According to the American Diabetes Association (ADA), aerobic exercise — such as walking — has a range of health benefits. Exercise lowers your risk of heart disease and improves insulin sensitivity. In fact, regular physical activity (unless your healthcare provider advises against it) can lower your blood glucose levels and reduce the risk of type 2 diabetes (T2D) by up to a staggering 58%. But if you want to reap the benefits of walking, should you do it before or after eating a meal? Research suggests the answer could be both, depending on each individual person. Some recent research points to metabolic benefits (including glycemic control) being higher when you’re in a fasted state before exercising. Then again, if you tend to experience a blood glucose spike after eating, hydration and walking after eating can help lower that spike.
Why your blood sugar levels matter
Your organs and tissues receive the nutrients you need through your bloodstream. As you eat, food is digested into simple molecules such as glucose, which is absorbed into your bloodstream and increases blood glucose (i.e., blood sugar) levels. As blood sugar levels rise, the pancreas produces a hormone called insulin. If you have too much blood sugar for a prolonged period, your cells eventually stop responding to insulin, resulting in type 2 diabetes. Monitoring your blood sugar levels and how they respond to different activities — such as eating, sleeping and exercise — can help you identify the best combination of habits for getting your blood sugar levels under control.
Benefits of exercising after eating
We know that exercise provides us with many health benefits for our bodies and minds. But is it good to walk after eating, and does the time we exercise around a meal matter? The research suggests so, particularly when it comes to our blood glucose levels.
- A 2016 review of 39 eligible studies, 5 of which examined energy expenditure 30 minutes after a meal, showed that performing light aerobic exercise for an hour stops blood glucose levels from going too high without losing too much blood sugar. Although this study was done on people diagnosed with a metabolic disorder, healthy patients also had similar benefits.
- A 2021 review of 51 eligible studies showed that a single bout of continuous aerobic exercise at least 30 minutes long decreased glucose and insulin levels in the 6 hours after eating a meal. These studies were performed on healthy adults.
In summary, the body of research tells us that you might be able to better manage your blood glucose levels by exercising soon after eating a meal. However, you have to account for the meals given to the study participants. Different meals have different nutrient compositions from the standardized meals typically provided in research studies. The foods in these meals impact how quickly and effectively your body absorbs the nutrients and alter blood glucose levels. Knowing how much the benefits of exercise extend with different kinds of meals will help refine meal plans that maximize your health.
But what about walking after eating a meal?
There’s an old saying that you should wait at least 30 minutes after eating before you swim, lest you drown. The myth stems from the mistaken belief that all your blood and oxygen goes to digestion. While walking isn’t swimming, it’s true generally that stomach cramps can arise from exercising too soon. However, in any case you have enough blood to keep your body parts working. In fact, having a leisurely stroll after dinner has distinct metabolic benefits.
- A 2009 study of 12 elderly type 2 diabetes patients showed that walking after eating a meal was better for minimizing the glycemic impact of a meal than walking before eating a meal.
- A 2019 randomized controlled trial (RCT) determined that low- to moderate-intensity activity immediately following breakfast reduced the maximum blood sugar concentration after a meal and fluctuations in sugar concentrations in blood. Conversely, pre-breakfast activity or delayed post-breakfast activity had little impact on both parameters.
Unfortunately, the population sizes in these studies were small, making it hard to draw clear conclusions about walking after eating; but the preliminary indication is that movement not long after eating has distinct metabolic benefits.
Benefits of exercising before you eat
There are also plenty of benefits to be had from exercising before a meal. Brief bursts of intense exercise before a meal can control blood sugar levels better than a single 30-minute session of moderate exercise among people with insulin resistance. A more recent meta-analysis done in 2016 showed that insulin levels fluctuated far more when exercising after a meal than before a meal. When you exercise before a meal, you may later become more able to process the sugars ingested as nutrients.
Exercising before eating a meal also provides other benefits beyond improving your ability to use the sugars entering your bloodstream after a meal:
- Improved fat oxidation: Fat oxidation refers to the process of breaking down the fatty acids stored in cells that store fat in our bodies. These cells are called adipocytes. The same 2016 meta-analysis discussed earlier showed that people who exercised before eating a meal had a higher fat oxidation rate than those who ate before exercising.
- Increased aerobic performance: Aerobic performance includes activities such as brisk walking, jogging and sprinting. A 2018 meta-analysis of 46 studies determined that fasted exercising (or exercising before you eat) bolsters prolonged aerobic activities compared with after-meal exercising. This coincided with increased free fatty acid concentrations in the blood to be used as fuel following exercise.
- Modified metabolic signalling: Your body responds to changes in blood sugar concentrations through diverse signalling pathways. These pathways tell cells to change how much glucose they take in at a time. One such system, the SIRT1 signalling system, when activated, controls diverse cellular processes such as insulin sensitivity that can help your body respond optimally to changes in blood sugar levels. Not eating a meal before exercising has been observed to increase SIRT1 expression compared with those who had a meal before exercising.
The potential, relative benefits to exercising before and after a meal depend on many variables. For instance, the pluses of exercising around a meal could come from differences in how the experiments were set up and the characteristics of the people participating in the studies. The number of volunteers participating across the studies was fairly low, as well. The benefits procured from altered signalling are also more complex. We previously covered a different 2018 study that studied elderly men with obesity who ate before a meal. The adipocytes in those participants had altered gene expression which the authors state would “blunt the health benefits of regular exercise.” More research is required to tease out these impacts further.
Is it good to walk after eating? There are many lifestyle modifications that you can make to benefit your health. Exercise is certainly an important one. Exercising after a meal may help prevent glucose levels from going too high after ingesting food. On the other hand, exercising before a meal increases the amount of fat you break down in your body and may alter how your metabolism responds to food consumption later in the day. Thus, ideally, you’d gain the most by exercising before and after eating a meal. Sounds hard to accomplish? Not necessarily: if you’re realistic and plan for a short work-out pre-meal and then a more leisurely walk post-meal, you might just be doing your health a big favor. As an added aid, try using a continuous glucose monitor and the January app to keep track of your health today. Should you still have trouble keeping your blood sugar levels under control, speak with your doctor about further steps you can take to better address your metabolic health.