I wrote on this subject in Wellness World newsletter about 1995, for geriatrics in particular. Of course it is even more beneficial for the younger crowd. For most of us any amount of exercise is 100% better than none!

This is from  
Healthy Ways Newsletter  Issue 5-2, 2012 as edited and published by Dr. Bruce Fife, coconut research expert.
News Brief
Study: Even a Little Exercise Improves Health
Very modest doses of exercise, as little as 10-minutes a day, can be enough to measurably improve your health. These were the results reported in a study published in the Journal of the American Medical Association. The study’s researchers gathered their data by tracking the cardiovascular fitness of 464 overweight, sedentary, postmenopausal women as they followed a mild regimen of daily 10-minute sessions on exercise bikes and treadmills.

These findings seemingly contradict the prevailing view that longer, more intense workouts are needed to improve one’s health. However, the study’s author, Dr. Timothy Church, said these daily mini-sessions can lead to health benefits very quickly.
 Source:  “Boost for the Sedentary” by Delthia Ricks, Newsday.com.