That's the sobering conclusion of an American study in the current issue of the Annals of Epidemiology.
However, you don't have to become a marathon runner to lengthen your life. Even small amounts of physical exercise offer significant life-saving protection, while moderate and intense physical exercise provide only slightly more protection against dying, the study found.
Also, underweight people in this study were found to be at greater risk of dying from any cause than people of healthy weight.
The study is one of the first to examine body weight and physical activity at the same time, and compare their independent effects on the risk of dying.
The researchers examined data on physical activity and body measurements gathered between 1962 and 1965 from more than 9,000 men, aged 35 to 79. The men were ranked according to their activity levels and their body mass index (BMI), which reflects a weight-to-height ratio.
The study found the men in the lowest activity category had twice the risk of dying as men in the second-lowest activity category. The men in the lowest category had 38 percent more heart disease-related deaths than the men in the second-lowest activity category.
Men in the highest activity category lived the longest, regardless of their weight.
The study found that obese men (a BMI of 30 or more) had 33.6 percent more heart disease deaths than men with healthy weight. Overweight men (a BMI of 25 to 29.9) had 7 percent more heart disease deaths than those with healthy weight.
The U.S. National Institutes of Health has more about the health benefits of exercise.