Meal & Nutrient Timing
Are there better times to eat and/or are there times it’s best to avoid eating? A few lines of evidence shed some light on this. First of all, we see quite clearly and consistently that eating at biological night is a bad idea. Postprandial metabolism is much worse when a meal is eaten during the night (à la shift workers) than during the day. It’s likely that meals eaten close to DLMO are not the best idea from a metabolic standpoint. And of course, the larger the calorie (and potentially carbohydrate) load of the meal, the more detrimental it is to eat during the biological night.

We also reliably see tissues are more insulin sensitive in the morning than at night, with a decrease in insulin sensitivity across the day. Beta-cell function is also better in the morning (the relevance here being that insulin is secreted from the beta-cells of the pancreas, and thus beta-cell function is an important component of healthy glycemic control); therefore, there are greater glucose excursions following carbohydrate ingestion in the evening compared to earlier in the day. This may suggest that avoiding large carbohydrate loads in the evening or close to DLMO would be a good idea. There are several caveats here, which I’ll get to in the relevant section later in this article.

Observational work (image below) has shown that individuals consuming more of their daily calories between 4 hours before DLMO and the onset of sleep had a higher percentage of body fat.

Energy (Calorie) Distribution
As per the McHill paper referenced earlier, it seems as though having a larger percentage of our daily calories late in the day (closer to sleep) could be a bad idea for body composition over time. Similarly, as I’ve already noted, it has been suggested that earlier in the day, we are physiologically better equipped to handle larger meals. Therefore, a reasonable hypothesis exists around the value of placing a higher proportion of our calories earlier in the day.

One of the most intriguing and often cited papers to suggest this to be of importance is a 2013 paper by Daniela Jakubowicz. In this study, the researchers compared the impacts of two diets, matched for calories and macronutrients, but that differed in the distribution of that intake. Both groups dieted on 1,400 kcal per day, eating 3 meals per day, with each meal (breakfast, lunch and dinner) being eaten at about the same time (within a 3-hour window) for all individuals. As for the distribution, participants were either assigned to what I’ll refer to as a “front-heavy” or “back-heavy” distribution. The front-heavy group had a large breakfast and small dinner, and the back-heavy group consumed a small breakfast and large dinner. Specifically:

Front-heavy: 700 kcal breakfast, 500 kcal lunch, 200 kcal dinner
Back-heavy: 200 kcal breakfast, 500 kcal lunch, 700 kcal dinner
In these calorie/macro matched conditions, a front-heavy distribution of a large breakfast and a small dinner led to significantly (both statistically & pragmatically) more weight loss (8.7 vs 3.6 kg) than a back-heavy distribution (small breakfast and large dinner). Now, I think it’s incredibly unlikely that such a large difference in body weight change between the groups could be explained solely through impacts of calorie distribution/timing on energy balance. There are almost certainly differences that could be assigned to accuracy of tracking, adherence, and behavior that weren’t captured in the study. This specific study didn’t provide participants with their meals (however, participants were provided with a specific meal plan). So it’s possible the reported intake wasn’t as accurate as we would hope. However, it does tell us that something is going on when the distribution of intake is changed, regardless of how much is physiological and how much is behavioral. Other notable differences included lower blood sugar excursions (lower glucose AUC) for the day as well as lower ghrelin (an appetite hormone) levels throughout the day for those front-loading their calories. So, there are differences in hunger, in blood glucose response, and body composition.

A pair of studies that came out of Marta Garaulet’s lab in Murcia, Spain also seem to support that a front-loaded distribution has benefits. First, a 2013 paper looked at the impact of when the largest meal of the day (which is lunch in a Mediterranean population like the one studied) is consumed. This was part of a 20-week weight loss intervention that included participants working with a dietitian, engaging in an exercise program, and also having behavioral change addressed. At the end of the study, they looked back at people’s logged food intake and split the participants into those that consumed their largest meal of the day before 3pm or after 3pm. Roughly half of the participants were before, and half were after. They saw that those who consumed their largest meal earlier (before 3pm) experienced greater weight loss across the trial and had less insulin resistance.

After seeing this difference, the same group did an intervention trial to actually assign people to an earlier or later calorie distribution. Again, it was focused on the time of the largest meal of the day (lunch). Over a two-week trial, they compared the effects of an early lunch (main meal eaten at 1:30pm) and a late lunch (main meal eaten at 4:30pm). They then gave the participants a test meal, testing their blood glucose response to the meal, and found that the early lunch resulted in a better postprandial glucose response.

Nutrient timing may not be all that important
So, what do we make of this?

Well, research studies aren’t perfect. And findings don’t always agree. So rather than duking it out on a study-by-study basis, I’ll bottom-line it for you.

Based on the current body of research, and PN’s experience with more than 30,000 clients, I’ve come to realize that nutrient timing isn’t particularly important for most people trying to look and feel better.

Let me be clear: no, I don’t think nutrient timing is dead, worthless, whatever. In certain situations it’s probably really important. (We’ll explore them below.)

However, lots of really smart and hard working people are getting lost in the finer points of nutrient timing, while consistently missing out on sleep, or vegetables, or other — more important — health and lifestyle factors. And that’s a shame.

So, that’s my bottom line. But, if you’re up for it, let’s go a little deeper.