DEAR DOCTOR K:
My teenage son doesn’t like sports or exercise. Diabetes runs in our family. You say exercise protects against diabetes and is valuable even in young adults. Can you give me some ammunition to convince my teenager to exercise?
Perfect timing: A new study has been published that provides an answer. Most studies of exercise have been in adults, often older adults. Until this recent study, there wasn’t a lot of information about teenagers.
The new study looked at 1.5 million teenage men enlisted in the military in Sweden between the years 1969 and 1997. None had diabetes at the time they entered the military. Because military service is required in Sweden, these young men included over 97 percent of all Swedish men aged 18. Health records were available for all the men, for up to the next 40 years.
At the time they entered military service, their aerobic capacity, a reflection of the amount of aerobic exercise, was measured. So was their muscle strength, a reflection of the amount of strength or resistance training. Medical records over the next several decades also identified which of the young men developed diabetes (the common type, called Type 2 or “adult-onset” diabetes).
The research team then could compare the young men who were the least fit to those who were the most fit, with regard to the rate with which they developed Type 2 diabetes many decades later. Those who were the least fit (both in terms of aerobic capacity and muscle strength) were more than three times more likely to later develop diabetes.
This connection between fitness and reduced risk of diabetes was true regardless of how much the teens weighed when they began military service. That’s important because exercise helps to reduce weight, and lower weight helps to protect against diabetes. This study shows that exercise in teenagers — both aerobic exercise and strength training — reduces the risk of diabetes in later life, even if the exercise hasn’t led them to achieve a healthy weight.
Aerobic exercise and strength training cause several different chemical changes in muscle. These changes cause muscle to extract sugar from the blood more efficiently. That, in turn, lowers blood sugar levels. Regular exercise also shrinks the size and number of fat cells. This leads to hormonal changes that reduce the risk of developing diabetes.
A weakness of this study is that it did not measure again, later in life, the aerobic capacity and muscle strength of these young men. It is theoretically possible that the ones who exercised the most as teens continued to exercise the most as older adults. In other words, maybe the exercise when they were teens didn’t protect them, only the exercise later in life. That’s possible, but I think it’s more likely that regular exercise in teenage and young adult years protects against diabetes many years later.
I hope that’s the ammunition you need. It should be — if your son is a rational teenager. But I know that rational teens can sometimes be hard to find!