Nutritional Pearls: The Importance of Youthful Fitness

Jonathan is an 18-year-old high school graduate preparing to move away to college. At his most recent check up, he expresses concern about his body mass index. He was involved with several sports at his high school and has a highly active lifestyle. However, he has a BMI of 28 and is concerned about how it may affect his health in the future.

How do you advise your patient?
(Answer and discussion on next page)

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Answer: Greater physical fitness early in life may help protect you from type 2 diabetes later on.

It's well established that being having a body mass index in the overweight or obese range, in and of itself, puts you at greater risk of diabetes and its life-altering complications, including heart disease, high blood pressure, stroke, and death. That said, even those overweight or obese persons who do not develop the common complications of obesity are still at greater risk of death from all causes. On the other hand, recent research looking at actual body fat—as opposed to body mass index, which is an indirect measure of adiposity—showed that those with a normal body mass index but high levels of body fat were 19% more likely to die of any cause than those with the lowest levels of body fat.
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Clearly, the health risks of one's weight are more complicated than simply the number of pounds carried on their frame. A team in Sweden noted this and sought to look at whether physical fitness levels might have an effect on an individual’s risk of diabetes, independent of body weight.

The Research

They made use of records kept by the Swedish government, which, until 2010, required military service from all Swedish men at age 18. Between 1969 and 1997, over 1.5 million men received a military conscription examination, a 2-day standardized physical and psychological exam that included measurement of aerobic capacity (measured while using a stationary bicycle) and muscle strength (measured for knee extension, elbow flexion, and grip strength).

With records maintained by the Swedish Hospital Registry and the Swedish Outpatient Registry, the authors were able to identify those men who developed type 2 diabetes after the initial military examination and compare their aerobic fitness and muscle strength at age 18 with those who did not.

The Results

Those men with both the lowest aerobic capacity and the lowest level of muscle strength were 3 times more likely to develop type 2 diabetes, regardless of their body mass index, family history, or socioeconomic status, than those with both the highest levels of aerobic capacity and muscle strength. Those with the highest aerobic capacity and the lowest level of muscle strength, however, were only 58% more likely to develop type 2 diabetes.

What’s the “Take-Home”?

This study does not say that if you are in good shape at 18 you have nothing to worry about, as it doesn't take the participants' body weight or later level of fitness into account. It does suggest, however, that greater physical fitness early in life, especially aerobic fitness, may help protect you from type 2 diabetes later on. Just how that might happen—whether those who are fitter early in life are more likely to maintain their fitness, follow a healthy diet, or are simply luckier—is not clear.

Reference:
Crump C, Sundquist J, Winkleby MA, Sieh W, Sundquist K. Physical fitness among Swedish military conscripts and long-term risk for type 2 diabetes mellitus: a cohort study. Ann Intern Med. 2016;164(9):577-584.