The Best Time to Eat, Train, and Think: According to Biology

This is going to be a VERY brief post about peak human performance. In one way or another, all of us are looking to optimize something — whether it be creativity, productivity, metabolic health, performance, or simply our day-to-day enjoyment of life.

While we all may prefer to do various activities at certain times of day, it turns out, biologically speaking, there IS a best time to engage in different types of cognitive and physical tasks, independent of when we may “feel like” doing them.

Much of this is related to our internal circadian rhythms — the ~24 hour clocks present in nearly all of our cells — that oscillate throughout the day. We have circadian rhythms in cardiovascular function, hormone release, body temperature, and brain function, among other physiological processes, and each of these peak and trough at different times through the ~24 hour day (I use the ~ because our biological day is just slightly longer than 24 hours.)

Timing the peaks of certain physiological processes with external activities such as eating, exercising, sleeping, and thinking is likely to produce the ideal situation for our biology, and also our productivity during all of these tasks.

Here is the evidence on when you should eat, train, and think.

EAT

Much of the (recent) evidence supports that the best time to eat is earlier in the day. This can mean consuming a majority of your daily calories earlier in the day or, if you take part in time-restricted feeding (TRF), shifting your eating window to occur earlier in the day rather than later. How to structure this is totally dependent on your preferences and schedule, but some studies find that having breakfast beginning at 8am and dinner ending at 3pm (I know, this sounds unfeasible) can produce some positive health outcomes compared to a feeding window that starts around 1pm and ends around 8pm. 

Breakfast like a king, lunch like a prince, dinner like a pauper (if at all.)

Circadian rhythms in energy metabolism: J Acad Nutr Diet. 2015 Aug; 115(8): 1203–1212.

If you want a more in-depth post on time-restricted feeding and the benefits of eating earlier, check out this post that I wrote on the subject: Early to Bed, Early to Dine: The Robust Health Benefits of Early Time Restricted Feeding (eTRF)

EXERCISE

I’ll begin this short diatribe with the disclaimer that independent of timing, exercise is beneficial and important (necessary) for optimal health. Exercise when you can. But, it is worthwhile to note that physical performance is highly dependent on time of day, and planning your exercise routine around these known peaks in performance could help you to run longer or lift heavier.

Due to variations in body temperature, muscle function, and certain hormones, peak power output, strength, VO2 max, and endurance all occur later on in the day — sometime around early to mid afternoon. Performance output, no matter how it’s measured, is better later in the day compared to earlier.

Side note: a recent study found that ingesting caffeine was able to normalize some of these morning-afternoon differences in performance.

However, in regards to certain metabolic outcomes, morning exercise may have particular benefits. This may have to do, in part, to the fact that much morning exercise takes place in the fasted state and therefore, may benefit fat-burning capacity and activate certain pathways that aren’t as stimulated when exercise takes place in the “fed” state.

Sato S, Basse AL, Schönke M, et al. Cell Metab. 2019;30(1):92–110.e4.

If you’re interested in reading more about exercise timing in relation to performance and metabolism, check out this article: Want the Most Benefit from Exercise? Timing is Everything

THINK

This is an interesting and less well-studied topic. When should you engage in cognitively demanding tasks? Mental alertness and cognitive performance may be more variable among individuals based on chronotype and preference rather than internal biological rhythms, per se.

However, myself (and others) find that peak alertness and focus can happen early in the morning or (very) late at night, perhaps due to the fact that outside distractions are reduced (or non-existent) at this time.

Some literature suggests that peak arousal and cognitive performance, since they’re so individual, are likely a function of one’s chronotype (day and night preference), internal rhythms, and subjective arousal. In essence, when you go to bed, when you wake up, your work schedule, and social and familial demands will all dictate the time you have to engage in cognitive tasks as well as the times that these tasks can occur. 

A suggestion here based on observation rather than evidence. If you need time for creativity, reading, writing, or deep thought, make sure this happens at a time when you feel most alert, external distractions are minimized, and when you’ll be able to engage in the task without interruption for a considerable period of time. 

Much of health and performance is all about making sure the “low hanging fruit” are taken care of — prioritizing basic nutrition, sleep, stress-reduction, etc. However, an area where I’m keen to explore is the space beyond the “low hanging fruit” — the space where we now try to optimize our physical and mental function by leveraging supplements, meal and exercise timing, and the nuances of sleep and wake schedules. In  this way, we can control our biology, rather than let our biology control us.

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