Testing Out Nutrient Timing by Christina Badaracco, MPH, RD
Nutrition researchers have been studying optimal nutrient timing for many years. Their research has commonly focused on the timing around exercise and athletic activity to maximize performance and recovery. More recently, as lifestyle-related diseases have become more prevalent, people have become interested in caloric restriction and narrowing the window of eating through intermittent fasting to manage and prevent disease. And for those not looking to make such a drastic modification, recent evidence suggests that tweaking the timing of meals and redistributing macronutrient intake can promote long-term health.
Athletes and fitness professionals have long aimed to time their food intake and hydration before and after workouts and athletic events to perform at their highest ability and recover quickly. Research and recommendations first focused on carbohydrate timing, aiming to replenish glucose stores through "carbohydrate loading" before endurance exercise and after intense exercise with high-carbohydrate post-exercise meals. In recent decades, protein consumption has become a primary focus. The period after exercise has been called the "anabolic window," referring to the 30–45 minutes of muscle cells’ increased sensitivity to taking in and metabolizing nutrients for building new molecules. However, a 2020 study showed that nutrient utilization post-exercise depends on the state of nourishment before exercise, suggesting that both pre- and post-exercise periods should be considered collectively to inform dietary guidance.
Patterns of meal timing
Among the general population, the timing of eating varies widely. For example, Europeans around the Mediterranean tend to eat dinner later. Americans more commonly skip breakfast (though traditional recommendations advise against it). Within the US, people from different cultures and with varied work schedules may eat at different times—either out of necessity or out of preference. Shift work may require people to eat fewer or later meals; refer to this article for more information about the connection between circadian rhythm, food intake and health.
A pattern of eating later in the day and at night has been shown to increase biomarkers indicative of chronic disease (such as elevated insulin and fasting glucose). A 2018 study showed that later eating and consuming a higher percentage of calories in the evening were associated with increased cardiometabolic biomarkers, suggesting that eating earlier may be associated with lower disease risk. Also, a 2017 study showed that skipping breakfast is associated with increased odds of atherosclerosis, independent of cardiovascular risk factors. This also held true in a population of heart attack survivors, suggesting that adjusting meal timing may be important for secondary and primary prevention. But while we know that disrupting regular sleep-wake cycles affects weight and metabolism, it is unknown whether meal timing plays a causal role in metabolic dysregulation.
A 2015 study evaluated the use of an app to correct the increasing tendency of Americans to eat most of their calories later in the day. The authors instructed participants not to eat so late and shift their meals to a more consistent schedule (i.e., with less variation between weekdays and weekends). They used the app to monitor daily temporal eating patterns (thus minimizing error due to misreporting) and found that the app was usable and these changes led to weight loss over three weeks. Together, these studies suggest the risks of eating too many of our daily calories later in the day and the potential benefits of shifting our eating earlier.
Seemingly in contrast to this evidence, an extensive body of literature suggests many potential benefits of a pattern of intermittent fasting, which often involves restricting eating until later in the day. A key difference is its time-limited period of eating—sometimes as short as several hours over the course of the day—that leaves the body in a prolonged state of fasting, which can lead to metabolic benefits if followed very carefully and for an extended period.
Timing of macronutrients
We generally consume some of the three macronutrients—carbohydrates, fats and proteins—within each meal and snack. Depending on health conditions and dietary needs, these proportions may vary (with people on a keto diet consuming primarily fat, for example). Conventional recommendations for Americans who don’t have chronic conditions (e.g., type 2 diabetes) suggest following a "balanced plate" method, with roughly a quarter of each meal being a protein-rich food, another quarter being a whole grain and half being fruits and vegetables.
Copyright © 2011, Harvard University. For more information about The Healthy Eating Plate, please see The Nutrition Source, Department of Nutrition, Harvard T.H. Chan School of Public Health and Harvard Health Publications.
However, as with other national dietary recommendations, Americans don’t necessarily follow this method. Americans tend to overconsume protein at dinner—often including excessively large portions of meat that exceed 60% of their total daily needs. They also underconsume protein at breakfast, often consuming too much refined grain (e.g., pastries and cereal) and fewer than 15 grams of protein. However, we know it is preferable for metabolic health to balance protein throughout the day, having 20–30 grams per meal (depending on one's body size and unique medical needs). A recent cross-sectional study found that higher protein intake at breakfast or as snacks and less at dinner is associated with cardiometabolic health in adults, as measured through biomarkers such as systolic and diastolic blood pressure and insulin. Thus, Americans could benefit from reducing serving sizes of protein-rich foods in the evening and incorporating more protein-rich foods at breakfast time and in their snacks to balance intake throughout the day.
Timing of specific foods
There are, of course, also certain foods that are best avoided at certain times of the day. Most significant and familiar would be any source of caffeine—coffee and espresso contribute the most, but black, green and white tea, kombucha and yerba mate, and even chocolate contribute caffeine to the diet. Because they can potentially impair sleep, they should be avoided within at least several hours of bedtime. Further, foods that may exacerbate gastroesophageal reflux disease (GERD)—which may include spicy, acidic and high-fat foods as well as carbonated drinks—should be avoided before lying down for bed. Sugar and alcohol will also likely affect sleep quality. Finally, large meals may cause discomfort that would prevent sleep.
It is preferable to avoid eating within a few hours of bedtime, when possible. If you are hungry enough to prevent quality sleep, choose magnesium-rich foods (such as nuts, seeds, bananas and toast) before bed to promote relaxation. Other sleep-promoting nutrients include melatonin (in tart cherries, goji berries, nuts, milk, etc.), vitamin D (in fortified milk, eggs and fatty fish), zinc (in oysters, beans, whole grains, etc.) and tryptophan (in turkey, oats, bananas, cheese, etc.). Also, consuming small portions of foods, including a balance of protein and complex carbohydrates, before bed may best help to promote sleep.
Tips for timing your meals and macronutrients
When possible, aim to distribute your sources of protein throughout the day—perhaps even consuming more in the first half of the day and reducing your serving of protein in the evening.
Continue to aim for a balance of macronutrients at each eating occasion to ensure your body gets all of the macro- and micronutrients it needs.
Ensure you aren’t too hungry (or full) right before exercise and that you replenish all macronutrients (as well as water and electrolytes) between bouts of exercise.
Avoid eating too close to bedtime—particularly large servings of protein or foods that may impair sleep quality.
For people with chronic metabolic conditions and/or taking medications that depend on meal timing, consult with your dietitian or primary care physician before making any modifications.
Allison KC, Goel N. Timing of eating in adults across the weight spectrum: Metabolic factors and potential circadian mechanisms. Physiol Behav. 2018. 1;192:158-166. pubmed.ncbi.nlm.nih.gov/29486170/
Arent SM, Cintineo HP, McFadden BA, Chandler AJ, Arent MA. Nutrient Timing: A Garage Door of Opportunity? Nutrients. 2020;12(7):1948. pubmed.ncbi.nlm.nih.gov/32629950/
Gill S, Panda S. A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans That Can Be Modulated for Health Benefits. Cell Metab. 2015;22(5):789-98. pubmed.ncbi.nlm.nih.gov/26411343/
Layman DK et al. Defining meal requirements for protein to optimize metabolic roles of amino acids. American Journal of Clinical Nutrition. 2015;101(6):1330S–1338S. academic.oup.com/ajcn/article/101/6/1330S/4564493
Makarem N, Sears DD, St-Onge MP, Zuraikat FM, Gallo LC, Talavera GA, Castaneda SF, Lai Y, Mi J, Aggarwal B. Habitual Nightly Fasting Duration, Eating Timing, and Eating Frequency are Associated with Cardiometabolic Risk in Women. Nutrients. 2020;12(10):3043. pubmed.ncbi.nlm.nih.gov/33020429/
Suni E. "The Best Foods to Help You Sleep." Sleep Foundation. Updated August 14, 2020. Accessed March 31, 2021. www.sleepfoundation.org/nutrition/food-and-drink-promote-good-nights-sleep
Uzhova I et al. The Importance of Breakfast in Atherosclerosis Disease: Insights From the PESA Study. J Am Coll Cardiol. 2017;70(15):1833-1842. pubmed.ncbi.nlm.nih.gov/28982495/
Vieira Musse GN et al. Skipping breakfast concomitant with late-night dinner eating is associated with worse outcomes following ST-segment elevation myocardial infarction. European Journal of Preventive Cardiology. 2020;27(19):2311-2313. journals.sagepub.com/doi/10.1177/2047487319839546
Christina Badaracco, MPH, RD
Christina is a registered dietitian and author who aims to improve access to healthy and sustainable food and educate Americans about the connections between food and health. She loves to experiment with healthy recipes in the kitchen and share her creations to inspire others to cook.
Christina completed her dietetic internship at Massachusetts General Hospital and earned her Master of Public Health degree from the University of California, Berkeley. Previously, she graduated with a degree in Ecology and Evolutionary Biology from Princeton University, after conducting her thesis on sustainable agriculture and energy in Kenya. She has done clinical nutrition research at the National Institutes of Health, menu planning and nutrition education at the Oakland Unified School District and communications at the Environmental Protection Agency's Office of Water. She has also enjoyed contributing to children’s gardens, farmers markets and a number of organic farms.