This study shows that avoiding an accumulation of excess fat tissue is more beneficial than physical fitness when it comes to long term health, as measured by reduced risk of suffering heart disease. This seems plausible based on a survey of data gathered in various mouse studies on fat, exercise, and life span. Calorie restriction and even surgical removal of visceral fat extend maximum life span while exercise only improves healthspan. The best bet is to be both fit and lean, of course:
[Researchers] analysed data from 743,498 Swedish men who received a medical examination at the age of 18 when they were conscripted into national service from 1969 to 1984. The men's fitness level was measured with a bicycle test in which the resistance was gradually increased until they were too exhausted to continue. The men were monitored for an average of 34 years until they suffered a heart attack or died or until 1 January 2011, whichever came first.
The study shows that being physically fit in your teenage years reduces the risk of a heart attack later in life. Fit but overweight or obese men also ran a significantly higher risk of suffering a heart attack than unfit, lean men. "While being physically fit at the end of your teens can reduce the risk of heart attack, fitness alone does not appear to fully compensate for the risks with being overweight or obese. In other words, having a normal weight is more important than being in good physical shape, but it is even better to be both fit and have a normal weight."
The study shows that with every 15% increase in physical fitness, the risk of suffering a heart attack 30 years later is reduced by around 18 percent after factoring in different variables such as socioeconomic background and Body Mass Index, BMI. The results also indicate that regular fitness training late in your teenage years is consistent with a 35% lower risk of a premature heart attack.