Of all interventions for osteoporosis as an overt lifestyle-related disease, primary prevention is given first priority, where gaining beneficial lifestyle habits during younger years leads to acquisition of maximum bone mass. Clear increases in bone mass are seen before the age of 18 years, with the increases being most conspicuous from 10 to 14 years of age, the time of onset of menarche, during which, for individuals in adequate nutritional status, vertical load exercises are the most efficient of all approaches in ensuring acquisition of maximum bone mass. After the young adult mean (YAM) has been attained between 20 and 44 years, the focus in primary prevention is shifted to prevention of bone mass decreases, in which high bone mass acquired through beneficial diet and exercise habits during younger years helps to delay the onset of osteoporosis even in advanced age.