L. Hyldstrup et al., BONE METABOLISM IN OBESITY - CHANGES RELATED TO SEVERE OVERWEIGHT ANDDIETARY WEIGHT-REDUCTION, Acta endocrinologica, 129(5), 1993, pp. 393-398
A non-invasive evaluation of bone metabolism was performed in 44 morbi
dly obese patients before and after a mean weight loss of 22.4 kg (ran
ge 7.9-4 3.4 kg) after 2 months and a further weight loss of 7.3 kg af
ter 8 months (0.8-20.0 kg). This weight reduction was obtained by a nu
tritionally adequate very-low-calorie diet. Before treatment the bone
mineral content of the distal forearm was increased compared to normal
s (51.9 U vs 43.7- U, p<0.001). Bone formation was evaluated by serum
alkaline phosphatase and serum osteocalcin. Serum alkaline phosphatase
was increased (187.8 U/l vs 147.4 U/l, p<0.001) while serum osteocalc
in was lower than in the controls (0.67 nmol/l vs 0.98 nmol/l, p<0.01)
. Bone resorption. as measured by the urinary hydroxyproline/creatinin
e ratio, was not increased in the obese patients (19.2 molar ratio x 1
0(-3) vs 16.7 molar ratio x 10(-3), NS). After 2 months, the bone mine
ral content had declined by 3.3%. Serum alkaline phosphatase remained
unchanged (187.8 U/l vs 186.9 U/l, NS) but serum osteocalcin demonstra
ted a significant rise (3.94 nmol/l vs 10.53 nmol/l, p<0.001), paralle
l to changes in the hydroxyproline/creatinine ratio (19.2 molar ratio
x 10(-3) vs 25.2 molar ratio x 10(-3). p<0.001). At 8 months, no furth
er change in the bone mineral content was seen. The hydroxyproline/cre
atinine ratio did still increase (from 25.8 molar ratio x 10(-3) to 30
.1 molar ratio x 10(-3). p<0.05). while serum alkaline phosphatase and
serum osteocalcin remained unchanged. In conclusion, the bone mineral
content is increased in morbid obesity. During weight loss obtained b
y a very-low-calorie diet supplying the recommended amounts of vitamin
D and minerals. bone resorption is increased rapidly and bone mass re
duced. Owing to linkage of bone remodelling processes. bone formation
increases with a longer observation period and the bone mineral conten
t is stabilized.