If you are like most people, you eat any time you are hungry, bored, or need a mood lift.
A recent study that used a smart phone app to track activity and food intake found that the average subject ate almost continuously over the course of 15 hours, leaving only 9 hours for fasting when they were asleep. The number of eating events ranged from 4.22 to 15 over the course of the day, with a significant portion of people eating every 90 minutes.
This chronic overexposure to food is one of the factors that is driving the obesity epidemic. And it’s not just that people are eating more calories as they graze their way through their days. Eating frequently or at the wrong times alters the body’s biorhythm and harms the metabolism, leading to an increased risk of diabetes, heart disease, and depression.
On the flipside, chrono-nutrition, or the intelligent planning of meals, can improve the body’s natural biological rhythm for better body composition, health, and physical performance. Chrono-nutrition is even being used to slow the aging process. This article will give you an overview of how nutrition impacts circadian function and provide strategies for timing your nutrients for better health and performance.
What Is A Circadian Rhythm?
The circadian system is a network of clocks in the human body that control release of chemical messengers, such as hormones and neurotransmitters, that dictate when we are hungry, sleepy, wakeful, energetic, relaxed, etc.
The master clock is known as the suprachiasmatic nucleus (SCN) and it is located in the hypothalamus of the brain. There are also peripheral clocks located in different organs and cellular clocks located in individual cells. The SCN helps keep the peripheral and cellular clocks in time. However, the peripheral and cellular clocks can develop their own timing based on our behavior and habits.
Why so many different clocks?
By having their own clocks, cells can ensure that incompatible processes like anabolism (building of tissue) and catabolism (breaking down of tissue) don’t happen at the same time.
What Regulates Our Circadian Rhythm?
Although a variety of behaviors impact circadian function, the two primary factors are light/dark exposure and food. Exposure to light is a major time cue that helps entrain the central SCN clock to our 24-hour day.
For example, bright light exposure in the morning shuts off release of the sleep hormone melatonin and increases release of testosterone in the morning, having an energizing effect. Cortisol spikes to help us get out of bed, and then it curves downward over the course of the day, having sharp dips in response to meals when insulin is elevated. Cortisol reaches a low point at night, when darkness stimulates melatonin, downregulating brain function and getting us ready for sleep.
Food primarily impacts our peripheral clocks, such as those in the liver, gut, and pancreas. For example, when you eat at the same time every day, the GI tract responds by releasing enzymes involved in digestion in preparation for breaking down food. The stomach begins contracting (making the rumbling noise that we associate with hunger) in preparation for incoming nutrients. Hunger hormones peak prior to your regularly scheduled meal time and then decline, helping to moderate appetite during fasting periods.
How Do Circadian Clocks Get Out Of Synch?
One theory is that our modern habits are disrupting our natural circadian clocks: In pre-industrial times we would rise with the dawn and go to bed close after sunset. We would forage, hunt, and eat during daylight, with the night reserved for resting and fasting. Our internal clocks were tightly synchronized to the solar day.
Electric lights, round the clock food access, shifting schedules, and screen exposure all impact our biorhythms and alter the appropriate phase timing of our body's clocks. Let’s take eating: Chronic eating (eating more or less continuously during the day) or overeating (eating too many calories at meals) stimulates the pancreas to release a steady stream of insulin in an effort to regulate blood sugar. Over time, the beta cells of the pancreas can become damaged, leading to diabetes.
The liver also takes a hit in response to chronic eating. An organ involved in carbohydrate and fat metabolism, the liver functions on roughly a 4-hour circadian function. When it is continuously active, you increase risk that fat will be deposited in the liver, leading to fatty liver—a disease that was virtually unheard of except for in alcoholics until recently.
The gut is another organ that requires careful circadian function. An important action for the gut is motility, which occurs once digestion is finished. The muscles of GI tract stretch and contract, enabling food to progress through the intestines while, at the same time, ensuring absorption of nutrients. Chronic eating inhibits this activity and impacts the circadian rhythm of bacteria in the gut. You probably know that gut bacteria play a role in digestion and calorie absorption. Some research indicates that when gut bacteria get out of synch, calorie absorption increases, contributing to fat gain and obesity.
Hormones that regulate hunger and appetite are also impacted. When you skip meals or eat at random times, ghrelin and neuropeptide Y, which are signals that “turn eating on” are released, making it more likely you will overshoot your calorie needs and gain body fat.
Animal studies support these theories: When animals eat at times when they would typically be asleep, they tend to get fatter, develop insulin resistance, and experience metabolic disorders. By having them eat during typical feeding times and limiting the duration of the feeding windows to 12 hours or less, they are leaner and healthier, even when fed unhealthy high-fat, high-sugar diets.
Chrono-Nutrition Tips For Leanness, Health & Performance
The first step to chrono-nutrition is to realize that everyone is unique. There are large individual differences in the timing of circadian rhythms, which are most influenced by your unique chronotype.
Chronotype refers to whether you are more of a “lark”, or morning person, or an “owl”—an evening person. Most people experience shifts in their tendency across their lifetime, such that they are larks as younger children, owls as teenagers, and larks again as they enter their golden years. Beyond this pattern, people of any age can be larks or owls, however, as we’ve discussed in this article, it's also possible to completely alter the system via our daily habits, such that we experience peak alertness at the wrong times or become chronically tired.
What follows are tips for making the most of chrono-nutrition.
#1: Sleep According To Your Chronotype
Although not always possible, setting up your sleep-wake schedule to synch with your natural tendency will improve circadian function and set the stage for success with strategically timed nutrients and meals.
#2: Optimize Your Light/Dark Exposure
Getting bright sunlight in the morning will anchor your body’s clock, but unnatural lights from cell phones and other screens have a harmful effect. Studies show that blue light exposure from screens stimulates food intake and increases how many calories people eat during the day. At night, the effect is amplified since light from screens is known to disrupt circadian function and release of the hormone melatonin.
#3: Eat At Consistent Times
Food is a primary regulator of your body’s clock. Eating at consistent times can improve circadian function and help ease other activities, including sleep, waking up in the morning, digestion, and stress management.
#4: Use A 10- To 12-Hour Eating Window
Instead of eating throughout your entire waking day, limit your food intake to a 10- to 12-hour window to give your digestion a chance to rest. A restricted eating window can help you avoid overshooting calorie needs and improve your body’s ability to burn fat and process carbohydrates.
#5: Eat During Daylight
Eating the majority of calories earlier in the day, or eating lunch earlier have both been associated with greater weight loss in observational studies. The amount of calories your body burns digesting food (known as diet induced thermogenesis) is higher earlier in the day and may explain these findings.
#6: Don’t Eat When You Would Normally Be Asleep
If you are awake when your natural inclination would be to sleep, such as after waking to an alarm in the morning before work, you may want to wait until you would normally be awake before eating.
#7: Leave At Least Four Hours Between Meals
Choosing a lower meal frequency (2 to 4 meals a day) and eating about every 4 hours can allow you to prevent excessive hunger, while avoiding the negative metabolic effects of chronic eating.
#8: Eat Around Workouts
Eating after exercise improves absorption of nutrients and encourages calories to be portioned favorably: Carbs are used to synthesize glycogen and protein stimulates protein synthesis for repair and recovery.
#9: Maintain Your Schedule On The Weekend
On the weekends, people eat more meals, eat more calories in those meals, and have a longer eating window, while also sleeping and going to bed later. Known as social jet lag, most people experience a discrepancy in when they do basic activities on the weekend compared to during the week, which is theorized to increase our risk of disease and obesity.
#10: Load Up On Antioxidant-Rich Foods
Phytonutrient-rich foods, such as brightly colored fruits and vegetables, possess biological activities that influence circadian rhythms and counter inflammation, which harm cells and DNA. Cherries, bananas, watermelon, tomatoes, grapes, berries, leafy greens, and almonds are all antioxidant-rich foods that can improve circadian function.