Weight Loss Through Calorie Restriction, But Not Exercise,
May Lead To Bone Loss
December 19, 2006
Most U.S. adults are either overweight or
obese . The primary treatment for these conditions
is lifestyle modification, including exercise and low-calorie
diets. However, decreasing body weight is associated with
decreased bone mineral density, which increases the risk for
osteoporosis (weakening of the bones) and hip fractures in
older men and women.
calorie-restriction also lost an average
of 2.2 percent of their bone density in the lower spine, 2.2
percent at the hip and 2.1 percent at the top end of the femur--all
high-risk fracture sites. There were no significant changes
in bone mineral density in the exercise or healthy lifestyle
groups. In both weight-loss groups, bone turnover--which occurs
when old bone is broken down--increased, as indicated by the
markers of bone turnover in the blood.
A common explanation given for the bone loss
induced by weight
loss is reduction in mechanical stress on the weight-bearing
skeleton (i.e., hip and spine).
"Accordingly, the preservation of bone
mineral density in the exercise group could be mediated through
exercise-induced bone loading." In addition, although
both weight-loss groups experienced an increase in bone turnover,
this was only detrimental to the calorie restriction group.
Muscles pulling on bones during exercise is thought to produce
strains in the skeleton that stimulate new bone production.
"Results are consistent with an osteoprotective
effect of exercise-induced mechanical strain on the skeleton
and consequent increase in bone turnover.
These findings have important implications
in designing an appropriate weight-loss therapy
program in middle-aged adults, particularly in the subset
of patients who may already be at increased risk for bone
fracture" .
Source from:
http://www.sciencedaily.com
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