The (Digestive) Power of an After-Dinner Walk

Did your parents ever warn you not to go swimming right after you ate? It always seemed like oddly specific advice from the people who fed us bologna sandwiches and kicked us outside for unsupervised play all summer. But at the local pool, everybody’s mom and dad became an expert in the dangers of swimming and undigested food.

Thing is, they were right. Digestion and exercise are like opposing teams on the football field— each competes for control of physiological resources, namely energy and blood flow. When we’re digesting a meal, blood flow to the stomach and intestines increases. When we exercise, blood flow to our muscles increases. Since we’re not constantly increasing our total blood volume, this means that our body must prioritize one process over the other. If I’ve just eaten Thanksgiving dinner, my body focuses on breaking down all that turkey and sweet potato pie. (This is also why we get sleepy after a big meal.) But if I’m sweating through a BODYPUMP class, the focus is on my working muscles. Trying to do both at the same time can lead to cramping, nausea and other GI distress.

This is most likely where the one-hour-after-eating swimming rule started. If you get a sore stomach in aerobics class, you can just stop, but if you’re out in the deep end of the pool, it might be too difficult to swim to the edge when your stomach starts cramping. And drowning due to bologna-sandwich intake is just no way to go.

But it’s not all spy vs. spy—after all, without digestion, we wouldn’t get the energy we need for exercise. And the truth is, exercise has many positive effects on our digestion. What’s surprising is how many of them we can get from a simple after-dinner walk.

Feel less hungry and eat less

We’ve all heard that regular exercise can help “regulate appetite,” but have you ever wondered what that means? For starters, it means that becoming more physically active in general helps us feel less hungry and eat less at mealtimes. It gets even more interesting when we look at specific forms of training. Resistance training, for instance, doesn’t decrease appetite but—curiously—does decrease the amount of food we eat afterward.

But brisk walking is the real superstar because it manages to avoid triggering what researchers call compensatory responses . That is to say, when we burn energy during a one-hour walk, we don’t seem to feel hungrier or eat more to make up for the energy expended during the walk. Which officially makes walking a weight-loss secret weapon!

Walking gives our stomachs an assist

It takes an average of four to five hours for a meal to exit our stomachs completely. But this gastric emptying time varies a lot, depending on what we ate and who we are. Protein and fiber-filled meals, for instance, take longer to digest than simple carbohydrates (like a glass of juice). Men digest significantly faster than women on average. And digestion is slower for women in the follicular phase of their menstrual cycle compared with when they’re in the luteal phase. It’s even related to non-food lifestyle choices—smokers digest more slowly than nonsmokers.

Many cultures share the tradition of an after-dinner digestif of some kind, be it espresso or grappa, to help digestion. But a 2008 study found that most after-dinner traditions actually slowed down digestion, with the exception of one: The humble after-dinner walk was the only after-dinner tradition that accelerated gastric emptying. It’s also been shown to reduce the glycemic effect of a meal, meaning it helps us prevent spikes in our blood sugar levels.

Walking helps our movements move

Peristalsis is how digested food and waste move through our intestinal tract. Our intestines contain a layer of muscle that contracts rhythmically to squeeze food along. “The movement pushes food and liquid through your GI tract and mixes the contents within each organ,” the National Institutes of Health states. “The muscle behind the food contracts and squeezes the food forward, while the muscle in front of the food relaxes to allow the food to move.” And all without us thinking about it for a second.

But what’s truly amazing about these muscles is how normal they are—just like every other muscle, they respond to our physical activity levels. This means that exercise doesn’t only give us strong abs but also gives us strong intestines. And well-toned intestines help us ward off constipation and other lower-GI troubles. Of course, sometimes stress can be the cause of digestive upset, but we’ve got you covered there, too—these breathing exercises will normalize the nervous system and help the digestive tract de-stress.

Video credit: gpointstudio, Adobe Stock
Photo credit: monkeybusinessimages, Thinkstock; Rawpixel, Thinkstock; Photology1971, Thinkstock; Jamie Street, Unsplash