Early Time-restricted Feeding Regimen Improves Glycemic Variability, Time in Range in Patients with Prediabetes, Obesity

Intermittent fasting following an early time-restricted feeding (eTRF) schedule improved glycemic fluctuations and decreased time spent above target glycemic range among individuals with prediabetes and obesity, according to findings from a small study¹ presented yesterday at ENDO 2023, the Endocrine Society's annual meeting.

The observed increase in stability was achieved without accompanying weight loss, a common outcome while following the eTRF eating pattern, according to the study authors.

eTRF confines caloric intake to the first 6-8 hours of the day, authors explain. Previous research suggests improvements in cardiometabolic health among individuals following the approach. However, study investigators, from New York University NYU Langone Health in New York, state that it has not been clear from earlier studies whether the salutary effects are the result of the associated weight loss or of the metabolic effects of eTRF itself.

Bruno and colleagues conducted a randomized 7-day isocaloric supervised feeding study to compare the eTRF schedule, 80% of calories consumed before 1 pm, with a "usual" feeding schedule (control), 50% of calories taken in after 4 pm.

The study's 10 participants were randomly assigned in a 1:1 fashion to follow either the eTRF or usual feeding pattern for days 1 to 7. They were then crossed over to the alternate feeding arm for study days 8 to 14. The caloric value of food provided to all participants was calculated for weight maintenance so that Bruno and team could determine effects of the intervention independent of what might be observed from weight loss.

Glycemia was assessed over time using continuous glucose monitoring and participants took oral glucose tolerance tests (OGTT) at study baseline, at the day-7 crossover point, and on the last day (14) of the study.

According to the study abstract, following the eTRF schedule led to a decrease in mean amplitude of glycemic excursion (MAGE) of 2.5 mmol/L compared to a decrease of 2.9 mmol/L seen in the control arm (P<.05). Investigators also observed decreased time spent above target glycemic range of 3.1% vs 6.7 % (P=.02), respectively. Time spent in glycemic range was similar between the 2 groups, at 75.4% for eTRF and 74.9% for the control arm (P=.88).

When they calculated the area under the curve of OGTT for both groups, Bruno et al found no significant difference between them (eTRF 16391 vs control UFP 1586). Further the study authors reported that there were no fluctuations in participants' weight during the study.

“Our research shows that just one week of following this diet strategy reduces fluctuations in blood sugar levels and reduces the time that the blood sugar is elevated above normal levels,” Joanne Bruno, MD, PhD, an endocrinology fellow at NYU Langone Health in New York, said in a statement. “This suggests early time-restricted feeding may be a helpful strategy for those with prediabetes or obesity to keep their blood sugars in a normal range and prevent them from progressing to type 2 diabetes.”²

Signaling and metabolomic implications of the observed glycemic improvement are the subject of ongoing investigations, they note.¹

1. Nasserifar S, Bruno J, Vanegas S, et al. Early time restricted feeding as a weight neutral approach to improved glycemic variation. Abstract presented at ENDO 2023; June 15-18, 2023; Chicago, IL. Accessed June 16, 2023.

2. Early time-restricted feeding improves blood sugar levels. News release. Endocrine Society. June 14, 2023. Accessed June 16, 2023.