Impact of energy turnover on the regulation of glucose homeostasis in healthy subjects

Abstract

Objective: Sedentary lifestyle increases the risk of type 2 diabetes. The aim of this study was to investigate the impact of different levels of energy turnover (ET; low, medium, and high level of physical activity and the corresponding energy intake) on glucose metabolism at zero energy balance, caloric restriction, and overfeeding.

Methods: Sixteen healthy individuals (13 men, 3 women, 25.1 ± 3.9 years, BMI 24.0 ± 3.2 kg/m²) participated in a randomized crossover intervention under metabolic ward conditions. Subjects passed 3 × 3 intervention days. Three levels of physical activity (PAL: low 1.3, medium 1.6, and high 1.8 achieved by walking at 4 km/h for 0, 3 × 55, or 3 × 110 min) were compared under three levels of energy balance (zero energy balance (EB): 100% of energy requirement (Ereq); caloric restriction (CR): 75% Ereq, and overfeeding (OF): 125% Ereq). Continuous interstitial glucose monitoring, C-peptide excretion, and HOMA-IR, as well as postprandial glucose and insulin were measured.

Results: Daylong glycemia and insulin secretion did not increase with higher ET at all conditions of energy balance (EB, CR, and OF), despite a correspondingly higher CHO intake (Δ low vs. high ET: +86 to 135 g of CHO/d). At CR, daylong glycemia (p = 0.02) and insulin secretion (p = 0.04) were even reduced with high compared with low ET. HOMA-IR was impaired with OF and improved with CR, whereas ET had no effect on fasting insulin sensitivity. A higher ET led to lower postprandial glucose and insulin levels under conditions of CR and OF.

Conclusion: Low-intensity physical activity can significantly improve postprandial glycemic response of healthy individuals, independent of energy balance.

Fig. 1

Schematic study protocol. *randomized order

Fig. 2

Comparison between the different levels of ET (low, medium, and high) at different energy balances. a Eighteen-hour iAUCs_CGM [mg/dl], n = 16; b C-peptide excretions [µg/d], n = 15; values are means ± SDs; linear mixed model with multiple contrast tests, *p < 0.05 for comparison of ETs; CR caloric restriction, EB energy balance, OF overfeeding, med medium, ET energy turnover

Fig. 3

Comparison of differences in HOMA–IR (post- minus pre-intervention day) between ETs (low, med, and high) within different levels of energy balance (CR, EB, and OF). Values are means ± SDs; linear mixed model with multiple contrast tests; fasting insulin sensitivity was improved with CR and impaired with OF (all p < 0.01); n = 14–16; ET energy turnover, med medium, CR caloric restriction, EB energy balance, OF overfeeding

Fig. 4

Comparison of 2 h postprandial glucose (a–c) and insulin (d–f) iAUCs between the different levels of ET (low, medium, and high) and energy balance (CR, EB, OF) separated by breakfast, lunch, and dinner. Values are means ± SDs; linear mixed model with multiple contrast tests, *p < 0.05, **p < 0.01, and ***p < 0.001 for comparison of ETs; n = 16; ET energy turnover, med medium, CR caloric restriction, EB energy balance, OF overfeeding