Increased Fat Mass Leads To Bone Loss, A Prospective Short-Term, 18-Week Study In Young Healthy Men Undergoing Basic Training of The Swiss Army

Background: Quantitative ultrasound (QUS) methods have been widely used to assess bone status in osteoporosis. For follow-up examinations, there are no recommendations regarding the use of QUS due to a lack of data. This study aimed to investigate the longitudinal use of QUS in 4 months of military training to assess bone remodelling in association with physical activity and anthropometry.Subjects and methods: We analysed the changes in bone health using calcaneal quantitative ultrasound (Sonost-3000) as well as the impact of anthropometry, body composition, and physical activity in young men at the start (n=104) and 18 weeks later after basic training (n=73).Results: After basic training, the subjects were heavier, slightly taller, and had higher fat mass and grip strength. An overall decrease in physical activity and bone ultrasound attenuation (BUA) was observed. A negative correlation between the development of fat mass and physical activity with BUA was found, with fat mass as the highest impact factor. Development of grip strength correlated positively with SOS, while skeletal muscle mass and waist circumference correlated negatively. Development of skeletal muscle mass and weight had the highest impact on SOS.Conclusion: Overall, subjects were heavier, taller, and fatter and showed increased grip strength, decreased physical activity, and loss of bone health. It is alarming that the increase in fat mass already has a negative effect on the bone structure after 18 weeks. As seen in other studies, the impact of force on bone during walking is insufficient to strengthen it. The results imply that the selected troops of the Swiss army recruits (air defence) have too little high-impact physical activity during their basic training, what should be changed in the future. To verify the worrying results from our study, a prospective randomized study with a survey of low and high impact activities as well as a detailed survey of eating and nutritional habits during basic training should be carried out. QUS seems to be a good tool for assessing bone status, even in the event of short-term changes.