Bacon and eggs or meatloaf and potatoes? The timing of high-calorie meals affects glucose levels in type 2 diabetes

This study examined whether the timing of high calorie intake (breakfast versus dinner) affects glucose (sugar) and insulin (the hormone that breaks down the glucose from food) levels in type 2 diabetes patients.

The body has an internal clock, known as the circadian clock. This internal clock is why we get tired at night and feel awake in the morning. The circadian clock affects many other body processes as well, including levels of insulin and glucagon-like peptide 1 (GLP-1; a hormone that increases insulin release). The timing of meals can have an effect on the circadian clock. For instance, regularly skipping breakfast or having a large dinner can disrupt the normal release of hormones. This can lead to increased and variable blood glucose levels in patients with type 2 diabetes. It is not known whether the timing of large meals, either at breakfast or dinner, has an effect on blood glucose and insulin levels over the course of a day.

This study examined whether the timing of a high-calorie meal influenced glucose control in 18 patients with type 2 diabetes. Each patient followed two different types of diet for 7 days each. One diet consisted of a high-calorie breakfast, followed by a medium-sized lunch, and a small dinner. The other diet consisted of a low-calorie breakfast, a medium-sized lunch, and a high-calorie dinner. The patients followed each diet at home for 6 days, then had a day of testing. During testing, blood glucose, insulin, and GLP-1 levels were measured before and at regular time points for 180 minutes after each meal.

Over the entire day of testing, glucose levels were 20% lower, while insulin and GLP-1 levels were 20% higher after the high-calorie breakfast diet compared to the high-calorie dinner diet. In the 180 minutes following a high-calorie breakfast, glucose levels were 24% lower, insulin was 11% higher, and GLP-1 was 30% higher than after a high-calorie dinner.

In the 30 minutes following a high-calorie breakfast, glucose levels were 10% lower than they were in the 30 minutes following a high-calorie dinner, and they decreased more rapidly. Insulin levels increased faster following the high-calorie breakfast, and peaked at 60 minutes after. The peak insulin level was at 120 minutes following the high-calorie dinner. GLP-1 levels peaked at 30 minutes following a high-calorie breakfast, and at 60 minutes following a high-calorie dinner.

After lunch, glucose levels were 21–25% lower after the high-calorie breakfast diet. 30 minutes following lunch, insulin levels were 50% higher in the high-calorie breakfast group.

This study concluded that a meal plan including a high-calorie breakfast and a lower-calorie dinner can improve blood glucose and increase insulin and GLP-1 levels over the course of a day compared to a diet based on high-calorie dinners.

Please consult with your doctor if you are unsure of how to best manage your diet to control your diabetes.