Glucose Homeostasis Remains Normal in a Physically Active Military Population

INTRODUCTION: Glucose dysregulation is a significant obesity-related comorbidity known to impair both mental and physical performance. Glycated hemoglobin (HbA1c), a measure of average glucose regulation over 2-3 months, is elevated in over a third of American adults, indicating prediabetes (5.7-6.4%) or type 2 diabetes mellitus (≥ 6.5%). However, the 'fit-fat' concept suggests that physical activity may mitigate the adverse effects of adiposity on metabolic health. MATERIALS AND METHODS: This study investigated the relationship between relative body fat (%BF), HbA1c, and maximal oxygen uptake (V.O2max) as a surrogate measure of physical activity, in 216 physically active military personnel (188 men, 28 women). RESULTS: In men, fat mass (FM) was significantly, but weakly, inversely associated with HbA1c (β = -0.008, 95% CI [-0.015 to 0.000], SE = 0.004, P = 0.048), a finding that warrants further investigation. Maximal oxygen uptake was not significantly associated with HbA1c in either men or women. The variance explained by these models was low. Cluster analysis identified 3 distinct clusters with differing profiles of adiposity and fitness, but no significant differences in HbA1c were observed between them (F(2, 213) = 0.72, P = 0.488). CONCLUSIONS: In this physically active military population, normal mean HbA1c levels (5.2%) suggest that regular physical activity may mitigate the adverse effects of adiposity on glucose homeostasis. These findings support the 'fit-fat' concept and suggest that current fitness standards may be sufficient to maintain metabolic health. Therefore, inclusion of HbA1c testing in annual physical readiness standards may not be warranted in young, physically active service members.