Aging in the 21st century.

In this introductory article, a rapid overview is presented of the recent increase of life expectancy and its limitations mainly by unhealthy living habits: overeating, fast food, lack of exercise. The strong increase of obesity worldwide with its metabolic consequences might well limit or even decrease human life expectancy. The part of the population over 65 who have access to "anti-aging medicine" represents however another challenge to experimental and clinical gerontology, further discussed in later articles of this issue.