Have you ever felt that afternoon slump after a big lunch or found yourself wide awake after a late-night snack? These experiences aren’t random. Your body operates on an internal clock, much like a built-in schedule, called the circadian rhythm, and it affects everything, including your sleep patterns, hormones and digestion.
A recent study demonstrates another area that the circadian rhythm controls, particularly your blood sugar levels. It provides an interesting insight — it’s not just what you eat that matters; when you eat your meals do too, meaning that timing your meals based on your circadian rhythm significantly impacts your glucose levels and, ultimately, your overall health.1
‘Late Eaters’ Have Higher Glucose Levels and Are More Prone to Weight Gain
A study published in the journal Nutrition & Diabetes found that people who tend to eat later in the day have a higher risk of problems with blood sugar control. This means their bodies have a harder time regulating glucose, the main sugar found in the bloodstream.2
The researchers studied 26 people between the ages of 50 and 70 who were either overweight or obese and had either prediabetes or Type 2 diabetes. They divided the participants into two groups based on when they ate their meals — “early eaters” who ate most of their calories before evening and “late eaters” who ate almost half (45% or more) of their calories after 5 p.m.
To make sure the comparison was fair, both groups ate the same types and amounts of food. The only difference was their eating schedule. Participants used a mobile app to record all their meals.
The study’s key finding was that people who ate more later in the day had more trouble managing their glucose tolerance — their body’s ability to absorb glucose and use it for the brain and tissues — no matter their weight or what kinds of foods they ate. These “late eaters” also tended to eat more carbohydrates and fats in the evening. According to the researchers:
“Adding to previous findings on the detrimental effect of late eating on BMI [body mass index] and metabolism and its association with poorer diet, we now observed that the association of LE [late eaters] with poorer glucose tolerance is independent of greater body weight, fat mass, calorie amount, or poorer diet composition.”3
Dr. Diana Díaz Rizzolo, a member of the Faculty of Health Sciences, UOC and the study’s lead author, explained:
“The body’s ability to metabolize glucose is limited at night, because the secretion of insulin is reduced, and our cells’ sensitivity to this hormone declines due to the circadian rhythm, which is determined by a central clock in our brain that is coordinated with the hours of daylight and night.”4
Our Inner Timekeeper — The Circadian Rhythm and Your Metabolism
Think of your body as a finely tuned orchestra. Each organ and system have a role to play, and the circadian rhythm is the sync over a 24-hour period. Just like a conductor uses a baton, our bodies use light conductor, keeping everything in and darkness to stay on schedule.
Sunlight signals our bodies to release hormones like cortisol, which helps us feel alert and gives us energy. When darkness falls, our bodies produce more melatonin, a hormone that promotes relaxation and prepares us for sleep.5
This internal clock also affects how our bodies process food. Our metabolism, the process of turning food into energy, follows this daily rhythm. For example, our bodies are usually better at using insulin — a hormone that helps move sugar (glucose) from our blood into our cells for energy — in the morning.6 Insulin acts like a key that unlocks the door to your cells, allowing sugar to enter and provide energy. This is why our bodies handle sugars more efficiently earlier in the day.
This brings us to an important area of research called chrononutrition, which looks at how our eating patterns line up with our internal clock.7 As the featured study illustrates, consistently eating at times that don’t match our natural rhythms, like frequently eating late at night, throws off our metabolism.8
This is especially relevant for shift workers who often have irregular sleep and eating schedules and are more likely to experience metabolic problems.9 When your circadian rhythm is disrupted, it leads to insulin resistance. This makes it harder for sugar to get into your cells, leading to high blood sugar levels and increasing the risk of Type 2 diabetes.10
When You Eat Matters — Meal Timing and Blood Sugar Control
Now that we understand how our internal clock affects metabolism, let’s look at how the timing of our meals specifically impacts blood sugar control. Here’s how breakfast, late-night eating, how often you eat and even intermittent fasting affect your blood sugar:
• Skipping breakfast — Skipping breakfast could set you up for blood sugar problems throughout the day. Research shows that people who skip breakfast often have bigger blood sugar spikes after lunch and dinner.11 It’s as if skipping breakfast makes your body less efficient at handling sugar later on, creating a ripple effect throughout the day.
• Night owl nibbling — Late-night snacking is a common culprit when it comes to blood sugar issues. Your body is like a factory that powers down at night. Just like a factory slows its operations, your body’s ability to process sugar also slows down in the evening.
Eating late at night is like asking the factory to suddenly ramp up production when it’s already winding down. This leads to weight gain and increases the risk of Type 2 diabetes. Considering that our ancestors likely ate most of their food during daylight hours when they were active, aligning our eating habits more closely with this natural pattern is beneficial.
• Spreading the carb load — The frequency of your meals also plays an essential role in blood sugar management. Instead of eating three large meals, try spreading your carbohydrate intake throughout the day with smaller, balanced meals and snacks.
This helps avoid high blood sugar spikes that happen after eating a lot of carbs at once. It’s like giving your body small, manageable doses of fuel instead of one big overload, allowing it to process the sugar more steadily.
• Intermittent fasting — Another approach to consider is intermittent fasting (IF), which involves cycling between periods of eating and fasting. Some studies suggest IF improves how well your body uses insulin and helps lower blood sugar levels.
There are different ways to do IF, such as the 16/8 method (eating within an 8-hour window and fasting for 16 hours) or the 5:2 diet (eating normally for five days and restricting calories for two).
Implement Healthier Habits with These Strategies
Now that you understand how meal timing affects your blood sugar, below are some easy-to-follow tips to improve your eating habits:
• Make breakfast a priority — Think of breakfast as the first log you put on the fire of your metabolism each day. It gets things going and sets the tone for your blood sugar control. When you skip breakfast, it’s like trying to start a fire with damp wood — it just doesn’t work as well.
Instead of sugary cereals or pastries, which cause a quick spike and then a crash in your blood sugar, try these simple swaps:
◦Yogurt with ripe fruit — Yogurt made from raw, grass fed milk is packed with protein to keep you feeling full and satisfied. Adding fruit gives you vitamins, fiber and natural sweetness. A sprinkle of cinnamon might even help with blood sugar control.
◦Whole-wheat toast with an organic pasture-raised egg — This simple meal provides a good mix of healthy fats, protein and complex carbohydrates.
• Avoid late-night snacks — Remember the campfire analogy? Eating late at night is like throwing logs on a dying fire. Your body isn’t as efficient at processing food late in the day, so you’re more likely to have excess sugar in your bloodstream. To avoid late-night eating:
◦Set a regular dinner time — This helps regulate your hunger cues. Aim to eat dinner a few hours before bedtime to give your body time to digest.
◦Eat without distractions — When you eat while watching TV or using your phone, it’s easy to overeat. Try to create a calm environment for meals.
◦Establish a relaxing bedtime routine — Sometimes, late-night cravings are due to boredom or habit. A relaxing routine, like reading or taking a warm bath, helps you avoid the urge to snack. If you still feel hungry, try a glass of water or herbal tea. For more useful strategies to help you get high-quality sleep, read “Top 33 Tips to Optimize Your Sleep Routine.”
• Distribute your carbs wisely — Carbohydrates are your body’s main source of energy, but some carbs are digested faster than others. Think of it like different types of fuel — some burn quickly, causing a sudden burst of energy followed by a crash, while others burn slowly and provide steady energy. To distribute your carbs wisely:
◦Choose whole grains — Whole grains have more fiber, which helps regulate blood sugar.
◦Eat plenty of ripe fruits and well-cooked vegetables — These are packed with vitamins, minerals and fiber, which helps slow down the absorption of their natural sugars.
◦Watch your portions — Even healthy carbs raise blood sugar if you eat too much at once. Balance your meals with protein and healthy fats. Include at least 0.8 grams of protein per pound of lean body mass, and ensure one-third of your protein intake is collagen-based.
As for healthy fats, choose grass fed beef tallow, ghee and coconut oil for cooking and eliminate vegetable oils that are loaded with linoleic acid (LA). Avoid processed foods and restaurant meals, which are often loaded with these oils.
• Small changes make a big impact — Making big changes to your diet is tough, so start small and make gradual, sustainable changes. Remember, consistency is key. Here are some easy ideas to get you started:
◦Focus on one meal — Start by improving one meal, like breakfast, and then gradually work on other meals.
◦Set realistic goals — Set small, achievable goals, like eating breakfast every day for a week or swapping sugary drinks for water.
◦Track your progress — A food journal or app will help you stay motivated and see how far you’ve come. My Mercola Health Coach App has a Food Buddy feature to help guide your food choices and keep track of your health goals. It’s coming out very soon, so stay tuned.
