LucasT, I would love to see you expand on your thoughts, and lead us to references. Great learning experience !
I will!
I would like to watch the relevant podcasts first and I have more time in the weekend, so I will update it then!
LucasT:
I agree with you on the feeding window. It is interesting to look into but at the end of the day, I agree that we have to nail down what all is happening under the umbrella term "fasting". On the coffee thing... sorry, I just can't make that happen in my life.
At the end of the day, you have to make it fit with your lifestyle. Keeping your window early might optimize the effects, but is not doable for a lot of people, myself included because my social life does not happen in the mornings.
By the way, thanks for the new term "zeitgebers"... had to look that one up. haha
Well Im obviously biased towards coffee as Im addicted to it
Im really skeptical that, all things considered, it makes such a big impact (morning vs. evening). Specially if your control is ad libitum. I have yet to see (hopefully someone is trying this) any study comparing TRF in the evening vs. morning. From Panda's research, I think this paper is relevant to its application and findings:
A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits
A couple of quotes and findings from it (my comments in red):
"The median daily eating duration was 14 hr 45 min, and only 9.7% of the subjects had a daily eating duration <12 hr (Figure 4F) long. The weak correlation (r2 = 0.017) between the eating duration and BMI could be due to the limited sample size, the heterogeneity of the participants in terms of gender and age, and the fact that the eating pattern recorded in the monitoring period is a short-term snapshot of a person’s long-term diet-related behaviors."
So there was no relationship between eating duration and BMI.
"We tested if reducing the eating duration and metabolic jetlag associated with weekday/weekend differences in a subset of individuals would lead to reduction in body weight. We recruited 8 individuals with >14 hr eating duration for a 16-week pilot intervention study, such that each individual’s own baseline data served as the control (Figure 5A) condition."
"Because in rodents a daily eating period of up to 12 hr improves metabolic fitness (Chaix et al., 2014), the participants were requested to reduce their caloric-containing eating duration to a self-selected window of 10–12 hr and to consistently follow this duration during both weekdays and weekends so that the metabolic jetlag could be minimized. No overt suggestion concerning nutrition quality, quantity, or caloric content was provided. The individuals continued logging their food pictures using the same app as used in the baseline period for the next 16 weeks and also received a weekly summary of their feedograms and daily eating duration."
So he tested TRF in people with a long fasting window. Importantly, they also reduced social jetlag, so you have that the real intervention was:
- Reduce eating window to 10-12 hours
- Keep window constant (this is key)
What happened?
"All subjects reduced their eating duration (average reduction: 4 hr 35 min; 95% CI: 3 hr 30 min–5 hr 40 min; p < 0.001), and their weekday/weekend metabolic jetlag was also reduced to <1 hr (Figures 5B and 5C). The participants showed a reduction in total body weight (average loss 3.27 kg; 95% CI: 0.9081–5.624 kg) and, accordingly, excess body weight (Figures 5D and 5E, Table S3) and BMI (average reduction 1.15 kg/m2; 95% CI: 0.3247–1.980 kg/m2). In a subjective self-assessment of sleep satisfaction, hunger at bedtime, and energy level (in the mornings, and overall over the past few days), statistically significant improvement was observed (Figure 5F). All participants voluntarily expressed an interest in continuing unsupervised with the 10–11 hr time-restricted eating regimen after the conclusion of the 16-week supervised intervention. After 36 weeks (1 year since the intervention began), the participants maintained weight loss and sleep improvement and felt more energetic (Figures 5D–5F, Table S3)."
It worked! However...
"Although the participants were not overtly asked to change nutrition quality or quantity, reducing the eating duration led to reduced estimated caloric intake. Unlike mice, where reducing the eating duration to ∼10 hr does not alter total caloric intake (Hatori et al., 2012), our human intervention cohort reduced the estimated daily caloric intake (average reduction 20.26%; 95% CI 4.92%–35.6%; paired t test p < 0.05)."
So reduced eating window = reduced caloric intake. If you reduce on average 20% calories per day, you should get the seen results. What is nice is that, similar to low-carbohydrate diets, caloric restriction was spontaneous. But to conclude anything from this is that, again, calorie restriction works.
"Nevertheless, if time restriction under free-living condition inadvertently leads to caloric reduction, TRF as a method to reduce caloric intake is a more attractive option, as individuals, caregivers, case managers, physicians, and scientists do not have to adopt expensive and laborious methods to accurately track caloric count. Hence, irrespective of mechanism, time restriction offers an effective approach to improve health."
Hopefully we get soon new research in this area.
More food for thought:
Timed high-fat diet resets circadian metabolism and prevents obesity
"To examine the effect of timed HF feeding (RF-HF) on circadian metabolism and obesity, mice were fed regular chow for 4 h every day at the same time for 18 wk and were compared with mice fed a timed LF diet (RF-LF) and mice fed an HF diet AL (AL-HF)."
"The RF group was given food between zeitgeber time 4 and 8 (zeitgeber time 0 is the time of lights on)." [Mice night = lights on; so they feed the mice in an extreme late night eating equivalent to humans]
"Compared with mice fed the HF diet ad libitum, the timed HF diet restored the expression phase of the clock genes Clock and Cry1 and phase-advanced Per1, Per2, Cry2, Bmal1, Rorα, and Rev-erbα. Although timed HF-diet-fed mice consumed the same amount of calories as ad libitum low-fat diet-fed mice, they showed 12% reduced body weight, 21% reduced cholesterol levels, and 1.4-fold increased insulin sensitivity. Compared with the HF diet ad libitum, the timed HF diet led to 18% lower body weight, 30% decreased cholesterol levels, 10% reduced TNF-α levels, and 3.7-fold improved insulin sensitivity. Timed HF-diet-fed mice exhibited a better satiated and less stressed phenotype of 25% lower ghrelin and 53% lower corticosterone levels compared with mice fed the timed low-fat diet."
"Thus, timed feeding is dominant (18,–,20) and can rectify and/or advance the shifts induced by an HF diet. It was recently reported that mice fed an HF diet during the light phase gain significantly more weight than mice fed only during the dark period (27). Our results emphasize the importance of timed feeding of 4 h vs. food availability of 12 h. Indeed, we have recently shown the benefits in timed vs. ad libitum feeding (17)."
As mentioned here:
"Time-restricted feeding regimen improves CREB, mTOR, and AMPK pathway function and oscillations in expression of circadian core clock and output genes (Hatori et al., 2012 ; Sherman et al., 2012). It should be noted that both studies applied time-restricted high-fat diet, yet at complete different times throughout the day. The former limited the food availability to 8 hr during the dark phase, whereas, in the latter, food was provided for 4 hr during the light phase. Thus, it is conceivable that the key factor is the time restriction from food per se, rather than its occurrence at a specific circadian time."
"Conceivably, time-restricted feeding generates sharp feeding-fasting cycles, which consolidate circadian rhythmicity in gene expression and circadian activation of various metabolic pathways. This is because clocks in most peripheral organs readily respond to feeding cycles, and feeding time can shift their phase. Upon several days of time-restricted feeding, food availability and the endogenous clocks are aligned, irrespectively on whether the food is provided during the dark or the light phase. Hence, high-fat diet disrupts circadian rhythmicity through dampening of feeding-fasting cycles that serve as an extremely potent zeitgeber for peripheral clocks."
I think that most evidence points towards TRF during the active phase. If you work until 7-8pm and are still moving, doing things, etc, is a different scenario than someone who works until 4pm and can then rest. This is specially important given that we are bombarded with light of different wavelengths and other cues after 6pm (I dont know anyone who is in complete darkness or not exposed to some amount of light after 6pm. Additionally, most people still move around and are active until later in the evening).
Finally, if you weight train, this completely changes everything. As most people should weight train, the importance of eating during a specific period of the active phase vs. the importance of a feeding-fasting cycle is greatly reduced.
Might edit later