Background and aims
Time restricted eating (TRE) is a novel strategy to improve metabolic health by limiting the daily eating time window and consequently prolonging the overnight fast. This prolonged fast increases energy storage utilization and might improve insulin sensitivity due to an increased need to replenish nutrient storages. We performed an extensive investigation on the effects of TRE on glucose homeostasis and energy metabolism in individuals with type 2 diabetes.

Materials and methods
Fourteen volunteers with type 2 diabetes (BMI 30.5 ± 4.2 kg/m², HbA1c 7.6 ± 1.1 mmol/l) participated in a 3-week TRE arm (daily food intake within 10-hrs) and control arm (CON, spreading food intake over ≥ 14 hrs) in a randomized cross-over design. Insulin sensitivity (hyperinsulinemic euglycemic clamp),  24hr glucose (continuous glucose monitor) and 24hr energy metabolism (respiration chamber) was assessed at the end of both arms. Hepatic glycogen and lipid content as well as skeletal muscle mitochondrial function were also assessed.

Results
Time restricted eating improved time spent in normoglycemia (p = 0.005), and decreased fasting glucose (7.6 ± 1.3 vs 8.6 ± 1.5 mmol/l, p = 0.03) and 24hr glucose (6.8 ± 1.1 versus 7.6 ± 1.8 mmol/l, p < 0.001). Insulin sensitivity was unaffected by TRE (p = 0.25), but insulin induced non-oxidative glucose disposal (NOGD) increased with TRE vs CON (delta NOGD 4.3 ± 4.3 vs 1.5 ± 6.3 µmol/kg/min, p = 0.04). Twenty-four-hour energy expenditure was unaffected but 24hr glucose oxidation decreased with TRE (260.2 ± 28.4 vs 277.8 ± 38.7 g/day, p = 0.04). No effects were found on hepatic glycogen or mitochondrial function.

Conclusion
Three weeks of TRE improved 24hr glucose homeostasis in volunteers with type 2 diabetes. These effects could not be explained by improvements in hepatic or muscle metabolism.