A temporary decrease in mineral density in perinatal mouse long bones.

Fetal and postnatal bone development in humans is traditionally viewed as a process characterized by progressively increasing mineral density. Yet, a temporary decrease in mineral density has been described in the long bones of infants in the immediate postnatal period. The mechanism that underlies this phenomenon, as well as its causes and consequences, remain unclear. Using daily µCT scans of murine femora and tibiae during perinatal development, we show that a temporary decrease in tissue mineral density (TMD) is evident in mice. By monitoring spatial and temporal structural changes during normal growth and in a mouse strain in which osteoclasts are non-functional (Src-null), we show that endosteal bone resorption is the main cause for the perinatal decrease in TMD. Mechanical testing revealed that this temporary decrease is correlated with reduced stiffness of the bones. We also show, by administration of a progestational agent to pregnant mice, that the decrease in TMD is not the result of parturition itself. This study provides a comprehensive view of perinatal long bone development in mice, and describes the process as well as the consequences of density fluctuation during this period.

Osteocalcin is independently associated with body mass index in adolescent girls.

OBJECTIVE: Osteocalcin is a bone-related protein, recently found to correlate with body mass index (BMI), waist circumference, fat percentage and metabolic syndrome in adults. The aim of this study was to determine the relationship between osteocalcin and BMI in adolescence, a time of significant bone accrual, while considering possible confounders related to bone and body composition. METHODS: We analyzed data from 160 female adolescents (mean age 15.1 ± 0.7 years), which were divided into tertiles by osteocalcin levels. Across these three groups, we examined the differences in BMI with relation to age, total daily energy intake, calcium intake, physical activity (PA), total body bone mineral density, parathyroid hormone (PTH), 25(OH)-vitamin D, bone alkaline phosphatase and body fat percentage. RESULTS: Mean BMI values differed significantly between participants in the three osteocalcin tertiles, including after adjustment for age, PA, PTH, energy and calcium intakes. Post-hoc analysis revealed that girls in the highest osteocalcin tertile, had a significantly lower BMI than those in the two lower ones (19.3 ± 2.2 vs. 20.6 ± 3.0 and 20.7 ± 2.9 kg m(-2), respectively, P = 0.018). There was no significant difference in energy and calcium intakes, bone mineral density, 25(OH)-vitamin D levels and PTH between study groups. CONCLUSIONS: In female adolescents, BMI is inversely related to osteocalcin, even after consideration of several factors that may affect bone and fat mass. As bone mineral density, 25(OH)D and PTH did not differ between groups, it is possible that the relation between osteocalcin and BMI could be unrelated to bone tissue itself.

Influence of water drinking on resting energy expenditure in overweight children.

BACKGROUND: It was previously demonstrated that drinking water significantly elevates the resting energy expenditure (REE) in adults, and that low water intake is associated with obesity and lesser success in weight reduction. This study addressed the potential of water drinking to increase the REE in children, as an additional tool for weight management. OBJECTIVE: To examine the effect of drinking water on the REE of overweight children. DESIGN: A total of 21 overweight, otherwise-healthy children (age 9.9±1.4 years, 11 males) drank 10 ml kg(-1) cold water (4 °C). REE was measured before and after water ingestion, for 66 min. The main outcome measure was the change in mean REE from baseline values. RESULTS: Immediately after drinking water, there was a transient decrease in REE, from a baseline value of 3.32±1.15 kilojoule (kJ) per min to 2.56±0.66 kJ per min at minute 3 (P=0.005). A subsequent rise in REE was then observed, which was significantly higher than baseline after 24 min (3.89±0.78 kJ/min (P=0.021)), and at most time points thereafter. Maximal mean REE values were seen at 57 min after water drinking (4.16±1.43 kJ per min (P=0.004)), which were 25% higher than baseline. REE was significantly correlated with age, height, weight and fat-free mass; the correlations with maximal REE values after water drinking were stronger than with baseline REE values. CONCLUSIONS: This study demonstrated an increase of up to 25% in REE following the drinking of 10 ml kg(-1) of cold water in overweight children, lasting for over 40 min. Consuming the recommended daily amount of water for children could result in an energy expenditure equivalent to an additional weight loss of about 1.2 kg per year. These findings reinforce the concept of water-induced REE elevation shown in adults, suggesting that water drinking could assist overweight children in weight loss or maintenance, and may warrant emphasis in dietary guidelines against the obesity epidemic.

Diet and lifestyle in managing postmenopausal obesity.

The majority of adults are becoming increasingly overweight and one of the sub-populations in which this prevalence is growing most rapidly is postmenopausal women. It is as yet unclear whether the menopausal transition itself leads to weight gain, but it is known that the physiological withdrawal of estrogen brings about changes in fat distribution that increase the risk for the metabolic syndrome, diabetes and cardiovascular disease. The treatment of postmenopausal obesity is very simple logically, but incredibly difficult - eat less and exercise more. Recent studies suggest that being active and fit is more important than losing weight; hence, a major recommendation is to exercise regularly, for at least 30 min on at least 5 days of the week, while maintaining a healthy balanced diet. Unfortunately, there are no 'magic bullets' (drugs) that may provide long-term treatment, and all diets work irrespective of their composition as long as people comply to them. There is no substitute for a sensible lifestyle.