For the millions of people in the UK managing Type 2 diabetes, shifting exercise sessions to the afternoon could be a simple yet powerful strategy for significantly better blood sugar control, according to a new scientific review.
The analysis, published in the journal Trends in Endocrinology and Metabolism, examined multiple studies comparing workout timings and concluded that afternoon or evening physical activity produces more substantial and enduring improvements in glucose regulation for diabetics. Identical exercise performed in the morning, however, was frequently found to lead to elevated blood sugar and diminished insulin responses.
The crucial role of the ‘dawn phenomenon’
The explanation for this stark difference lies in a natural bodily process known as the “dawn phenomenon,” according to Professor Harriet Wallberg-Henriksson, a professor of physiology at the Karolinska Institute in Stockholm and senior author of the review. Upon waking, the body experiences a surge in hormones, including cortisol, growth hormone, glucagon and epinephrine. This surge helps rouse the body from sleep but also triggers the liver to release stored glucose into the bloodstream.
In individuals with a healthy metabolism, the pancreas responds promptly by producing insulin, which efficiently channels that sugar into muscles for energy. For those with Type 2 diabetes, however, the body either produces insufficient insulin or resists its effects—a state known as insulin resistance. This means the glucose released during the dawn phenomenon is not properly absorbed, causing blood sugar levels to climb and remain elevated each morning.
Vigorous exercise early in the day can amplify this problem. Exercise itself stimulates a further release of cortisol, which in turn prompts the liver to release even more glucose. For diabetic muscles already struggling with insulin resistance, this additional glucose flood is difficult to manage, leading to a counterproductive spike in blood sugar levels. This circadian misalignment, where the body’s internal clock and metabolic processes are out of sync, is a key area of study for researchers like Professor Juleen Zierath, a physiologist at the Karolinska Institute and co-author of the review, whose work explores how timing impacts metabolism in Type 2 diabetes.
Study evidence points to afternoon advantage
The review’s conclusions are supported by consistent data across multiple investigations. “Most studies report higher postexercise glucose levels in individuals with type 2 diabetes in the morning compared with the afternoon,” the authors noted. One cited study tracked middle-aged men with Type 2 diabetes on identical intensive exercise programmes at different times. Those who trained in the afternoon achieved lower, healthier glucose readings that lasted up to 24 hours, while the morning group saw raised blood sugar and compromised insulin sensitivity for a similar duration.
Significant supporting evidence comes from analyses of the large Look AHEAD (Action for Health in Diabetes) trial. Research stemming from this study, published in journals such as Diabetes Care, has consistently shown that participants who were most active in the afternoon experienced the greatest reductions in blood glucose levels. Further studies in Diabetologia found afternoon or evening activity was associated with up to 25% reduced insulin resistance compared to evenly distributed activity, while work in the American Journal of Medicine indicated physical activity may be most effective later in the day, especially after meals.
Exercising 30 to 45 minutes after eating has also shown promise as a specific timing strategy, helping to blunt post-meal blood sugar spikes—a major concern in diabetes management.
Recommendations: consistency and caution first
Despite the clear advantages of afternoon workouts for glucose control, the researchers unanimously stress that any exercise is vastly superior to none. “The most important message remains that exercise at any time is better than no exercise at all,” said Professor Juleen Zierath.
For those who favour or can only manage morning sessions, experts advise modifying the intensity. Professor Wallberg-Henriksson recommends keeping early workouts modest, as gentler activities like brisk walking do not appear to produce the same problematic time-dependent effects as strenuous exertion. This view is echoed by exercise scientist Trine Moholdt of the Norwegian University of Science and Technology, who notes that for most people, the optimal time is simply whenever they can consistently fit it into their routine.
Safety precautions remain essential. Exercise is generally safe and beneficial for blood pressure, strength and glucose control in Type 2 diabetes, but individuals on insulin or certain medications must monitor blood sugar closely to prevent hypoglycemia. Experts also advise those with diabetes to check for ketones in their urine before exercising if their blood sugar is already high, as exercising with elevated ketones can risk a dangerous condition called ketoacidosis. As with all aspects of diabetes care, exercise timing is one component of a comprehensive approach that includes diet and medical treatment.