While some people play sports to keep in shape, others just enjoy feeling active and exhausted. What happens in our bodies when we exercise, and how does that make us any ‘healthier’? To find out, I talked to Professor Matthijs Hesselink, an expert on the health effects of exercise.
What’s the difference between exercise and sports?
“Sports refers to an intense workout, whereas exercise includes any break of sedentary time – like riding your bike, walking through the city, up the stairs, etc. Exercise means you’re moving, keeping your body active, without creating an after-sport (physical and mental) craving for food or compensatory resting. It’s easier to integrate in everyday life, and in a way it’s what we’ve ‘evolved’ to be good at. As (slow) hunters and gatherers, we’re equipped to sustain long periods of low availability of food and prolonged low-intensity exercise.”
Students tend to think of sports as a means to lose weight – and thus be healthier. What do you think about that?
“Say you run for half an hour, five kilometres. If you weigh 70kg, this burns around 350 kcal [rule of thumb: 1kcal x km x kg –Ed.]. But it leaves 23.5 hours of the day to sit and eat. And don’t forget: people tend to ‘reward’ themselves after doing sports – immediately replenishing the energy they burned.”
So exercise is better to lose weight?
“The energy burned during exercise or sports is rather limited, compared to the amount of energy we can (easily) overeat. Only 250 kcal too much a day will make you obese within 10 years. A little sports or exercise can counterbalance that and prevent weight gain. But losing weight through sports is difficult. You have to be quite active in your everyday life to achieve that. Of course it’s beneficial for overweight people to lose weight. But regular sports or exercise is also beneficial for people of normal weight. In addition to its positive effects on social life and mental health – lower risk for dementia and Alzheimer’s – it improves metabolic health.”
“Trained tissue, like muscles and organs, makes better use of the substrates provided in our diets. Our bodies need glucose and fatty acids to produce ATP, the global energy source in the cells of our bodies. After a meal, our blood is flushed with glucose (in carbohydrate-rich meals) and fatty acids (in fat-rich meals). For our bodies to run smoothly, it’s vital that both substrates maintain a healthy balance. Insulin is an important player in regulating that. Exercise improves the body’s insulin sensitivity. This means our bodies get better at clearing the blood from excess substrates, which leads to reduced blood sugar, lower risk for damage to blood vessels (and thus for heart- and brain-infarctions), higher cardio-respiratory fitness (being able to walk up the stairs without getting breathless), reduced resting heart rate and a better response to foods that are high in carbohydrates and fat.”
What would you advise when it comes to food intake?
“About 10 percent of your daily energy expenditure is required for the processing of food. 50-70 percent is necessary for the daily maintenance of our body – our ‘basal metabolism’. This amount, contrary to what people think, is quite steady across different people of similar physical stature; you can’t blame a ‘slow metabolism’ for being overweight. The only thing we can really work with is the energy spent during physical activity – the more physical effort we make, the higher our energy expenditure.”
Given the current obesity epidemic, this would seem to be important.
“I think it’s far more impressive that not more people are obese. The energy balance in our bodies is very tightly regulated – I think our bodies are doing an excellent job at keeping everything in balance throughout our lives.”