The age-old debate of what we should be eating has been around forever; vegan vs. high carb, low fat vs. Paleolithic, etc. An equally important question to consider though, is WHEN should we be eating? Can the timing of our meals help our bodies use the nutrients its consuming to help drive our health goals? Can the time of day we eat have a great impact on our health? What about the frequency of meals and snacks? New research is indicating yes, it has an important impact!
1. Eat When Your Body is More Insulin Responsive: Insulin sensitivity is a common term when thinking about diabetes, but insulin impacts just about everyone. Insulin is a hormone in our bodies that is produced and released when certain nutrients are present in our blood, specifically carbohydrates and protein. When we consume food rich in carbohydrates and/or protein, such as a hamburger, the pancreas responds by producing and releasing insulin into our blood stream. The insulin then helps shuttle these nutrients into our cells. When someone is insulin sensitive, insulin has a much easier time getting these nutrients into the cells.
On the contrary, when someone is insulin resistant, the cell is less responsive to the surge of insulin and does not easily allow the glucose and amino acids (from protein) inside the cells. In response, blood glucose levels usually increase, and more insulin is produced. If this insulin resistant state happens too often and blood glucose and blood insulin remain elevated, it can lead to various chronic diseases such as type 2 diabetes.
Ideally, we want to be in a state of insulin sensitivity, which is easier on the body and reduces the risk of developing chronic disease & illness.
2. After Exercise: Aside from what we fuel our body with, insulin sensitivity can also be influenced by exercise. Exercise has an impact on how our bodies utilize and store glucose. Glucose is the preferred fuel for the body, as it requires less time and fewer metabolic processes to use. Glucose is a quicker energy source than fats and protein, which makes glucose our body’s go-to fuel when exercising.
Glucose is stored in our liver and muscles as glycogen. When exercising, our bodies use more glucose for the increased fuel demand, but also to maintain regular blood glucose levels for normal bodily functions. The increase with which stored glycogen gets depleted is related to the intensity of the exercise performed. The higher intensity of the workout, the more glucose fuel our body will burn. Interval training and heavy weight training are two common types of exercises that deplete glycogen at a more rapid pace. When you consume a meal after glycogen-depleting exercise, your body is able to store more glycogen. So, when eating carbohydrates that normally elevate blood glucose, more of that glucose will be transported to the liver and muscles to replenish the glycogen, instead of remaining in the bloodstream. When in a glycogen-depleted state post workout, the same high-carb meal will produce a lessened glycemic response (i.e., rise in glucose and insulin) compared to that same carbohydrate intake when in a glycogen-replenished state before exercising. If you’re considering the best time for your weekly cheat meal or deciding when to consume your high-carb food item, it’s likely best to do so after you work out.
If you’re interested in increasing your body composition, studies have shown that exercising in a fasted state can increase your lipid (fat) oxidation. This can potentially contribute to more fat loss. Furthermore, having a post-exercise meal containing protein has been shown to increase myofibrillar protein synthesis, which contributes to overall muscle growth. Timing your meals around your exercise regime and mapping out what you will eat around your workout schedule can have some positive health benefits. However, keep in mind that the response you have to that meal can also depend on the length of exercise, time of day and whether or not you have already eaten that day. Additionally, how your body responds to and utilizes nutrients, body composition, underlying health conditions, medications, and sleep schedule also factor in.
3. Time Of The Day: Time restricted feeding (TRF) is a common fasting protocol used by many people for various reasons such as improved glycemic response, weight loss, and better energy. During TRF, food is consumed within a predetermined time frame, and the remaining hours of the day are spent fasting. A common protocol for TRF is to skip breakfast and not eat the first meal of the day until lunch/around noon and stop eating after dinner around 8pm, giving you a 16:8 TRF window (i.e., 16 hours of fasting and 8 hours of eating). However, recent research has come out arguing for a shift towards early TRF, or ETRF. This would mean having your first meal of the day around 8am and stopping eating around 2-4pm, depending on your feeding window. You would then skip dinner and not eat until 8am the next day.
One study took non-diabetic patients and randomized them into either the ETRF group (eating their meals from 8am-2pm) or the control group (eating their meals from 8am — 8pm). Both groups ate the same meals per day and only the feeding window was different. Results showed that the ETRF group had lower 24-hour glucose levels, lower glucose levels at night, lower insulin levels, and less glucose excretions (sharp elevations in glucose above normal). When the researchers looked at markers for circadian rhythm, they found that specific circadian clock genes such as SIRT1 and the autophagy gene LC3A were increased, and a more favorable cortisol pattern was seen in the ETRF group.
A second similar study looked at ETRF in pre-diabetic men. The experimental group restricted their food to a 6-hour feeding window and were required to have their first meal between 6:30–8:30am and their last meal no later than 3pm. The control group ate for a 12-hour period and consumed the same meals provided to the ETRF group. Results from the study showed that ETRF increased insulin sensitivity, improved beta cell function, lowered blood pressure and oxidative stress, and decreased the desire to eat in the evening, which may assist with weight loss and improve health overall.
4. Meal Frequency: Meal frequency has also been a common topic of debate. Arguments for 3 meals per day, 3 meals and 2 snacks, 6 small frequent meals, one meal per day and intermittent fasting are common in the nutrition world. Even though different meal plans can work for different people, in general, we probably don’t need as much as we think.
Proponents for 5–6 small meals per day argue that continuous food keeps the metabolism running at a higher rate and helps maintain better satiety throughout the day. For some people this may be true, but some studies have been done to challenge this argument. One study showed no significant difference in weight loss while eating 3 meals plus 3 snacks per day compared to 3 meals per day. Another study showed that eating 6 small meals per day resulted in less feelings of being full. In addition, 5–6 meals allow for more deviation from a healthy meal plan. Eating more frequently uses a lot more willpower and provides increased temptation to eat processed snacks, desserts, and sugary beverages. In conclusion, aim for 3 meals per day, or even less if you practice intermittent fasting or time-restricted feeding. Sometimes 1 or 2 meals will be enough.
5. Are you hungry?: From an early age many of us were taught to “not leave the dinner table until our plate is clean.” Of course, our parents had the best intentions, but they didn’t have the knowledge we do today. However, the ideology that finishing everything that is in front of us has created the false understanding that we will be doing our body a disservice by not keeping our system fully fueled 24/7.
Quite to the contrary, our bodies are well oiled machines that have built-in mechanisms to deliver our cells with the necessary fuel and energy they need even during periods of fasting. We keep stores of energy in our bodies in the form of glucose, or sugar (glycogen in our liver and muscles) and fat (adipose tissue under our skin and around our organs). When in the absence of nutrients for a prolonged amount of time, our body can tap into these reserves and convert them into fuel used for energy. Just think of our hunter and gatherer ancestors who sometimes went days without eating, but still had enough energy to hunt and capture their prey. They utilized their own energy stored to fuel them in the pursuit of food.
Along with what you eat, knowing when to eat can provide a significant contribution to your overall health. To help reduce your risk of chronic disease, improve body composition, and optimize circadian rhythm, consider eating meals earlier in the day as opposed to later. Time your meals, specifically, those containing higher carbs and protein, to after your work out. To assist with hunger levels and prevent over consumption, think about reducing the number of meals you have per day. Lastly, and most importantly, if you’re not hungry, don’t eat!