WALKING AFTER A MEAL: ITS EFFECT ON BLOOD GLUCOSE CONTROL

By: Edrick Purnomo Putra

Walking is a form of physical activity that can be easily done by most people. It is a part of our daily life and does not require specific equipment or a special environment. Walking has become popular as a form of physical activity to gain health benefits, even leading to the well-known recommendation of 10,000 steps daily. However, a recent study shows that it does not have to be 10,000 steps per day to be healthier. A meta-analysis published in 2022 provides an evidence-based threshold for the optimum number of steps per day associated with lower all-cause mortality risk, which varies by age. This is the first study to do so, including a total of 47,471 adults and 3,013 deaths from 15 studies across Asia, Australia, Europe, and North America. Mortality risk progressively reduced with around 6,000-8,000 steps per day in adults aged 60 years or older and 8,000-10,000 steps per day in adults under 60 years old.

While the studies showed evidence about the number of steps, timing might also play an important role. It is true that “every move counts,” just like WHO’s latest recommendation on physical activity, but timing might make a bigger impact on our health, especially in controlling blood glucose levels. Blood sugar will increase after every meal, reaching its peak 30-60 minutes after a meal and later dropping to its lowest 2-3 hours after a meal in healthy humans. These blood sugar spikes, or repeated post-prandial hyperglycemia, cause hyperinsulinemia, which can contribute to insulin resistance over the long term. This is detrimental to our health, especially for people with diabetes mellitus, those at risk of diabetes, and those with obesity. Exaggerated blood glucose spikes increase oxidative stress, endothelial dysfunction, pro-inflammatory factor levels, and the risk of developing cardiovascular pathologies. Post-prandial hyperglycemias also interfere with long-term glycemic control, marked by elevated glycated hemoglobin (HbA1c) levels. These glycemic exposures put diabetics at risk of cardiovascular disease, including micro and macrovascular complications. In healthy humans, glycemic excursions, even in the non-diabetic range, pose a relevant risk of low-grade inflammatory and cardiovascular diseases. Therefore, suppressing postprandial hyperglycemia and maintaining long-term glycemic control is crucial.

One effective way to manage hyperglycemia is to engage in physical activity close to food intake. Research has been conducted to determine whether physical activity done before or after a meal is more beneficial. A study with type 2 diabetes patients compared a single bout of 20 minutes of self-paced treadmill walking done immediately before a meal and 15-20 minutes after a meal. Postprandial walking appeared to be more effective in controlling glycemic impact in evening meals compared to premeal or no exercise. Another study with type 1 diabetes patients using hybrid closed-loop delivery systems (HCLS) compared a single bout of 20 minutes of self-paced walking done within 30 minutes before dinner and 30 minutes after dinner. This study suggests that premeal walking may be more effective at attenuating blood glucose levels after dinner compared to postmeal walking in type 1 diabetes patients with good glycemic management using HCLS.

Walking after a meal is proposed to prevent a rise in blood sugar because walking consumes blood sugar. Studies have discussed whether exercise should be performed directly after a meal or after a certain time. A case report with two Japanese elderly women showed that walking after a meal flattened the blood sugar curve and resulted in weight loss after a month of walking right after meals. A meta-analysis released in 2022 concluded that walking has a greater effect on postprandial hyperglycemia attenuation when undertaken directly after a meal compared to after a longer interval or before a meal. Some people might feel discomfort while walking directly after a meal; however, for those without such problems, walking directly after a meal brings no adverse events. Moreover, a study showed that 10-15 minutes of slow walking after a meal could be effective in relieving bloating due to abdominal distention.

It is clear that physical activity in the form of walking can be a potential part of diabetes management. A study in New Zealand compared different walking timings in patients with type 2 diabetes. Patients were divided into two groups: one group was advised to walk 30 minutes each day, and the other group was advised to walk 10 minutes after every meal each day, starting within 5 minutes after finishing the meal. This study showed that even though both groups fulfilled the current physical activity recommendation, patients who walked after meals daily had better improvements in postprandial hyperglycemia compared to those who walked at unspecified times. It was also discussed that postprandial activity might avoid the need for additional total insulin dos-es or mealtime injections. Therefore, the study recommended at least 10 minutes of walking after every meal, especially meals with high carbohydrate content. Another study on the elderly at risk for impaired glucose tolerance compared 15-minute bouts of walking after every meal performed 30 minutes after each meal with a single bout of 45 minutes of walking at different times. This study concluded that both sustained morning walks and postmeal walks significantly improved 24-hour glycemic control. However, postmeal walks were significantly more effective in reducing 3-hour postprandial blood glucose levels. Therefore, short intermittent bouts of walking after a meal were effective in controlling postprandial hyperglycemia in the elderly.

An interesting meta-analysis published in 2022 made interesting comparisons of prolonged sitting to intermittent standing breaks and intermittent walking breaks. This study revealed that intermittent standing breaks significantly improved postprandial blood glucose levels compared to prolonged sitting. While light-intensity walking showed a superior effect in attenuating postprandial hyperglycemia and insulin levels, this study showed that standing can still be a beneficial form of physical activity for glucose control compared to being sedentary.

Walking can be done indoors or outdoors, but some people might be reluctant to get out of the house to walk or may live in limited spaces that prevent them from walking around the house. Spot marching or walking in place can be a safe and feasible alternative for individuals with such problems. A study in Thailand compared post-meal spot marching exercise with standard treatment in type 2 diabetes patients. In the intervention group, patients were asked to do 3 sets of 15-minute spot marching after a meal per day, 4 times per week, for 8 weeks. The movements included shoulder flexion ≥90° and hip flexion ≥70° with an 80-90 beats per minute rhythm. The study concluded that spot marching after meals can be a home-based exercise to improve glycemic control, demonstrated by improvements in HbA1c. Moreover, it also improves exercise tolerance, leg muscle strength, and quality of life in patients with type 2 diabetes.

In diabetes management guidelines, initiating basal insulin is recommended for type 2 diabetes patients who fail on oral hypoglycemic drugs. When the HbA1c target is not yet achieved, controlling post-prandial hyperglycemia is advised. Using rapid-acting insulin or GLP1 agonists in combination with basal insulin or switching to premixed insulin are options; however, these options require the patient to have multiple injections daily. Moreover, GLP1 agonists are not cheap and also come with gastrointestinal side effects. Therefore, physical activity after exercise could be a better option. A study in Thailand compared post-meal walking with standard medication treatment in type 2 diabetic patients who failed basal insulin by comparing one prandial insulin injection and post-meal walking on glycemic control. Patients were asked to walk as fast as possible for 15-20 minutes after at least one meal per day, every day. The study concluded that there were no significant differences in HbA1c and fructosamine reduction between the post-meal walking and prandial insulin groups after 6 weeks. Although post-meal walking might be as effective as prandial insulin, the magnitude of reduction was small; therefore, a longer study with a bigger sample size and different walking protocols is still needed in the future.

Walking causes muscles to contract. After a meal, with blood sugar rising, insulin will also rise. Both insulin and muscle contraction will stimulate the translocation of the GLUT4 transporter protein on the cell membrane of muscle. Muscle contraction itself will start glucose uptake without relying on insulin; thus, exercise can help insulin in people with aging-related reduced insulin secretions and those with insulin resistance. Increased GLUT4 translocation of glucose on the plasma membrane during muscle contraction also contributes to the decrease in HbA1c in type 2 diabetic patients.

Walking after a meal has a significant impact on our health, especially in attenuating blood sugar levels. However, the important thing to note is not just about the number of steps or the timing, but to consider the latest recommendation on physical activity. The 2020 WHO Guidelines on Physical Activity recommend all adults to do at least 150-300 minutes of moderate-intensity or 75-150 minutes of vigorous-intensity aerobic physical activity per week. It is also recommended to do moderate or greater-intensity muscle-strengthening exercises on 2 or more days per week. Recommendations for people with diabetes are not far different, yet special considerations need to be made, and consultation with sports medicine specialists should be sought. In the end, walking is just a form of physical activity, and with perfect timing, we can optimize its health benefits. So next time after you finish your meal, don’t forget to stay active and move to lower your blood sugar.

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