Have you noticed that despite exhausting attempts at cleaning up your diet, you still feel a little out of tune? It might be that you are ignoring an important 24-hour biological clock called circadian rhythm. The suprachiasmatic nucleus (SCN), found in the hypothalamus of your brain, acts as a master clock whose timetable synchronizes nearly every organ and tissue in the body with cues from sunlight. Now, take this natural phenomenon and couple it with another innate behaviour, food consumption. You might be surprised by the intricate circuitry between your gastrointestinal (GI) function and circadian regulation. The westernized schedule of 3 meals a day with dispersed snacks often ignores the body’s master clock and overlaps with the gut’s prearranged rest periods.
What if, similar to scheduling a shift, you can schedule yourself a shorter eating window based on your biological clock? A diet regimen named “time-restricted eating” (TRE) applies this exact routine, and working within its confines might grant you a new lease on life and get you back into synchronicity.
Gut-brain axis
The gut and brain are physically and biochemically linked by millions of nerves and neurons. We deem this network the gut-brain axis. The trillions of beneficial microorganisms in your GI tract, collectively known as the gut microbiome, make essential chemicals involved in the gut-brain axis. From duodenum to colon, you also have numerous clock genes acting as messengers to the hypothalamic SCN, which further aid with accurate circadian timing. Together, this programmed feedback loop stimulates hunger, gut motility, and prepares GI-related hormones in anticipation for your next meal. Desynchronizing this network may cause you food malabsorption.
When should you place your eating window?
Since sunlight is your primary input for this feedback loop, the timing of your TRE window is another important consideration. To maintain synchronicity during TRE, it might be best to avoid the temptation to skip your breakfast. First of all, insulin, one of the daily oscillating hormones, is most effective at taking up glucose from the bloodstream at dawn. Late dinners, as an alternative to early breakfasts, can cause escalations in circulating blood glucose levels for unsafe durations. Plus, eating breakfast is associated with better nutrient intake and less risk of cardiovascular disease. Consuming common breakfast foods like fortified cereal, milk, and fruit increase the likelihood that you reach the recommended daily amounts of folate, calcium, vitamin C, and fiber. In other words, maybe try to adjust your schedule for an early breakfast and even earlier dinner. For instance, an approximate 10-hour window of 8am to 4pm would serve you well.
How long should I make my eating window?
Duration of the TRE window will also influence the degree to which you profit from its potential benefits. Beyond knowing the start time of your window, there is the matter of providing adequate “gut rest”. Fasting for 12 or more hours could improve your gut microbial diversity/richness, gut barrier function, immune and inflammatory response, and production of metabolites. Incredibly, each of these benefits have the ability to prevent metabolic syndrome, and ultimately decrease the prevalence of numerous diseases. They might even help to improve your cognition and mood. However, extend your eating window beyond 15 hours and you may start to run into metabolic problems and sleep disorders. Restrict the eating window to 6 hours or less and you may increase risk for nutrient deficiency and even gallstone formation in women. The sweet spot seems to be an 8-10-hour TRE window.
Notable studies for disease prevention
Matthew J. McAllister et al. (2020) discovered that an 8-hour TRE was associated with significantly improved markers for cardiometabolic health, including reduced body fat and blood pressure in physically active young men. Similarly, both men and women at risk of cardiovascular disease had significantly reduced low-density lipoproteins, blood glucose, and blood pressure after 12 weeks of 10-hour TRE intervention. More impressively, men at risk for type-2 diabetes saw post-meal glycemic responses improve by 36% following only one week of 9-hour TRE. So far, the prospect of TRE aiding in weight loss is not too promising, at least no more than caloric restriction. Although, 8-hour TRE did prove superior over a low-carbohydrate diet in reducing weight and abdominal visceral obesity following a 3-month intervention.
Is TRE attainable long-term?
At first glance, TRE can easily be dismissed as yet another fad diet, but it’s different from every other nutrition program thanks to one notable attribute: its sustainability. TRE is classically grouped with other intermittent fasting (IF) methods such as the weekly 24-hour fast or biweekly calorie reductions. However, the TRE protocol shouldn’t necessarily imply fasting. Being a slight adjustment to your schedule, if at all, there is a promising adherence rate. Additionally, compared to other IF interventions, TRE comes with less risk of adverse side effects. And even if mild side effects do transpire, such as nausea or headaches, they are likely to subside in just a few weeks, if not less.
Is it safe?
Ultimately, no one should take a cookie-cutter approach to nutrition goals. You may find this regimen problematic if under 18 years of age, pregnant, diabetic, or have other health concerns. That’s a unique discussion to be had with your primary health care provider. Moreover, there is no question that a consistent, nutritious and holistic diet is the prerequisite for any type of experimentation you might be subjecting your body to.
Despite the risks that come with any new routine, TRE is well worth consideration for those interested in improving their overall well-being. No matter your lifestyle, TRE might be a more straightforward and attainable path to restoring your gut health for increased longevity.
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