A study published yesterday showed that early time-restricted feeding(eTRF) for 4 days led to several metabolic improvements in overweight adults who were metabolically healthy. The study found that compared to eating from 8am-8pm, when doing subjects doing eTRF(8am-2pm) had:
- Decreased mean 24 hour blood glucose levels
- Decreased glucose spikes, especially at night(Duh)
- Increased ketones and SIRT1(An anti-aging gene) expression in the morning
- Increased expression of the autophagy gene LC3A in the morning
- Increased brain-derived neurotrophic factor(BDNF) at night
The study design was pretty tight, with subjects being exposed to either eTRE or the control diet, then washed out for 5 weeks and exposed to the other condition. The contents of the diet were identical under both conditions, and each arm of the study had only 3 meals, as shown below.
Blood glucose was recorded using a Dexcom G4 continuous glucose monitor. Below is a chart of the 24-hr CGM data for both arms of the study. Check out those huge blood glucose spikes after each meal in the control group; the eTRF group had a much more stable blood glucose which was elevated during the day and dropped during the night.
Overall this was a very cool study and suggests that there are metabolic benefits to when you eat independent of what you eat. The glucose data pretty much confirms what has been hypothesized: that insulin sensitivity is better in the morning and thus, carbs may be handled better in the morning.
Another finding of note was that in the control arm, glucose levels remained elevated after the last meal deep in to the sleep period. This is something to be avoided, IMO, and it would have been interesting to look at the subjects’ sleep data. There are some other interesting findings with regard to this, and I encourage you to check out the open access study linked above for those findings.
The eTRF arm also saw changes in the expression of several circadian clock genes. This likely played a role in the more robust cortisol rhythm in the eTRF condition: higher cortisol in the am, and lower cortisol in the pm. More or less a much better cortisol rhythm which would increase alertness in the morning and make it easier to fall asleep at night.
Finally, the finding that eTRF increased BDNF at night is very intriguing. BDNF is essentially Miracle-gro for neurons, increasing neuronal growth and the formation of connections between neurons. This data suggests that eTRF may have brain-sparing effects, brain- enhancing effects, or a combination of the 2. While increased autophagy and SIRT1 gene expression in the am are great to see, more data is needed to confirm that this led to increased gene activation and protein levels.
These results suggest that early time-restricted eating can cause some pretty robust metabolic changes in as few as 4 days. It’s important to understand that this was a very small study with only 11 subjects, so more investigation is necessary. Another thing to keep in mind is that this was a tightly controlled study and not necessarily representative of free-living conditions.
One thing that could be problematic is translating this data into something people can use. I’ve been implementing this stuff with people for over 2 years now, and have seen firsthand that most people simply won’t stick to a strict eating schedule or only consume 3 meals. In my opinion, this is indicative that other circadian exposures are off, altering mood, appetite, blood glucose regulation, and energy levels.
Universally, this can be corrected by addressing other circadian factors such as light exposure, physical activity, sleep hygiene, managing stress, and addressing metabolic dysfunction.
If you’re looking to figure out how to address these factors, look no further than my Circadian Retraining Program(Shameless plug free of charge), To learn more details about the program including who’s right for it, testimonials, what’s in the program, or to order, click here.