Sleepy After Eating: Is Blood Glucose the Cause?

When you sit down after lunch, your eyelids get heavy. This drowsiness, commonly called a “food coma,” is often blamed on “rising blood glucose.” Is that really so?

Post-meal sleepiness has several causes

Post-meal sleepiness can’t be explained by a single reason. Because of the body’s daily rhythm, alertness dips once in the early afternoon, and lunchtime happens to fall right around then. Many people feel sleepier after too little sleep the night before, after eating more than usual, or after a meal heavy in carbohydrates such as rice, noodles and bread.

How is it related to blood glucose?

Everyone’s blood glucose rises after eating. What matters is how high it rises and how fast it comes back down. In a study by Stanford University in the U.S. that observed people’s blood glucose throughout the day with continuous glucose monitors, even people classified as normal by standard tests spent about 15% of the day with blood glucose in the prediabetes range. Even when people ate the same food, the shape of the blood glucose rise varied widely from person to person.

So we cannot conclude that post-meal sleepiness is a blood glucose problem, but it is worth remembering that even when fasting blood glucose is normal, post-meal blood glucose can move on its own.

Get tested if these signs appear together

• If you have intense thirst and urinate often along with post-meal sleepiness
• If you are losing weight for no reason
• If a family member has diabetes and your waist circumference is at or above the criterion (Korean criteria: 90 cm for men, 85 cm for women)

Habits that make the time after a meal lighter

• Don’t eat a lot at once. Overeating increases both sleepiness and the rise in blood glucose after a meal.
• Cut back on refined carbohydrates and eat more vegetables and mixed grains. Dietary fiber slows sugar absorption. A typical ingredient for supplementing the fiber missing from meals is resistant maltodextrin.
• Get enough sleep. Lack of sleep is bad not only for daytime sleepiness but also for blood glucose control.
• Don’t sit for long periods. At least 150 minutes of physical activity per week is the foundation of blood glucose control.