Numerous studies indicate that a person's lifestyle has a positive impact on their health. However, in spite of the predominant anti-health lifestyle, the average length of life in the past few decades has increased. What is the relation between a lifestyle and life expectancy? Does the lifestyle affect human life span? Epidemiological and prospective-retrospective studies were used to evaluate a 20-year long population-based experiment, which involved in-depth studies, analyses and evaluations of three related families who resided in the same community, had the same education level, and the same period of socialization and tradition. To evaluate the collected research material, the authors used their own: Scale for evaluating nutrition habits; Criteria to assess health behaviours of subjects; Criteria for diet assessment. The studied families led a similar lifestyle, with prevalence of anti-health behaviours. Theoretically, subjects should live a similar number of years. However, the length of their lives varied. Members of families with higher number of anti-health factors lived, in fact, longer. The authors confirmed the hypothesis that the lifestyle of the examined families was an important contributor to their health, but certainly it was not the only factor to determine their life expectancy. The length of lives of the examined family members varied despite a similar lifestyle.