Meal Timing Crucial for Fat Loss? Is WHEN You Eat More Important for Losing Weight Than HOW MUCH You Eat?

In rodents, incorrect meal timing can partly override the benefits of energy restriction.

"You need a caloric deficit to lose weight..." The latest study from the University of Texas Southwestern Medical Center does not refute this principle. It does, however, add to it an "... and you must not eat at the wrong times!"

Confused? Alright, here's the elevator's pitch for the latest paper in Cell Metabolism: Scientists fed rodents calorie-reduced diets. Rodents lost weight, but only if they were fed at night (when they would usually be active), a pair-fed group that ate during the day (when mice are usually inactive), on the other hand, didn't lose a gram.
Ok, now that I probably have you full, unfettered attention (I know it's just a rodent study, but alas), let's take a closer look at the study design, its outcomes and whether the authors are right when they say (from the press release):

"Translated into human behavior, these studies suggest that dieting will only be effective if calories are consumed during the daytime when we are awake and active. They further suggest that eating at the wrong time at night will not lead to weight loss even when dieting [here: reducing your energy intake significantly]" (press release).

The study used a new automated feeder system which "enables long-term control and measurement of food access" (Acosta-Rodriguez 2017).

The study used a newly developed automated feeding system

Figure 1: Graphical summary of the study design (Acosta-Rodriguez 2017) | Acosta-Rodrı´guez et al. developed an automated feeding system that controls amount, duration, and timing of food availability and also records feeding and voluntary wheel-running activity in mice.

The feeder system was fully programmable and is integrated with wheel-running cages. It dispenses a single 300 mg precision-sized food pellet, and measurement of food consumption can be achieved by counting the number of pellets taken.

Feeders hold food in a hopper that dispenses one pellet into a chute for presentation to the mouse.  A successful delivery is confirmed by the consecutive activation of two sensors located underneath the hopper (drop sensor) and on the cage top (chute sensor). Once the mouse takes the pellet, the absence of food is sensed, and the removal time is recorded and displayed by the software in real time.

A new pellet is then dispensed into the cage top food bin. There is a programmable 10 min delay imposed between the last pellet taken and the next drop.
This delay, or rather, the length of it has been chosen, because previous experiments show that this is the time it takes for mice to be "discourage[d] from rapidly removing pellets and hoarding them" (Acosta-Rodriguez 2017). Together with the wheel-running data that was likewise recorded, the feeder system provided the basic data set for the study - data from five different feeding paradigms:

• 24 hr ad libitum food access (AL); 
• temporal restriction for 12 hr during the night (TR-night);
• temporal restriction for 12 hr during the day (TR-day); 
• 30% caloric restriction with 24 hr access starting at the beginning of the night (CR-night); or 
• 30% caloric restriction with 24 hr access starting at the beginning of the day (CR-day)

Just a brief reminder: For the nocturnal animals, all "-day" paradigms constitute 'eating against their biological clock'. Accordingly, it is at best mildly surprising that the mice's activity patterns did not change significantly, i.e. "even when eating exclusively during the daytime, TRday-fed mice remained active during the night resulting in wheel-running and feeding behaviors in complete antiphase to one another" (Acosta-Rodriguez | see Figure 2).

Figure 2: If the mice were fed at daytime, their feeding and activity cycles were no longer in sync (Acosta-Rodriguez 2017).

As you can see Figure 2 (bottom), the way the mice ate changed significantly, as well. Just as it has been observed in obese individuals who starved themselves all day (again: for mice that's starving all night), they started their feeding window with a binge - eating five pellets (~1.5 g, 5 kcal) within the first hour.

Figure 3: Energy intake (in #pellets, A) and daytime and 24h activity (% of baseline, B/C | Acosta-Rodriguez 2017).

In that, it may initially seem counter-intuitive, but the rodents total energy intake on the "mismatch" diet, i.e. TR-day, declined in spite of the initial binge (from 14.2 to 12.2 pallets, i.e. by  15%). If you think about it, though, this is something you may have observed in many obese individuals, too. At least according to their food logs many of them eat little enough to lose weight. By doing that "at the wrong time", however, they stagnate or even gain weight.
I guess you won't be surprised to hear that the TR-day mice were fatter than their peers. After all, they were allowed to consume as much chow as they wanted at the wrong time of the day. What is quite astonishing, however, is that there was a similar effect in the calorically restricted group of mice (CR-night vs. CR-day). Both groups consumed the exact same 11 pellets per day.

Figure 4: Summary of the most important results with respect to weight loss.

As stated in my graphical summary of the study results in Figure 4, only one of the groups lost weight, though, the mice who ate in sync with their activity pattern (and other aspects of their circadian rhythm | see Figure 4, graph). The mismatch between feeding and activity in the CR-day group, on the other hand, blunted the effect of the 21% reduction in energy intake (compared to baseline).
If we assume the same thing happens in man, we arrive at the previously proposed revised version of "You need a caloric deficit to lose weight...", i.e. "You need a caloric deficit to lose weight, and you must not eat at the wrong times!"

Figure 5: The reductions in average 24h-glucose seem to depend (largely) on energy intake and fasting times. Accordingly, reductions have been observed in the voluntarily restricting TR-day group, the CR-groups, and the alternative day group.

What is intriguing, though, is that the average glucose concentration, measured at four time-points for each mouse, are lower for the desynchronized groups (and the alternate day fasting group | AD). In view of the fact that the TR-day group consumed less energy, it is yet likely that - at least the unexpected glucose decrease in this group - could be explained simply by the reduced energy intake, which has previously been shown to account for reductions in blood glucose metabolism (Mendoza 2005; Speakman 2011); or, as the authors have it:

"the levels of blood glucose correlate with food intake, and since TR-day mice consume less food, they cluster with the caloric-restricted groups" (Acosta-Rodriguez 2017).

The improvements in the AD = alternative day fasting group, on the other hand, are probably a result of the extended fasting periods - despite caloric compensation on the non-fasting days and weight-yoyo from one day to the other (94.84% versus 103.7%  compared to ad-lib. diet). Future study will have to run more comprehensive panels to elucidate the interplay with insulin, glucagon, and glucocorticoids.

In spite of the tons of data, two important quantities  haven't been measured

No significant effects were observed for (absolute) liver weight, the binging mice in the CR group that consumed all their food in 2.5h had larger stomachs, though. On the other hand, the calorie restricted mice also had the lowest amount eWAT, i.e. (visceral) epididymal White Adipose Tissue - that's impressive because the CR-day mice didn't lose weight.

Unfortunately, the study didn't measure the effects on the rodents total lean or fat mass. Accordingly, we can not determine whether the scientists' hypothesis that this difference was mediated by compensatory increases in fat stores in other tissues cannot be (in-)validated. This is a major shortcoming of the study because even if it doesn't seem to be likely, there could be a selective improvement of the body composition in the CR-day group - with reductions in visceral fat and possible increases in lean mass. As I said, this is very unlikely, but even a redistribution from visceral to subcutaneous fat that would likewise explain the lack of weight loss may be considered a "health benefit" - bodybuilders would love it, too :-)
If this of the aforementioned possible counter-intuitive health benefit exists and, even more importantly, whether the general effect of meal timing is in fact "critical", will have to be elucidated in follow-up studies. Follow-up studies of which I'd obviously prefer them to be in man, as well. The problem is: As the authors of the study at hand pointed out, even previous rodent studies failed to fully control food intake and physical activity ... plus: even if you had the money for a human study in a metabolic ward, you will be hard-pressed to find 100% compliant subjects who are willing to stay there for 4-8 weeks while exercising fasted and eating in the midst of the night.

We can find support for the notion that the notion that circadian mismatches mess with one's energy balance in observational studies, though. Studies from shift-workers show...

• 20% increased obesity rates (Di Lorenzo 2003), 
• 10% higher risk of metabolic syndrome (metSyn) in healthy (Guo 2015), 
• 360-1170% increased risk of metSyn in people with at least one risk factor (Lin 2009)
• 101% increased risk of type II diabetes (Morikawa 2005),
• progressively increasing risk with the number of years spent on shift work (Pan 2011),

and a lot of other other things that would support that meal timing is "crucial", because these differences were often measured in the absence of differences in energy intakes (Atkinson 2008) or in the presence of reductions in energy intake (Ohtsuka 2001), which support the importance of time or, rather, a general circadian mismatch over a lack of activity and/or excess food intake that will skew the energy balance. With that being said, the previously referenced studies all lack the dietary control that would be necessary to make sure that the effects were not mediated by (random examples) increased snacking (Lennernas 1994&1995), or the consumption of unhealthier meals, a lack of chances to go to the gym, social obligations for attending meals, etc.

Figure 6: If you look at the complicity of the confounding factors of energy intake and use in shift workers, you realize why perfect control (which is absent in the existing human trials) is so important (Atkinson 2008).

As the figure from Atkison 2008 indicates, you can expand the list of potential confounders almost endlessly. Accordingly, the real-world value of studies in shift workers wrt general effects of eating "at the wrong time" is relatively low. After getting the usual "wake me up when this is a human study" comments, I think it's still worth mentioning the correlations with metabolic diseases in shift workers in this expansion of the initially published article.
References:

• Acosta-Rodríguez, Victoria A., et al. "Mice under Caloric Restriction Self-Impose a Temporal Restriction of Food Intake as Revealed by an Automated Feeder System." Cell Metabolism 26.1 (2017): 267-277.
• Almoosawi, S., et al. "Chrono-nutrition: a review of current evidence from observational studies on global trends in time-of-day of energy intake and its association with obesity." Proceedings of the Nutrition Society 75.4 (2016): 487-500.
• Anson, R. Michael, et al. "Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake." Proceedings of the National Academy of Sciences 100.10 (2003): 6216-6220.
• Atkinson, Greg, et al. "Exercise, energy balance and the shift worker." Sports Medicine 38.8 (2008): 671-685.
• Di Lorenzo, L., et al. "Effect of shift work on body mass index: results of a study performed in 319 glucose-tolerant men working in a Southern Italian industry." International journal of obesity 27.11 (2003): 1353.
• Guo, Yanjun, et al. "Shift work and the relationship with metabolic syndrome in Chinese aged workers." PLoS One 10.3 (2015): e0120632.
• Lennernas, M., et al. "The 24 hour intake of energy and nutrients in 3 shift workers." Ecol Food Nutr 32.3/4 (1994): 157-65.
• Lennernäs, Maria, Leif Hambraeus, and Torbjörn Åkerstedt. "Shift related dietary intake in day and shift workers." Appetite 25.3 (1995): 253-266.
• Mendoza, Jorge, et al. "Feeding cues alter clock gene oscillations and photic responses in the suprachiasmatic nuclei of mice exposed to a light/dark cycle." Journal of Neuroscience 25.6 (2005): 1514-1522.
• Morikawa, Yuko, et al. "Shift work and the risk of diabetes mellitus among Japanese male factory workers." Scandinavian journal of work, environment & health (2005): 179-183.
• Ohtsuka, N. Sudo, R. "Nutrient intake among female shift workers in a computer factory in Japan." International journal of food sciences and nutrition 52.4 (2001): 367-378.
• Lin, Yu-Cheng, Tun-Jen Hsiao, and Pau-Chung Chen. "Persistent rotating shift-work exposure accelerates development of metabolic syndrome among middle-aged female employees: a five-year follow-up." Chronobiology international 26.4 (2009): 740-755.
• Pan, An, et al. "Rotating night shift work and risk of type 2 diabetes: two prospective cohort studies in women." PLoS medicine 8.12 (2011): e1001141.
• Speakman, John R., and Sharon E. Mitchell. "Caloric restriction." Molecular aspects of medicine 32.3 (2011): 159-221.