinogen, typically involved in the formation of fibrinolysis-resistant clots, confers an increased risk for cardiovascular disease (CVD) and thrombosis in children as it does in adults. Although obesity-related hyperfibrinogenemia is frequently reported in children, the role of γ′ fibrinogen and its response to physical activity-based lifestyle are less clear in this population.

In a randomized controlled 3-month physical activity–based lifestyle intervention, γ′ fibrinogen concentration was measured in 21 children (aged 14-18 years; Tanner stage > IV), including 15 in the obese group and 6 in the normal weight group, with body mass index percentiles for age and sex of >95 and <85, respectively.

The relationships between γ′ fibrinogen and other risk factors for CVD, such as markers of insulin resistance and subclinical inflammation, along with body composition (as measured by dual-energy X-ray absortiometry), were assessed before and after the intervention. γ′ fibrinogen concentration was higher in the obese group compared with the normal weight group (P < .05) and was correlated with other risk factors for CVD (adjusted R² = 0.9; P < .05), and insulin emerged as the major predictor of γ′ fibrinogen. The intervention reduced γ′-fibrinogen concentration (P < .05).

Our data reveal: (1) elevated γ′ fibrinogen concentrations in obese insulin-resistant children compared with normal lean controls; (2) a relationship between γ′ fibrinogen and other CVD risk factors; and (3) physical activity–induced reduction in γ′ fibrinogen in obese children.