Diabetes mellitus affects more than 530 million people worldwide, according to the International Diabetes Federation, and is one of the leading causes of premature death globally. Physical activity has been recognized for decades as a fundamental pillar of non-pharmacological treatment for diabetes, capable of improving insulin sensitivity, reducing blood glucose levels, and preventing cardiovascular complications. However, a new generation of research has begun to explore a variable that until recently remained in the background: the time of day when exercise is performed. This approach—known as chrono-exercise—opens a new therapeutic door that could transform medical recommendations for millions of diabetic patients. For years, the medical recommendation was simple: move more. Walking, swimming, cycling—any physical activity was better than none for a person with diabetes. But science is advancing, and today that advice has an important nuance: when you exercise can be just as relevant as how much you do. New research confirms a 2024 study led by researchers from the University of Granada (Spain), published in the journal Obesity, which analyzed how the time of day when moderate-to-vigorous physical activity is concentrated affects glucose levels in overweight or obese adults. The results were conclusive: accumulating more exercise between 6 pm and midnight was associated with a notable improvement in blood sugar regulation, compared to those who were more active in the morning. The Muscle That Works at Night The physiological explanation behind this phenomenon has to do with how the body processes glucose throughout the day. During exercise, muscles take up glucose from the bloodstream through an insulin-independent mechanism: Muscle contractions activate special transporters that allow sugar to enter cells directly to be used as energy. This effect persists for two to 48 hours after physical activity ends. When exercised in the late afternoon or evening, this muscle uptake effect coincides with the times when blood glucose levels are typically highest—especially after dinner, the last meal of the day—thus enhancing its impact on overall glycemic control. The Mayo Clinic notes that nighttime exercise can improve sleep,which is essential for metabolic management, provided the exercise is not excessively intense right before bedtime. Implications for Clinical Practice: These findings have direct implications for clinical practice. Until now, physicians and diabetes educators rarely considered the timing of exercise when designing a physical activity plan for their patients. The accumulated evidence suggests that this criterion—known in the scientific literature as exercise timing—should be incorporated as another variable in medical consultations, along with the type of activity, its duration, and intensity. The International Diabetes Federation, in its physical activity management guidelines, also includes this evidence, noting that moderate to vigorous exercise in the afternoon and evening has a significantly greater impact on blood glucose control than morning exercise, and that it can help reduce insulin resistance. Most Recommended Types of Exercise: Specialists agree that combining aerobic exercise—such as brisk walking, swimming, or cycling—with resistance or strength training offers the greatest benefits for people with diabetes. The former improves insulin sensitivity through metabolic adaptations; The second increases muscle mass, which acts as a natural glucose reservoir and contributes to its uptake regardless of insulin levels.

A brisk 20- to 30-minute walk after dinner, or a light strength training session in the evening, could make a clinically relevant difference for those seeking to reduce their nighttime and morning glucose spikes.

Monitoring: If glucose is below 100 mg/dL before exercise, consume a small carbohydrate; if it is above 250 mg/dL, it is recommended to wait and consult a doctor.

Consistency: The greatest benefit is obtained by exercising regularly and at a planned time.

Precautions not to be overlooked

However,Experts warn that enthusiasm for the benefits should not lead to neglecting the risks. Hypoglycemia—a sudden drop in blood sugar—is a possible complication during or after exercise, especially in patients using insulin or certain oral medications. Therefore, it is essential to monitor glucose levels before, during, and after physical activity, and adjust insulin doses or carbohydrate intake in coordination with the treating medical team. Likewise, adequate hydration is essential: dehydration not only affects physical performance but can also raise blood glucose levels by triggering the release of stress hormones. And although nighttime exercise seems optimal from a metabolic standpoint, care must also be taken to ensure it doesn't interfere with sleep quality, since sleeping less than six hours or more than eight hours is associated with poorer control of glycated hemoglobin (HbA1c).