8731 Glucose homeostasis remains normal across a range of adiposity in fit men and women

Abstract Disclosure: A.W. Potter: None. G.C. Chin: None. J.I. Jacques: None. L.J. Nindl: None. D.P. Looney: None. W.J. Tharion: None. C.L. Chapman: None. E.N. Halford: None. K.E. Friedl: None. Introduction. Glucose dysregulation is a major obesity-related comorbidity, affecting mental and physical performance. Glycated hemoglobin (HbA1c) is a validated and stable biomarker representing glucose regulation over 2-3 months. Nearly half of American adults (41%) have elevated HbA1c concentrations representing prediabetes (≥5.7%). In a large cross-sectional sampling of the American population, HbA1c becomes elevated in 33% of individuals at >24% body fat (BF) (men) and >38%BF (women). However, daily physical activity is an important moderator of metabolic health and adiposity - the “fit fat” concept. We evaluated this effect in physically active men and women. Methods. Body composition and metabolic health data were obtained from 36,392 adults (18,130 men and 18,262 women) in the National Health and Nutrition Examination Survey (NHANES) from 1999-2018, for comparison of %BF and HbA1c relationships. Body composition and HbA1c data were obtained from 220 healthy and physically fit active-duty military men and women (188 men, mean ± SD (range): age 25.7 ± 5.9 (18-53) years; height 176.3 ± 7.7 (154.0-201.1) cm; body mass 85.3 ± 11.9 (55.7-134.7) kg, maximal oxygen uptake (VO2max) 49.1 ± 11.9 (33.8-62.5) ml/kg/min; 32 women, age 26.5 ± 7.0 (19-45) years; height 161.4 ± 5.9 (147.1-172.8) cm; body mass 63.9 ± 8.3 (46.7-86.6) kg, VO2max 42.5 ± 8.3 (29.1-52.6) ml/kg/min). Body composition was measured using DXA (iDXA, General Electric Healthcare, Madison, WI) and HbA1c was measured from capillary blood samples using a validated point-of-care analyzer (DCA Vantage Analyzer, Siemens Medical Solutions USA, Inc, Malvern, PA). Results. HbA1c remained within the normal range (<5.7%) for 98% (216/220) of a relatively wide range of %BF in a group of men (9-36%) and women (21-46%) who engaged in daily physical activity. This sample included 64 men (34%) and 4 women (12.5%) that exceeded the 24 and 38%BF thresholds where clinically high HbA1c concentrations have been observed in the civilian population. From this subset, none of the assessed women had HbA1c ≥5.7%. Three men had HbA1c 5.7-5.8% and also high measured physical fitness (VO2max, 50.1-62.5 ml/kg/min) and low %BF (15-17%); while one had lower physical fitness (VO2max 43.87 ml/kg/min) and higher body fat (26%) (HbA1c 6%). Conclusion. Glucose homeostasis remains within normal values across a range of adiposity in fit men and women. These data support the importance of daily physical activity in mitigating elevations in HbA1c, even in individuals with increased relative body fat. Physical activity appears to have a protective effect for metabolism. Presentation: 6/3/2024