In the never-ending diet debates, people focus almost exclusively on what to eat. But when you eat may be nearly as important.
Your body’s circadian rhythms—the daily cycles that dictate when you awaken, when you’re alert, etc.—don’t just influence your behaviors like sleepiness. The time-specific, daily release of hormones determines when you get hungry and how much you eat…as well as your body’s metabolism—how efficiently you utilize fats, carbohydrates and other nutrients.
What scientists are now discovering:
Chrononutrition—the concept that food habits should align with circadian rhythms for optimal health—can have a dramatic impact on your chances of developing a variety of serious conditions. What you need to know…
Why Timing Matters
Suppose that you eat the same carbohydrate-rich meal twice a day—once in the morning and again in the evening. Both meals will trigger a rise in your blood sugar (glucose) levels, but the rise will be higher after the evening meal.
The “master clock” that controls circadian rhythms in humans and other mammals is located in a tiny brain area called the suprachiasmatic nucleus. The clock constantly sends out chemical messages that control key functions in your body. The effects can be profound.
In a study published in Proceedings of the National Academy of Sciences, nurses who changed their schedules to night shifts burned about 250 fewer calories a day, even though their jobs were the same. When researchers examined the findings of 17 studies on the effects of shift work, their analysis concluded that night-shift workers were 40% more likely than other workers to develop cardiovascular disease—possibly because their work hours were in opposition to their natural circadian rhythms.
Benefits of Early Eating
Most people get hungriest at night. But to realize the health-promoting effects of chrononutrition, the best time to eat most of your daily calories is before 2 pm. Here’s why: The body’s cells respond more readily to insulin early in the day—important for food metabolism and healthy weight maintenance, as well as preventing diabetes.
Research has shown that insulin sensitivity is higher during the hours when you’re most active. This makes sense because you need energy from your glucose reserve (which depends on insulin) when your muscles are moving. At night, when most people’s energy needs are lower, you need less glucose.
The “Three-Quarter” Challenge
What happens when you eat earlier in the day? It’s well-established that people who consume most of their calories during the daytime are less likely to be obese. That’s why I recommend consuming three-quarters of your daily calories at breakfast and lunch.
Of course, changing your eating schedule isn’t easy. People are naturally primed to eat more at night, probably because our ancient ancestors needed to store more calories to survive…and because they didn’t live long enough to suffer the effects of harmful conditions such as arthritis, dementia and diabetes.
To get started: Try to get most of your daily calories between about 8 am and 2 pm for at least three days a week—more often if you can. As you become more accustomed to eating mainly during these hours, you can transition into this schedule seven days a week.
If you get hungry at night, have a healthy snack, like raw, crunchy vegetables (or roasted veggies if you prefer).
Improve Your Blood Sugar
As mentioned earlier, insulin resistance (the reduced ability of insulin to transport glucose into cells) is higher at night than during the daylight hours. Insulin resistance is a serious health problem because it increases the risk for diabetes, obesity—and even heart disease, cancer and dementia.
Animals given high-fat meals at night are more likely to consume more calories, gain more weight and have more insulin resistance than those that are given the same meals earlier in the day.
Similar changes occur in humans. The weight-management program at Cleveland Clinic encourages not only eating 75% of daily calories before 2 pm but also increased walking and a reduction of simple carbohydrates (such as chips, white bread and other processed foods). People with diabetes who follow the program for as little as two months often improve so much that they’re able to discontinue one or two diabetes medications.
Boost Your Heart Health
A consistent finding is that daytime eating lowers high blood pressure, a leading cause of heart disease. The reduction is significant enough, in many cases, that it equals the effects of taking a blood pressure–reducing drug.
When you improve the metabolic state of the body by eating earlier (and healthier) meals, you also reduce the whole-body inflammation that can cause a gradual impairment of kidney function. Reduced kidney function can impair the renin-angiotensin system, a group of hormones that helps regulate blood pressure.
Other benefits: Daytime eating causes a decrease in triglycerides and LDL “bad” cholesterol…an increase in beneficial HDL cholesterol…and a lower risk of developing metabolic syndrome, a life-threatening constellation of symptoms that includes high blood pressure, high blood sugar and elevated triglycerides.
A Healthier Eating Plan
An optimal eating schedule can’t overcome the effects of a poor diet. Everyone should avoid most processed foods and simple sugars (such as white flour) and eat more “whole” foods, including whole grains, beans, veggies, etc. Also…
• Eat your breakfast! There are surprisingly few randomized trials on the health benefits of eating breakfast, but research has shown that people who skip this meal are more likely to have higher LDL “bad” cholesterol levels. Those with diabetes often have higher blood sugar levels later in the day when they skip breakfast.
Make breakfast either the largest or the second-largest meal of the day. People who aren’t normally breakfast eaters should at least practice “less-late” eating and get most of their calories at lunch.
• Get some protein at breakfast. A bit of protein reduces food intake later in the day. Examples: Greek yogurt (with no added sugar), salmon, steel-cut oats and nuts or seeds. Aim to get about 25 g of protein at breakfast each day.
• Skip the big suppers. Get no more than about 25% of your total daily calories from snacks/supper combined. If you do eat at the regular supper hour (around 6 pm or 7 pm), have something like a small salad, accompanied by a small portion of a protein-rich food.