Twenty five centuries ago the Greek philosopher Hippocrates wrote in Regimen in Health

Eating alone will not keep a man well; he must also take exercise. For food and exercise, while possessing opposite qualities work together to produce health.

There are multiple risk factors that influence health and disease.  Research has shown that inactivity is the greatest predictor of mortality, especially in women:

What is most surprising is that inactive women are 2.23 times more likely to die than overweight women (relative risk 2.1 versus 0.94).

How much activity do you need?

The chart below also shows the highest risk of death is found in people who are inactive. When someone burns up over 3,000 calories per week the chance of death decreases by 54%. Interestingly, burning up more than  3,500 calories per week carries a 35% higher risk than exercising between 3,000-3,499 (still with a decrease of 38% over those who are inactive):