Making Breakfast the Biggest Meal May Help Control Glucose All Day

High-energy breakfast with low-energy dinner decreases overall daily hyperglycaemia in type 2 diabetic patients: a randomised clinical trial, by Jakubowicz and colleagues. Diabetologia 2015 March 1 [Epublished ahead of print]

What is the problem and what is known about it so far?

People with diabetes routinely get a lab test called the A1C to find out how well they are controlling their blood glucose (sugar) levels. The A1C test measures overall glucose control during the past 2 to 3 months. However, people can have an A1C in the target range and still have harmful glucose spikes after meals. High blood glucose after meals accounts for 30 to 70 percent of a person’s total A1C and raises the risk for heart and blood vessel diseases and other complications. Diabetes health care professionals need to design care plans that specifically target glucose spikes after meals.

Research has shown that glucose levels rise in response to food differently at certain times of the day. A meal eaten in the evening will raise blood glucose higher and keep it high for longer than if the same meal were eaten in the morning. This happens in part because the hormones and enzymes that help to process food and control blood glucose are released at different rates during periods of darkness and light each day. However, the timing and content of meals can also affect how the body processes food. Studies have shown that changing the usual meal schedule (such as skipping breakfast) or having certain meal patterns (such as eating high-energy meals at dinner) can throw off the way the body handles food, leading to high glucose levels after meals and higher A1C levels. In contrast, in animal studies, diets featuring high-energy morning feedings with no evening feedings or time-limited feeding periods reduced both glucose levels and weight. These studies suggest that it’s not just when you eat, but also what and how much you eat at different times of the day that affect glucose levels. However, this has not been widely explored in people with type 2 diabetes.

Why did the researchers do this particular study?

The researchers wanted to find out whether two different diets that provided the same amount of energy but at different times of the day would affect glucose levels differently.

Who was studied?

The study included 18 adults with type 2 diabetes.

How was the study done?

Half of the participants ate a diet that featured high-energy breakfasts (704 calories) and lower-energy dinners (205 calories), while the other half did the opposite, eating high-energy dinners (704 calories) and lower-energy breakfasts (205 calories). Both groups ate the same lunch (603 calories). The participants followed their assigned diet for 1 week. Their glucose levels and the levels of hormones and enzymes that affect food processing (insulin, C-peptide, and glucagon-like peptide-1 [GLP-1]) were measured and compared.

What did the researchers find?

The participants who ate high-energy breakfasts and lower-energy dinners had lower glucose levels and higher levels of insulin, C-peptide, and GLP-1 than those who ate high-energy dinners and lower-energy breakfasts. These levels were maintained both after the meals and throughout the day. Although both groups ate the same lunch, the group that had high-energy breakfasts had lower glucose and higher insulin after lunch than the group that ate high-energy dinners. Overall, glucose levels rose less and stayed high for a shorter time period after the meals for people who ate the high-energy breakfasts than for those who ate the high-energy dinners.

What were the limitations of the study?

Because the meals had different levels of protein, fat, and carbohydrate at different times of the day, some of the results may have been because of the timing of eating various types of food rather than the total amount of energy eaten at the meals. Also, because the study did not include a group of healthy participants, the researchers could not tell whether the diets would have the same effects in people without diabetes. Finally, the researchers did not measure and compare insulin sensitivity, the amount of glucose produced in the body, or how fast the stomach emptied after meals, all of which may have affected the results.

What are the implications of the study?

Eating the largest meal of the day at breakfast and the smallest at dinner may help people with type 2 diabetes to better control their blood glucose. Although this study focused on short-term effects, routinely following such a diet could lower A1C and reduce the risk of heart and blood vessel diseases and other complications.

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