Greater daily upright time was linked to differences in hip bone mineral density among older adults with obesity undergoing weight loss, depending on whether they wore a weighted vest, according to a secondary analysis of a randomized controlled trial published in Frontiers in Aging.
In the 12-month INVEST in Bone Health trial, community-dwelling adults aged 60 to 85 years with obesity or overweight with at least one obesity-related comorbidity were randomly assigned to weight loss alone, weight loss plus resistance training, or weight loss plus use of a weighted vest. All groups followed a structured dietary program targeting a 10% reduction in body weight over 12 months.
Participants in the weighted vest group were instructed to wear the vest for about 8 hours daily during their most active hours. The vest load was adjusted weekly to replace most of the weight lost, up to 10% of initial body weight. Participants were not given instructions about changing their sitting or standing time.
For this secondary analysis, researchers examined whether time spent upright — defined as standing or stepping — influenced changes in bone mineral density at the hip and spine. Upright time was measured objectively using a thigh-worn accelerometer at baseline, 6 months, and 12 months.
Among the 131 participants with sufficient bone scan data, average age was 67 years, about 70% were women, and average body mass index was about 34 kg/m². Participants spent roughly 5 to 5½ hours per day upright at baseline, depending on study group.
In the weight-loss-only group, a 30-minute increase in daily upright time was associated with a 2.4 mg/cm² decrease in total hip areal bone mineral density, whereas no significant association was observed in the weighted-vest or resistance-training groups.
No similar interaction was identified at the spine. Findings from computed tomography scans showed a similar directional pattern for trabecular bone at the hip, although results were exploratory.
Researchers suggested the findings may reflect the “mechanostat” principle, in which bone adapts to mechanical loading. During weight loss, reduced body mass may decrease skeletal loading; replacing some of that load with a weighted vest could help offset this effect. They noted that further studies are needed to determine whether encouraging upright time alongside vest use meaningfully preserves bone health.
The authors declared no competing interests.
Source: Frontiers in Aging