Chrononutrition is a relatively new specialty in the field of nutrition and biology that seeks to understand how the timing of eating affects health. The central idea here is that metabolic health, heart health and body composition don’t just come down to what and how much we eat but also when we eat.
You surely know that our bodies work on almost 24-hour rhythms that are controlled by circadian clocks. The most obvious example is the sleep-wake cycle. Many other aspects of human biology are also controlled by 24-hour clocks operating in both the central nervous system and peripheral organs and tissues. ChronoNutrition seeks to answer two broad and related questions:
- How do the body’s natural clocks affect food choice and metabolism?
- How does meal timing affect circadian rhythms and, consequently, various health markers?
The latter is especially relevant for those who, like you probably, try to make food, movement and lifestyle decisions to maximize their health and longevity. Although the topic of chrononutrition has gained traction only within the last decade, evidence increasingly suggests we may be able to manipulate the timing of meals to improve well-being.
Today, I’ll briefly review the underlying premise of chrononutrition and return to a question that has come up many times in our community: Should I eat breakfast or not eat breakfast if my goal is optimal health now and for decades to come? should?
Here’s what you need to know to understand chrononutrition:
First, many biological functions are directed by central and peripheral clocks. I have already mentioned sleeping and waking up. Body temperature is another example. The body temperature peaks in the afternoon and decreases at night, touching its lowest point in the morning. More to the point of this post, many aspects of metabolism operate on circadian rhythms as well. it is included
- saliva production
- gastric emptying and intestinal motility (the movement of food through the digestive tract)
- release of digestive enzymes
- nutrient absorption
- beta cell function (insulin release from the pancreas)
- Glucose tolerance
Second, that elusive and elusive goal we call “health” depends on proper circadian rhythm alignment—everything happening when it should. Research shows, for example, that circadian misalignment, as caused by shift work and eating at the wrong times, leads to impaired immune function.
Third, we stay “on time,” partly thanks to behaviors that tell body clocks what time it is. These behaviors, such as sleeping at night and getting out in the sun early in the morning, are called zeitgebers. Eating at appropriate times is another zeitgeist that keeps our circadian rhythms aligned , contributing to physiologic homeostasis. Conversely, eating (or sleeping or receiving light exposure) at the wrong times causes misalignment and dysfunction.
The implication, then, is that we can use what we know about the body’s natural rhythms to figure out the best and worst times to eat, and the consequences of getting it wrong. That’s chrononutrition.
So what is the right and wrong time to eat?
There are some things scientists agree on, but I bet you’d be hard-pressed to find a scientist who thinks nighttime eating is healthy, or even health-neutral. All the evidence from shift workers, rats and human research subjects says eat during the day, don’t eat at night (actually, the reverse is true for rats as they are nocturnal, but the point still stands).
Although this is a very broad statement. We want to know more specifically, is it better to eat more calories in the morning, afternoon or evening? Should we load up on carbs (or protein or fat) at our first meal of the day or closer to bedtime? These are exactly the kinds of questions that chrononutrition researchers are investigating.
Epidemiological and observational data from prospective studies suggest that eating earlier in the day (i.e., eating breakfast) is associated with better glycemic control and less type 2 diabetes, better cardiovascular health, and less obesity (less body fat). Now, I know that many of you practice time-restricted eating and often skip breakfast. Before you get too worried, let me qualify this statement with a few big caveats.
First, let’s remember that observational studies cannot establish causation. These findings tell us nothing about whether eating or skipping breakfast leads to better or worse health outcomes, just that they may be correlated. Only randomized controlled trials can point to causality, and this is where these observations begin to break down. RCTs looking at weight loss and cardiometabolic risk, for example, have yielded conflicting results. And two recent meta-analyses of RCTs found no consistent association between eating versus skipping breakfast and body composition.
Furthermore, participants in these observational studies represent a cross-section of the population. By and large, they do not reflect the average health-conscious primal person fat-adapting and practicing intermittent fasting for the benefits . Quite the opposite. A new analysis of the large NHANES database linked skipping breakfast with a greater risk for cardiovascular disease-related mortality.
In this sample, people who skipped meals were more likely to smoke, drink excessively, have poor overall diet quality and experience food insecurity – all of which are independently associated with heart disease. The authors even go on to say that “skipping meals, especially skipping breakfast, may also be a behavioral marker for unhealthy dietary and lifestyle habits.”
In other words, breakfast skippers—meaning people who simply skip breakfast, not people who intentionally practice time-restricted eating—have higher risk factors overall than people who don’t. their breakfast-eating counterparts. How much, then, can we say that skipping breakfast is to blame for their poor health outcomes?
What does it mean to skip breakfast?
Should you skip breakfast or not? At this point, it’s hard to say for sure. It’s still early days for chrononutrition, and very soon breakfast will be crowned the most important meal of the day .
That said, the evidence is already fairly solid that humans are more insulin sensitive in the morning. People with insulin resistance and type 2 diabetes may have an easier time controlling blood sugar if they load more of their carbs, and perhaps more of their total calories, early in the day . Alternatively, if you’re going to consume more carbs in the afternoon, try to time them between workouts to take advantage of insulin-independent glucose uptake .
For everyone else, I’d say keep doing what feels right to you, but be open to experimenting. If you’re currently skipping breakfast and still struggling with high fasting blood sugar, poor energy during the day, or other stubborn health problems, it doesn’t hurt to try changing your eating window.
I’m open to the possibility that as more human studies proceed, we may find that the earlier eating window has some benefits for nearly everyone. Or we can learn that as long as you’re not eating too late, it doesn’t really matter whether you eat breakfast or not.
If skipping breakfast means your eating window is pushed back so you’re eating a large meal closer to bedtime, that could be a big problem.
Ultimately, the answer probably won’t be simple. The best and worst times for any given person to eat are almost certainly a function of genetic predisposition, lifestyle factors (what is most feasible and least stressful), personal preference, and existing health. And, I hope that meal timing and macronutrients will always be down the list of things to worry about, what and how much we eat.
Self-experimentation is still the best answer
If the epidemiological data is making you feel a little unsure about your breakfast-skipping ways, by all means go ahead and see what happens if you start eating breakfast. You’ll probably notice a big difference. Or you won’t, and you can start skipping breakfast if you want.
One caveat here is that research also suggests that consistent meal timing is important for circadian rhythm health. I wouldn’t recommend skipping breakfast one day, skipping dinner the next, and then eating from 8 a.m. to 8 p.m. the third day. Pick a schedule and stick to it for, say, a month (a time I chose arbitrarily). Then try another eating window for the same amount of time and compare.
See if you notice a difference in how you feel, look or perform in your workouts. Which one is easier for you given your work and family obligations? Importantly, has the quality of your sleep improved in one versus the other? You might also want to check blood markers and see how lipids or insulin (HbA1c) are affected.
If you feel and best skipping or having breakfast, this is your answer.
what is your n=1 data? Have any readers gotten good results from going back to eating breakfast after skipping periods? How about the opposite?
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