Weight, diet and a lack of activity in adulthood are known to increase the likelihood of developing type 2 diabetes. New research using data from Swedish military recruits shows that fitness and strength as a teen can also predict diabetes in later life.

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Fitness and strength in youth might help prevent diabetes in adulthood.

Diabetes is one of the most pressing health issues of the Western world. From 1980-2014, the number of newly diagnosed diabetic adults tripled in America.

In some states, including Alabama and Kentucky, more than 10% of adults have had a diabetes diagnosis in their lifetime.

On a global scale, diabetes, often a preventable disease, affects 300 million people.

These rather terrifying figures have spurred furious research into the factors that bring diabetes to the fore. Any nuggets of information that might help stem diabetes’ advance are sure to be investigated to the fullest.

Research has already shown that risk factors for type 2 diabetes (the most common form by far) include weight, inactivity, family history, race, age and high blood pressure. However, the role of fitness (rather than a lack of fitness) has not been investigated to the same degree.

Research published this week in Annals of Internal Medicine adds evidence to the theory that physical fitness in youth, regardless of weight, might increase the chances of diabetes later in life.

The research team, led by Dr. Casey Crump, used data obtained from Swedish military conscripts. More than 1.5 million young men were included in the analysis.

The 18-year-olds were subjected to standardized tests measuring their aerobic capacity and muscle strength; they were followed through to a maximum age of 62. This study is one of the first to use such detailed, objective measurements of fitness – aerobic capacity and muscle strength – rather than self-reported levels of activity.

The team found that, regardless of the recruit’s weight, socioeconomic class or family history, lower cardiorespiratory fitness and muscle strength raised the risk for type 2 diabetes.

Medical News Today asked Dr. Crump what mechanisms he believes might be at work to produce such a marked effect over the decades. He concedes that the factors are likely to be incredibly varied, and this is just the first step on the path to understanding. Dr. Crump said:

Individuals with low fitness early in life may also be more likely to have unhealthy lifestyle factors as adults, which contribute to the increased risks we observed.”

He goes on to outline the types of study that will need to be carried out to unravel cause and effect; studies that “measure physical fitness as well as diet and BMI at other time points across the lifespan” will be necessary to observe which age groups are particularly susceptible.

The paper goes on to discuss some of the theories that might explain the mechanisms by which fitness and strength help to stave off type 2 diabetes. Aerobic activity is known to increase mitochondrial density, the powerhouses of the cell; it also boosts the activity of oxidative enzymes. Both of these processes enhance the breakdown of fatty acids and improve insulin sensitivity.

Strength training enhances muscle fiber growth, which increases glucose use and might enhance insulin’s responsivity. Additionally, both strength training and aerobic exercise help reduce the amount of fat stored in the body; this is already a well-known risk factor for type 2 diabetes.

These recent findings demonstrate a clear and present need to keep the youth of America fit. They are not the first results to illustrate the importance of keeping physically fit in youth, but they are the first to show that a level of fitness is important regardless of weight.

MNT asked Dr. Crump whether public projects focused on adolescent health could play an important role. Although there are countrywide programs already in existence, such as the Presidential Youth Fitness Program, much more needs to be done. Dr. Crump said:

The current physical activity guidelines for children and youth recommend 60 minutes of exercise daily. […] Currently, only about half of US children and youth meet these guidelines.”

The study makes for fascinating and concerning reading. Dr. Crump plans to continue looking into these early factors and their potential roles in heart disease, stroke and premature death. No doubt the picture will slowly become clearer.

Diabetes is a multifaceted and complex illness; MNT recently covered research that investigated the role of gut bacteria in type 2 diabetes.