Traditional nutrition advice includes statements such as “breakfast is the most important meal of the day,” and “as long as you don’t over-consume calories, it doesn’t matter when you eat”. Unfortunately, both of these long-standing beliefs are flawed. The latest iteration of the US Dietary Guidelines no longer explicitly encourages breakfast consumption, as the vast majority of the science supporting eating breakfast as a weight-management tool has been de-bunked. And it turns out that meal timing does have an impact on overall health.
A few weeks ago, a friend tweeted an article about the origins of breakfast cereal. According to the article, the vital importance of breakfast was espoused by Dr. John Harvey Kellogg to promote a new food and health panacea: corn flakes. After the invention of breakfast cereal, companies began producing and marketing their new cereal products as essential for health and productivity. Initial research into breakfast consumption was primarily done with observational studies, which did show that those who ate breakfast were generally healthier than those who did not. However, those studies have since been called into question and new research is proving that breakfast is certainly not necessary for weight management. Even the concept of jumpstarting your metabolism with breakfast is incorrect — researchers have discovered metabolic rate increases during fasting states. Upon waking in the morning, our bodies are in a fasted state and are burning stored glycogen and fat for fuel. This fasted state is an essential part of our natural metabolic rhythm. In fact, the better our metabolisms are at burning stored fat as fuel, the longer we can comfortably go without food. The problem many of us experience in the morning is that we aren’t very good at burning fat as fuel, so we wake up famished. A great way to get better at burning fat is to slowly and slightly extend our natural nightly fasts. When we do eventually break-the-fast, we should do so with high-quality, nutrient-dense foods, not sugar-laden breakfast cereals or other non-nutritious convenience foods we opt for because we’re in a hurry and “need” breakfast.
Now that we all realize we can survive without breakfast at 7am and that it isn’t going to destroy our metabolism, there are a few considerations to keep in mind regarding meal timing, the first relates to insulin sensitivity. We are most insulin sensitive in the morning and least sensitive at night. This means that we are better able to utilize sugars coming from carbohydrate in the morning and as the day progresses, our insulin sensitivity decreases — increasing the likelihood that carbohydrate intake will lead to unhealthfully high blood sugar levels and compensatory over-secretion of insulin. Consuming a normal composition (containing carbohydrate, protein, and fat) meal at night, raises insulin levels more than that same meal would if consumed in the morning. It is increasingly believed that weight gain and obesity are a direct result of chronically elevated insulin levels. Therefore, a key weight management strategy should be to obtain the bulk of calories from carbohydrates earlier in the day.
The second consideration regarding meal timing relates to our circadian rhythm. The human brain has a master circadian rhythm center called the suprachismatic nucleus (SCN). Our SCN is the master regulator of our sleep and wake cycles and is set by exposure to bright light. The SCN also interacts with peripheral oscillators of our circadian rhythm which are located in many organs (adrenals, liver, pancreas, stomach, esophagus, etc.). The peripheral oscillators function as clocks for those organs and help regulate many processes including the secretion of hormones, cellular repair and breakdown, and the management of metabolic wastes. These peripheral oscillator clocks are set by our intake of food and meal timing. The signaling pathways between the peripheral oscillators and the SCN exist to synch our search for food and our consumption and digestion processes with daylight — the time we are awake, and metabolic repair processes (which only happen during periods of fasting and rest) with darkness and sleep. So, although our master circadian rhythm is primarily driven by exposure to bright light, it is also strongly influenced by food intake and meal timing. Synching feasting and fasting with light and dark is metabolically beneficial. Since proper circadian rhythm is essential for healthy sleep, meal timing is also an important consideration for sleep optimization. Dr. Satchin Panda explained much of this information on an excellent video interview with Dr. Rhonda Patrick.
Dr. Panda has also conducted investigations on meal timing and health outcomes. His research on mice using a time-restricted feeding window demonstrated remarkable results. Depending on the trial group, mice were either allowed to consume food at-will, or feeding was restricted to a time window between 8-12 hours of the day. The mice in all groups had access to the same (relatively low-quality) diet. The mice who could eat at-will became obese, while the mice who could only eat for 8-12 hours of the day did not, despite having the same caloric intake. In fact, the mice who were fed on the attenuated 12 hour schedule, showed dramatic improvements in many health markers including:
- Decreased fat mass
- Increased lean muscle mass
- Decreased inflammation
- Improved glucose tolerance and insulin sensitivity
- Improved lipid profiles
Those fed on the 9 hour schedule also saw improvements in aerobic endurance capacity. All of the categories listed above have implications for many disease processes (alzheimer’s, diabetes, heart disease, obesity) and overall longevity. Although this research was done on mice, newer studies conducted on humans show meal-timing is an important determinant of health status. What I find most remarkable about this research is that there were dramatic health improvements without calorie restriction. This is the key differentiation between time-restricted feeding and many recently popularized intermittent fasting protocols, which either by design or default can result in 10-40% reductions in overall calorie consumption.
Based on all of the information above and the importance I place on longevity, sleep quality, and disease prevention, I’ve adopted a 10-12 on, 14-12 off eating pattern which promotes a healthy circadian rhythm and allows for daily metabolic rest, repair, and rejuvenation. This means I eat within a 10-12 hour window each day, generally starting between 8-10am and ending between 6-8pm. The meal pattern and nutrient composition of my diet varies depending on the signals I get from my body and my routines (exercise, sleep, etc.), but I generally eat three high-quality, nutrient-dense meals. The shift from my old not time-structured eating pattern to my current pattern took a couple of months. During that transition, I noticed my hunger between meals and overnight became less intense and my energy levels fluctuate less throughout the day. The antidotal explanation for this is that by slowly altering the timing of my meals, I gradually up-regulated the metabolic pathways necessary for burning fat as a fuel source, and down-regulated reliance on frequent meals and carbohydrates.
Although, the pattern I follow is similar to intermittent fasting, I prefer to use the term time-restricted eating. I make this distinction because this plan is not a fast — it doesn’t limit calories in any way, it simply narrows the window of food consumption to better align with our natural sleep/wake cycles that have been disrupted by modern living. I feel better following this pattern and the scientific evidence suggests that it is a straightforward, simple way to help ensure optimal health and prevent disease.