Researchers studied the data of 1.5 million Swedish men examined over several decades. They found that 18-year-olds demonstrating a combination of low aerobic fitness, measured by the ability to sustain cycling on a stationary bike, and high body mass index (BMI), measured from weight and height calculations, were at greater risk of developing ischaemic heart disease later in life.

Obesity and a sedentary lifestyle are two of the biggest enemies of human health, but their interactive effects on the body are not all that clear. Past studies have shown that regular physical activity can help reduce the risk of developing chronic diseases, but it hasn’t been clear if exercising early in life can have an impact in adulthood.

Casey Crump at Icahn School of Medicine at Mount Sinai, New York, and co-workers examined the interactive effects of obesity and physical fitness on the risk of ischaemic heart disease (IHD). They examined the data of approximately 1.5 million Swedish men who underwent compulsory physical examinations prior to military conscription between 1969 and 1997, and checked whether their body height, body mass, muscular strength and aerobic fitness had any influence on IHD risk later in life. After adjusting for family history and socioeconomic factors, they found that people who had low aerobic fitness and high BMI at age 18 were more likely to develop IHD in adulthood.

Of the 1.5 million men in the cohort, approximately 2.5% were diagnosed with IHD by 2012. The researchers found that those with low aerobic fitness at 18 were 1.8 times more likely to develop IHD than those with high aerobic fitness. Also, men with high BMI when young were 1.8 times more likely to develop IHD than those with normal BMI. Surprisingly, muscular strength had no significant impact on IHD risks.

The results show that aerobic fitness and BMI in late adolescence are the two biggest risk factors for IHD in adulthood. Exercising, eating well and keeping an eye on body weight early in life might offer long-term protection for the heart and longevity.

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