When and how often should you eat?
By Ari Snaevarsson, Features Editor
I think the question, “When/how often should I eat,” or some variation of that, is on a lot of people’s minds. I have quite a bit to get through in answering this, but I wanted this all in one succinct piece, so here it is. Bear with me and give this a read, because this should serve to put this worry to rest and give you the [almost] complete story.
The first aspect to this issue is the “when.” Put more plainly, should you consume more calories early in the day or later? The boring, but necessary, answer is that the studies are divided pretty evenly on this (about a 2:2:3 ratio, the third finding being that neither makes a difference).
So I will give the answer you were probably expecting: it boils down to personal preference. Are you hungrier in the mornings? Well then, sorry if I am blaspheming for any die-hard intermittent fasters out there, but skipping breakfast will probably not be your best bet.
Interestingly, when studies have participants change their habits in this realm, that is when results are reliably reproduced. This only serves to further validate the notion that dietary mindfulness/awareness is crucial to a successful dieting endeavor.
Then there is the more controversial question of meal frequency. The preeminent dietary advice used to be to eat frequent, small meals throughout the day. This was based off of a handful of animal trials and a few flawed human trials (look up the studies of nibbling versus gorging; they are actually quite interesting).
The physiological theory was that this would somehow “stoke the metabolic furnace” and enhance weight loss. Where the logic begins to fall apart is in its assumption that the act of eating marks some massive metabolic event. Actually, calories expended in chewing, digesting, absorbing, and transporting nutrients (called the thermic effect of food, or “TEF”) are trivial at best, and any postprandial hormonal responses that occur would just be smaller versions of the responses we would expect to see following consumption of larger meals.
With the growing popularity of intermittent fasting (IF), the broscience has shifted towards advocating for two or so larger meals a day, the benefit supposedly stemming from the omission of breakfast, to induce a roughly 16-hour fast. However, this too was the product of an inaccurate elaboration of study results. This was largely steeped in the premise that an intermittent fast represents how our ancient ancestors would have eaten. Unsure of when the next meal would come, hunter-gatherers would purportedly feast only once or twice a day.
The science behind this is backed up by the observed physiological response to fasting. As it stands, a series of important events occur during a fasted state. The liver is depleted of glycogen (which induces positive neural/hormonal changes in its own right), blood glucose eventually falls (improving insulin sensitivity), fatty acids are preferentially mobilized and oxidized, and voila, you lose fat!
Of course, to again be the bearer of bad news, the story is not so cut and dried. Most of these changes would not occur to a significant enough degree until we enter a prolonged fast (at around 72 hours or more, and other than proponents of “water fasts,” I would hazard to guess most would not find this approach feasible), and surely some would not occur at all until that time. Moreover, these are entirely theoretical in nature, as few, if any, of the available studies look at both surrogate endpoints (i.e. decreased blood glucose) and the clinical endpoints we are ultimately after (i.e. more weight lost).
Be skeptical of cited studies
Here is the blunt truth: most of the relevant studies are flawed. For example, the majority of IF studies people rely on to make claims of its benefits come from alternate day fasting (ADF) diets that had subjects eat ad libitum on feeding days. Now, I do not mean to imply we abandon all studies. Rather, this presses a point I tend to harp on in my articles and rants, namely that studies need to be used and understood strategically and in the appropriate context.
For example, large epidemiological studies looking at correlations without ascertaining a comprehensive profile of their subjects are not necessarily worthless. They serve the purpose of providing insight into large-scale trends, which can then be examined further in more tightly controlled trials. Most of the studies out there right now give that foundational basis for scientists to expound upon further in controlled study designs.
Gurus promoting a specific diet protocol for monetary gain will often cite studies ad nauseum. These should be met with heavy skepticism, as it only takes a brief look into one of these studies to see the story is not always as unequivocally one-dimensional as the guru might have you believe.
At the end of the day, I think the appropriate answer can be summed up as such: Make sure you have your ducks in a row before jumping into this variable. Starting from the most important, foundational level (this specific hierarchy of nutrition comes from the guys at Precision Nutrition), do you know how much you are eating each day? From there, how are you eating? Why are you eating? Then we can ask, what are you eating? And are you doing all of this consistently?
If you answered no or were unsure for any of these, that needs to be addressed before you can move forward. Even then, and I think it is fair to say this singles out only a few individuals (not to be misconstrued as a judgment call), you would be hard-pressed to note any significant, physiological benefits to an altering of your caloric distribution or meal frequency. As I have said, where this might have relevance is mainly in improving long-term adherence. For example, if you are hungriest at night, moving your food back towards night would be the obvious solution. Hopefully this was all informative. I left quite a bit out, but I will be sure to address some of the missing elements in future articles.