Final answer:
The most common effect of activity upon later life is the slowing down of bodily deterioration, leading to a healthier aging process, greater life expectancy, and improved mental and social well-being.
Step-by-step explanation:
According to research, the most common effect of activity upon later life is the ability to slow down the deterioration of the body that comes with old age, contributing to healthier aging. Regular exercise and healthy lifestyle choices can reduce mortality rates and extend life expectancy. For example, engaging in physical activity that meets or exceeds the U.S. Department of Health and Human Services guidelines results in significant gains in years of life. Additionally, social involvement and mental activities are crucial for maintaining a sense of contentment and fulfillment in later years, contributing to an active and satisfied elderly population.