Several studies that used DXA or quantitative ultrasound suggested that objective ly measured SB was negatively associated with lower extremity bone outcomes , such as femoral neck bone mineral density .
The magnitude of this negative association was small and independent of moderate-to-vigorous physical activity .
In contrast to the lower extremities , there was insufficient evidence for an association of lumbar spine bone outcomes with objective ly measured SB .
In high- quality studies that used DXA , no association was observed between objective ly measured SB and total body bone outcomes .
In studies using question naires , none of these relationships were observed .
Sedentary  behaviour ( SB ) is increasing in Western societies and some studies suggest a deleterious effect of SB on bone .
The aim of this systematic review was to examine the association between  SB and bone health in children , adolescents and young adults .
Adiposity and TV viewing are related to less bone accrual in young children.
OBJECTIVE To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospect ively for 4 years , with a focus on the role of physical activity and TV viewing . STUDY DESIGN Children were part of a longitudinal study in which measures of fat , lean and bone mass , height , weight , activity , and diet were taken every 4 months from ages 3 to 7 years . Activity was measured by accelerometer and TV viewing by parent checklist . We included 214 children with total body dual energy x-ray absorptiometry ( Hologic 4500A ) scans at ages 3.5 and 7 years . RESULTS Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years ( P < .001 ) . More TV viewing was related to smaller gains in bone area and bone mass accounting for race , sex , and height . Activity by accelerometer was not associated with bone gains . CONCLUSIONS Adiposity and TV viewing are related to less bone accrual in preschoolers
Several studies that used DXA or quantitative ultrasound suggested that objective ly measured SB was negatively associated with lower extremity bone outcomes , such as femoral neck bone mineral density .
The magnitude of this negative association was small and independent of moderate-to-vigorous physical activity .
In contrast to the lower extremities , there was insufficient evidence for an association of lumbar spine bone outcomes with objective ly measured SB .
In high- quality studies that used DXA , no association was observed between objective ly measured SB and total body bone outcomes .
In studies using question naires , none of these relationships were observed .
Sedentary  behaviour ( SB ) is increasing in Western societies and some studies suggest a deleterious effect of SB on bone .
The aim of this systematic review was to examine the association between  SB and bone health in children , adolescents and young adults .