Aim: Maintaining in-range glucose on days with PA is challenging for youth with T1D, often requiring fine-tuning of diet and insulin. We examined how PA and macronutrient intake impact glycemic outcomes in youth with T1D.

Methods: Youth and parents completed 3-day PA and diet records and youth wore 3-day masked CGM (iPro) every 3 months for 18 months. Days were classified as active (≥60 min PA) or inactive. Diet data were analyzed using Nutrition Data System for Research (NDSR) . Daytime (6 AM-11:59 PM) CGM glucometrics were: % time (T) in range (TIR) 70-180 mg/dL, %T<70, %T>180, and glucose CV. Analyses included complete days for PA, diet, and CGM data. Separate longitudinal mixed models for daily carb, fat, and protein intake (adjusted for age, T1D duration, sex, pump vs. MDI) , assessed changes in glucometrics on active vs. inactive days.

Results: Youth (N=136, 49% male, 73% pump users) were ages 8-17 yrs (12.9±2.6) with T1D duration 6.0±3.1 yrs and daily insulin 0.9±0.3 U/kg. At baseline, A1c was 8.0±0.9%, daytime %TIR 50±22% (12.0 hrs) , %T<70 5±8% (1.2 hrs) , %T>180 44±25% (10.6 hrs) , CV 37±11%; macronutrient intake was 49±9% carb, 35±8% fat, 16±4% protein. In all models of macronutrient intakes, %TIR increased by ∼5.3% (76 min; p=.01) with pump use; by 2.8% (40 min; p=.02) on active days; by 1.4% (20 min; p=.03) with 10% increase in carb intake; and by 1.7% (24 min; p=.02) with 10% decrease in fat intake. PA and carb intake did not impact %T<70; %T<70 decreased by 0.6% (9 min; p=.03) with 10% increase in fat intake. PA did not impact %T>180; %T>180 decreased by ∼5.6% (81 min; p=.02) with pump use; by 1.7% (24 min; p=.02) with 10% increase in CHO intake; and by 2.2% (32 min; p=.01) with 10% decrease in fat intake. CV decreased by 1.3% on inactive days (p=.04) ; by 1.1% with 10% decrease in CHO intake (p<.01) ; and by 1.3% with 10% increase in fat intake (p<.01) .

Conclusion: PA and macronutrient intake have varying effects on glycemic outcomes. The findings reinforce the need to tailor insulin dosing algorithms for diet and PA.


R.O.La banca: None. L.K.Volkening: None. E.Dassau: Employee; Eli Lilly and Company, Research Support; Dexcom, Inc., JDRF, National Institute of Diabetes and Digestive and Kidney Diseases, Stock/Shareholder; Eli Lilly and Company. S.N.Mehta: None. L.M.Laffel: Advisory Panel; Medtronic, Roche Diabetes Care, Consultant; Boehringer Ingelheim International GmbH, Dexcom, Inc., Dompé, Insulet Corporation, Janssen Pharmaceuticals, Inc., Lilly Diabetes, Novo Nordisk, Provention Bio, Inc.


National Institutes of Health (K12DK094721, P30DK036836) ; Iacocca Foundation

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