Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans.
Level 2 - randomized trial
Randomized crossover trial in humans
PubMed 31151228 · doi:10.3390/nu11061234
What was done
Eleven overweight adult participants were enrolled in a 4-day randomized crossover trial comparing early time-restricted feeding (eTRF; eating window 8 am to 2 pm) to a standard control eating schedule (eating window 8 am to 8 pm). Participants wore continuous glucose monitors, and blood samples were collected to measure circulating hormones, cardiometabolic risk factors, and whole-blood gene expression of circadian clock, autophagy, and longevity markers.
What was found
Compared to the control schedule, eTRF significantly lowered mean 24-hour glucose by 4 ± 1 mg/dl (p = 0.0003) and reduced glycemic excursions by 12 ± 3 mg/dl (p = 0.001). In the morning before breakfast, eTRF increased circulating ketones and cholesterol, alongside increased expression of SIRT1 and LC3A (all p < 0.04). In the evening, eTRF increased MTOR gene expression (p = 0.007) and showed a non-significant trend toward increased BDNF (p = 0.10). eTRF also significantly altered diurnal cortisol patterns and the expression of multiple circadian clock genes (p < 0.05).
Why it matters
This study provides early proof-of-concept in humans that condensing the daily feeding window to earlier hours can acutely improve 24-hour glycemic control and modulate molecular pathways tied to cellular maintenance and the circadian clock.
Limits
The study is limited by an extremely small sample size (n = 11) and a very short intervention duration (4 days), precluding conclusions about long-term efficacy or clinical outcomes. Gene expression was assessed only in whole blood cells rather than metabolic tissues like liver, muscle, or adipose. The sample was restricted to overweight adults, limiting generalizability to normal-weight or diabetic populations.
Cited by
- supports Eating earlier in the day is associated with better overall cardiometabolic health.