Inactive people could cut their risks of premature death by up to 30 percent by adding as little as a brisk 20-minute walk to their daily lives, according to a study published this month in the American Journal of Clinical Nutrition.  The rate could also be decreased by engaging in any other brisk activities that would burn the equivalent of 90 to 120 calories.

Researchers at Cambridge University in England compared BMI, waist circumference and self-reported physical activity levels for the study of 334,000 Europeans.  All of the study subjects were placed in one of four categories based on activity levels: inactive, moderately inactive, moderately active and active.

Mortality rates dropped 20 percent to 30 percent in moderately inactive people compared to inactive ones. The improvements in mortality rates increased as the activity level increased for individuals with a BMI that was lower than 30 and for individuals with a waist circumference that did not put them in an abdominally obese category.

"If all inactive individual were at least moderately inactive, the number of deaths would theoretically be reduced by 7.5 percent," the authors of the study wrote.