Moderate energy restriction increases bone resorption in obese postmenopausal women

Weight-bearing, aerobic exercise increases markers of bone formation during short-term weight loss in overweight and obese men and women

We investigated the impact of weight-bearing, aerobic exercise- and diet-induced weight loss on markers of bone turnover during a larger study of changes in metabolic fitness during short-term weight reduction using a repeated-measures, within-subject experimental design. Subjects (N = 19) underwent 6 weeks of energy restriction (reduced by approximately 3140 kJ/d) and aerobic exercise ( approximately 1675 kJ/d, walking or jogging at 60% maximum oxygen consumption) to induce a 5% reduction in body weight. Bone turnover markers and hormones were measured in serum collected at baseline and after 6 weeks of weight loss. Despite a 5% reduction in body weight at week 6, markers of bone formation, osteocalcin, and bone alkaline phosphatase, were significantly increased, and resorption markers, C-terminal cross-links of type I collagen and soluble receptor activator of nuclear factor kappaB ligand, were unchanged after 6 weeks of energy restriction and exercise. The concentration of leptin was significantly reduced after weight loss, but insulin-like growth factor I (IGF-I) and cortisol levels were unaffected. In conclusion, weight-bearing, aerobic exercise training may favorably affect the balance between bone resorption and formation during weight loss.

True fractional calcium absorption is decreased after Roux-en-Y gastric bypass surgery

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) is considered to be the gold standard alternative treatment for severe obesity. Weight loss after RYGB results primarily from decreased food intake. Inadequate calcium (Ca) intake and metabolic bone disease can occur after gastric bypass. To our knowledge, whether malabsorption of Ca contributes to an altered Ca metabolism in the RYGB patient has not been addressed previously.

RESEARCH METHODS AND PROCEDURES

We recruited 25 extremely obese women in order to study true fractional Ca absorption (TFCA) before and 6 months after RYGB surgery, using a dual stable isotope method ((42)Ca and (43)Ca) and test load of Ca (200 mg). Hormones regulating Ca absorption and markers of bone turnover were also measured.

RESULTS

In 21 women (BMI 52.7 +/- 8.3 kg/m(2), age 43.9 +/- 10.4 years) who successfully completed the study, TFCA decreased from 0.36 +/- 0.08 to 0.24 +/- 0.09 (p < 0.001) after RYGB. Bone turnover markers increased significantly (p < 0.01). TFCA correlated with estradiol levels (r = 0.512, p < 0.02) and tended to correlate with 1,25 (OH)(2)D (r = 0.427, p < 0.06) at final measurement. Stepwise linear regression indicated that estradiol explained 62% of the variance for TFCA at 6 months post-surgery (p < 0.01).

DISCUSSION

TFCA decreases (0.12 +/- 0.08) after RYGB surgery but remains within normal range. Although only some patients were estimated to have low Ca absorption after surgery, all of the patients showed a dramatic increase in markers of bone resorption. The alteration in Ca metabolism after RYGB-induced weight loss appears to be regulated primarily by estradiol levels and might ultimately affect bone mass.

Simulated change in body fatness affects Hologic QDR 4500A whole body and central DXA bone measures

Changes in body fatness may impact the accuracy of dual energy X-ray absorptiometry (DXA) measures of bone mineral content (BMC) and bone mineral density (BMD). The aim of this study was to determine if DXA can accurately assess BMC and BMD with changes in exogenous fat (lard) placed to simulate weight change. Whole body (WB), lumbar spine (LS), and proximal femur (PF) DXA scans (Hologic QDR 4500A) were performed on 30 elderly (52-83 yr) and 60 young (18-40 yr) individuals (i.e., 45 females and 45 males) of varying body mass index (mean+/-standard deviation: 26.1+/-4.9 kg/m2). When scans were repeated with lard packets (2.54 cm thick, 25.4x17.8 cm, 1 kg), WB BMD decreased 1.1% and 1.6% after chest and thigh packet placement, respectively (p=0.001), PF BMD increased 0.7% (p=0.02) and LS BMD decreased 1.6% (p=0.001) primarily due to a 2.2% reduction in LS BMC (p<0.001). Initial LS BMC and trunk mass were related to error in LS BMC measures due to lard-loading (r=0.64 and 0.45, respectively, p<0.001). We conclude that on average simulated weight change minimally impacts PF bone measures and moderately impacts WB and LS bone measures; however, individual variability in measurement error was noteworthy and may be impacted by body thickness.

Bone Density in Elite Judoists and Effects of Weight Cycling on Bone Metabolic Balance

PURPOSE

Weight cycling has been shown to exert negative effects on bone metabolism and bone mass, whereas weight-bearing activity is positively associated with bone mineral density (BMD). Bone health in judoists and effects of weight cycling on bone metabolism have not previously been investigated. To examine potential disrupter and stimulators of bone integrity, this study analyzed bone parameters at baseline and the effects of the first weight cycle of the season on bone metabolic status in 48 male and female elite judoists.

METHODS

Body composition and lumbar, femoral, and total body BMD were evaluated by dual-energy x-ray absorptiometry. Cortisol, osteocalcin, C-terminal telopeptide of type I collagen (CTx), and bone uncoupling index (UI) were measured in judoists at normal body weight, after weight reduction, and after regaining weight. As a comparison, a control group of moderately active students was included at baseline. Training, menstrual status, and calcium intake were assessed by questionnaires.

RESULTS

EUweighted judoists displayed high BMD and an increased rate of bone formation. Precompetitive weight loss averaged 4 +/- 0.3% of body weight and induced an acute rise in cortisol (81%, P < 0.05) and CTx (33%, P < 0.0001), with a metabolic imbalance in favor of bone resorption. A 4 +/- 0.5% weight regain restored a positive UI in favor of bone formation. Metabolic responses were not dependent on gender. BMD was unaltered by weight cycling.

CONCLUSIONS

Increased bone formation rate pertaining to judo athletes lent protection from alterations in bone metabolic balance associated with weight cycling. This observation suggests that powerful osteogenic stimuli provided by judo's unique biomechanical environment may help prevent bone loss associated with weight loss.

Relationships between serum leptin and bone markers during stable weight, weight reduction and weight regain in male and female judoists

OBJECTIVE

Despite a preliminary understanding of leptin-skeletal interactions, data in humans are inconsistent and the exact roles of leptin on bone metabolism have not yet been defined. The aim of this study was to examine the possible role of leptin in the regulation of bone metabolism in healthy, physically trained adults.

METHODS AND DESIGN

Body composition and bone mass (dual-energy X-ray absorptiometry), anthropometry, serum leptin, insulin, cortisol, osteocalcin, C-terminal telopeptide of type I collagen (CTx) and total plasma proteins were measured in judoists at normal body weight, after weight reduction and after weight regain. Physical training, weight cycling history, menstrual status and nutritional intake using a 7-day food record were assessed.

RESULTS

Precompetitive weight loss averaged 4 +/- 0.3% of bodyweight and resulted in a significant decrease in leptin levels of 64% (P < 0.001) and of 31% for insulin (P < 0.0001). CTx and cortisol concentrations rose by 33% (P < 0.0001) and 81% (P < 0.05) respectively. Osteocalcin and total plasma protein remained unaffected by weight loss. A 4 +/- 0.5% weight regain induced a 276% increase in leptin levels (P < 0.001) and an 18% increase in insulin (P < 0.001). CTx and cortisol decreased by 23% (P < 0.0001) and 27% (P < 0.05) respectively. Changes in leptin were significantly correlated with changes in bone resorption marker in response to both weight loss (r = 0.56, P < 0.01) and regain (r = 0.44, P < 0.05).

CONCLUSIONS

These findings suggest that leptin is involved in the regulation of bone metabolism in healthy adults and might play a potential role in the prevention of osteoporosis.

Immobilization decreases duodenal calcium absorption through a 1,25-dihydroxyvitamin D-dependent pathway

Immobilization induces significant and progressive bone loss, with an increase in urinary excretion and a decrease in intestinal absorption of calcium. These actions lead to negative calcium balance and the development of disuse osteoporosis. The aims of this study were to evaluate the molecular mechanisms of decreased intestinal calcium absorption and to determine the effect of dietary 1,25-dihydroxyvitamin D [1,25(OH)2D] and a high-calcium diet on bone loss due to immobilization. The immobilized rat model was developed in the Bollman cage III to induce systemic disuse osteoporosis in the animals. There was a significant decrease in lumbar bone mineral density (BMD) and intestinal calcium absorption in the immobilized group compared with the controls. Serum 25-hydroxyvitamin D concentration did not change, but 1,25(OH)2D concentration decreased significantly. The mRNA levels of renal 25-hydoxyvitamin D 24-hydroxylase (24OHase) increased, whereas those of renal 25-hydroxyvitamin D 1-alpha hydroxylase (1alpha-hydroxylase), duodenal transient receptor potential cation channel, subfamily V, member 6 (TRPV6), TRPV5, and calbindin-D9k were all decreased. A high-calcium diet did not prevent the reduction in lumbar BMD or affect the mRNA expression of proteins related to calcium transport. Dietary administration of 1,25(OH)2D increased the intestinal calcium absorption that had been downregulated by immobilization. TRPV6, TRPV5, and calbindin-D9k mRNA levels were also upregulated, resulting in prevention of the reduction in lumbar BMD. Therefore, it is concluded that dietary 1,25(OH)2D prevented decreases in intestinal calcium absorption and simultaneously prevented bone loss in immobilized rats. However, it remains unclear that calcium absorption and expression of calcium transport proteins are essential for the regulation of lumbar BMD.

Genetic determination and correlation of body mass index and bone mineral density at the spine and hip in Chinese Han ethnicity

The purpose of the present study was to evaluate the magnitude of genetic determination of spine and hip bone mineral density (BMD) and body mass index (BMI), and to explore the genetic, environmental, and phenotypic correlations among the above phenotypes in Chinese Han ethnicity. The sample was composed of at least 217 complete nuclear families in Chinese Han ethnicity. BMD at the spine and hip was measured using a dual-energy X-ray absorptiometry scanner. The heritability (h2) of BMI and BMD at the spine and hip, the genetic correlation (rhoG) and environmental correlation (rhoE) among the three phenotypes were evaluated via variance analysis, with age, sex, and age-by-sex interaction as covariates. The phenotypic correlation (rhoP) and the bivariate heritability rhoG2 were also calculated. The heritability for BMD and BMI was approximately 0.70 and approximately 0.50, respectively (p<0.0001). The common environment shared by household members (household effect) is significant for BMI variation (p=0.0004). Significant genetic, environmental, and phenotypic correlation was observed. The rhoG2 values were 0.13 for BMI/spine BMD, 0.18 for BMI/hip BMD, and 0.58 for the spine BMD/hip BMD. While BMD at the spine and hip have significant genetic determination, BMI is more likely to be affected by environmental factors than BMD. In addition, BMD at the spine and hip shares more genetic effect (pleiotropy) than BMI and BMD do in Chinese Han ethnicity, though the effects are significant for both.

The effect of a low-carbohydrate diet on bone turnover

INTRODUCTION

Low-carbohydrate diets have become popular as weight loss techniques. These diets are high in protein, saturated fats, and omega-6 fatty acids. They also lead to a ketogenic state. These factors could lead to increased bone turnover. This study was designed to see whether a low-carbohydrate diet would lead to increased bone turnover in humans.

METHODS

Thirty patients (15 study subjects and 15 controls) were recruited for this 3-month study. The 15 patients on the diet were instructed to consume less than 20 g of carbohydrates per day for the 1st month and then less than 40 g per day for months 2 and 3. Control subjects had no restrictions on their diet. The primary end point was urinary N-telopeptide (UNTx) at 3 months. Secondary end points included UNTx at 1 month, bone-specific alkaline phosphatase (BSAP) at 1 month, bone turnover ratio (BSAP/UNTx) at 1 month, and weight loss.

RESULTS

The mean UNTx in the study subjects increased by 1.6 [95% confidence interval (CI) +/-22.8] compared with an increase of 1.9 (95% CI +/-17.6) in the controls at 3 months (p=0.86). The mean UNTx decreased by 2.2 (95% CI +/-27.2) and 3.1 (95% CI +/-17.6) at 1 month in the dieters and controls, respectively (p=0.36). The mean BSAP decreased by 0.53 (95% CI +/-2.96) in the dieters and increased by 0.34 (95% CI +/-2.92) in the controls at 1 month (p=0.27). The bone turnover ratio increased by 0.08 (95% CI +/-0.81) in the dieters and by 0.05 (95% CI +/- 0.27) in the controls at 1 month (p=0.78). The dieters lost 6.39 kg versus 1.05 kg for the controls at 3 months (p=0.0008).

CONCLUSIONS

Although the patients on the low-carbohydrate diet did lose significantly more weight than the controls did, the diet did not increase bone turnover markers compared with controls at any time point. Further, there was no significant change in the bone turnover ratio compared with controls.

Does high-intensity resistance training maintain bone mass during moderate weight loss in older overweight adults with type 2 diabetes?

The aim was to investigate whether the addition of supervised high intensity progressive resistance training to a moderate weight loss program (RT+WLoss) could maintain bone mineral density (BMD) and lean mass compared to moderate weight loss (WLoss) alone in older overweight adults with type 2 diabetes. We also investigated whether any benefits derived from a supervised RT program could be sustained through an additional home-based program. This was a 12-month trial in which 36 sedentary, overweight adults aged 60 to 80 years with type 2 diabetes were randomized to either a supervised gymnasium-based RT+WLoss or WLoss program for 6 months (phase 1). Thereafter, all participants completed an additional 6-month home-based training without further dietary modification (phase 2). Total body and regional BMD and bone mineral content (BMC), fat mass (FM) and lean mass (LM) were assessed by DXA every 6 months. Diet, muscle strength (1-RM) and serum total testosterone, estradiol, SHBG, insulin and IGF-1 were measured every 3 months. No between group differences were detected for changes in any of the hormonal parameters at any measurement point. In phase 1, after 6 months of gymnasium-based training, weight and FM decreased similarly in both groups (P<0.01), but LM tended to increase in the RT+WLoss (n=16) relative to the WLoss (n=13) group [net difference (95% CI), 1.8% (0.2, 3.5), P<0.05]. Total body BMD and BMC remained unchanged in the RT+WLoss group, but decreased by 0.9 and 1.5%, respectively, in the WLoss group (interaction, P<0.05). Similar, though non-significant, changes were detected at the femoral neck and lumbar spine (L2-L4). In phase 2, after a further 6 months of home-based training, weight and FM increased significantly in both the RT+WLoss (n=14) and WLoss (n=12) group, but there were no significant changes in LM or total body or regional BMD or BMC in either group from 6 to 12 months. These results indicate that in older, overweight adults with type 2 diabetes, dietary modification should be combined with progressive resistance training to optimize the effects on body composition without having a negative effect on bone health.

Obesity in older adults: technical review and position statement of the American Society for Nutrition and NAASO, The Obesity Society

Obesity causes serious medical complications and impairs quality of life. Moreover, in older persons, obesity can exacerbate the age-related decline in physical function and lead to frailty. However, appropriate treatment for obesity in older persons is controversial because of the reduction in relative health risks associated with increasing body mass index and the concern that weight loss could have potential harmful effects in the older population. This joint position statement from the American Society for Nutrition and the NAASO, The Obesity Society reviews the clinical issues related to obesity in older persons and provides health professionals with appropriate weight-management guidelines for obese older patients. The current data show that weight-loss therapy improves physical function, quality of life, and the medical complications associated with obesity in older persons. Therefore, weight-loss therapy that minimizes muscle and bone losses is recommended for older persons who are obese and who have functional impairments or medical complications that can benefit from weight loss.

Parathyroid hormone is associated with decreased fat mass in young healthy women

OBJECTIVE

To investigate the relationship of parathyroid hormone (PTH) with dietary calcium and changes in body composition.

DESIGN

Cross-sectional and 1-year longitudinal trial.

SUBJECTS

Normal-weight young women (age: 18-31), 155 subjects analyzed at baseline, and data for 41 subjects analyzed prospectively between baseline and 12 months.

MEASUREMENTS

Levels of fasting serum calcium and PTH, intakes of calcium (3-day diet records), and total body weight and body composition (dual energy X-ray absorptiometry).

RESULTS

Baseline dietary calcium, regardless of whether unadjusted or adjusted for energy intake, did not predict baseline levels of fasting serum PTH. Change in dietary calcium also did not predict change in serum PTH. However, log PTH was significantly correlated with body fat mass (R = 0.27), but not lean mass at baseline (n = 155), independent of serum calcium (corrected R = 0.25). Further, 12-month changes (n = 41) in log PTH positively predicted the 12-month change in body weight (R = 0.32) and body fat (R = 0.32), but not lean mass even when controlled for age or change in serum calcium.

CONCLUSION

Fasting serum PTH was associated with increased fat mass, in both cross-sectional and prospective analysis. Thus, serum PTH may play a role in the regulation of body fat mass in young women.

Diabetes and bone loss at the hip in older black and white adults

Type 2 diabetes may be associated with elevated fracture risk, but the impact on bone loss is unknown. Analysis of 4-year change in hip BMD data from a cohort of white and black well-functioning men and women 70-79 years of age found that white women with diabetes had more rapid bone loss at the femoral neck than those with normal glucose metabolism.

INTRODUCTION

Type 2 diabetes may be associated with elevated fracture risk in older adults. Although type 2 diabetes is not associated with lower BMD, older diabetic adults have a higher prevalence of other risk factors for fracture, including more frequent falls, functional limitations, and diabetic complications. With this burden of risk factors, loss of BMD could place older adults with diabetes at higher risk of sustaining a fracture.

MATERIALS AND METHODS

To determine if bone loss is increased with type 2 diabetes, we analyzed data from the Health, Aging, and Body Composition Study of white and black well-functioning men and women 70-79 years of age. Hip BMD was measured at baseline and 4 years later in 480 (23%) participants with diabetes, 439 with impaired glucose metabolism, and 1172 with normal glucose homeostasis (NG).

RESULTS

Those with diabetes had higher baseline hip BMD and weight, but among white women, had more weight loss over 4 years. White women with diabetes lost more femoral neck and total hip BMD than those with NG in age-adjusted models. After multivariable adjustment, diabetes was associated with greater loss of femoral neck BMD (-0.32%/year; 95% CI: -0.61, -0.02) but not total hip BMD. In men and black women, change in hip BMD was similar for participants with diabetes and NG.

CONCLUSIONS

Despite having higher baseline BMD, diabetic white women, but not men or black women, had more rapid bone loss at the femoral neck than those with NG. This increased bone loss may contribute to the higher fracture risk observed in older diabetic women.

Overweight postmenopausal women lose bone with moderate weight reduction and 1 g/day calcium intake

Overweight postmenopausal women may be more susceptible to bone loss with weight reduction than previously studied obese women. The influence of energy restriction and Ca intake on BMD was assessed in 66 individuals. Weight reduction resulted in bone loss at several sites in women consuming 1 g Ca/day and was mitigated with higher calcium intake at 1.7 g/day.

INTRODUCTION

Bone loss is associated with weight loss in obese postmenopausal women and can be prevented with calcium (Ca) supplementation. However, because bone loss caused by weight loss may be greater in overweight than obese women, it is not clear whether Ca supplementation is also beneficial in overweight women.

MATERIALS AND METHODS

We assessed the influence of caloric restriction at two levels of Ca intake on BMD and BMC in 66 overweight postmenopausal women (age, 61 +/- 6 years; body mass index, 27.0 +/- 1.8 kg/m2). Subjects completed either a 6-month energy-restricted diet (WL, n = 47) and lost 9.3 +/- 3.9 % weight or maintained weight (WM; 1 g Ca/day, n = 19). Participants in the WL group were randomly assigned to either normal (1 g/day; WL NL-Ca) or high (1.7 g/day; WL Hi-Ca) Ca intake. Regional BMD and BMC were measured at baseline and after 6 months.

RESULTS

During normal Ca intake, trochanter BMD and BMC and total spine BMD were decreased more in WL than WM women (p < 0.05). The WL NL-Ca group lost more trochanter BMD (-4.2 +/- 4.1%) and BMC (-4.8 +/- 7.1%) than the WL Hi-Ca group (-1.4 +/- 5.6% and -1.1 +/- 8.1%, respectively; p < 0.05). There were no significant changes in BMD or BMC at the femoral neck in any group. Weight loss correlated with trochanter BMD loss (r = 0.687, p < 0.001) in the WL NL-Ca group.

CONCLUSION

Despite an intake of 1 g Ca/day, bone loss occurred at some sites because of weight loss. Calcium intake of 1.7 g/day will minimize bone loss during weight loss in postmenopausal overweight women.

Caloric restriction and calcium's effect on bone metabolism and body composition in overweight and obese premenopausal women

Obesity results in numerous preventable deaths and comorbidities. Unfortunately, a reduction of body weight has been correlated with a reduction in bone mass, the reasons for which have not been fully elucidated. The importance of maximizing peak bone mass during premenopausal years is well known. Most studies demonstrate a positive relationship between calcium intake and bone mass. However, during caloric restriction, which is commonly used for weight loss, calcium intake has shown mixed results. Calcium from dairy sources has received additional attention, beyond its importance to bone, for its role in regulating body weight and composition. Dairy foods are perceived as high fat, and therefore, are generally minimized or avoided during caloric restriction. The current calcium intake for premenopausal women is significantly below recommendations, and even if met during caloric restriction, may not be adequate. This review underscores the need for maintaining at least adequate intake levels of calcium, if not more, during weight loss regimens to minimize potential long-term detrimental effects on bone metabolism.

Estrogen prevents the reduction in fractional calcium absorption due to energy restriction in mature rats

Weight reduction is a risk factor for bone loss. We previously showed that energy restriction is associated with a decrease in calcium (Ca) absorption and decreased estrogenic activity (EA). We hypothesized that this hypoestrogenic status may be the cause of the decrease in Ca absorption and that estrogen replacement during energy restriction would prevent it. Six-month-old rats were ovariectomized and implanted subcutaneously with 17beta-estradiol (E(2)) pellets to maintain levels within the physiological range. After 3 wk, rats ate ad libitum [control (CTL) group, n = 12] or were 40% energy restricted (EnR group, n = 12) for 10 wk. At the end of this study, rats were divided into 2 groups according to their uterine weight: those with higher EA and those with lower EA. Whereas CTL rats gained approximately 46% weight from baseline, EnR rats maintained their weight throughout the study. Energy restriction was associated with lower Ca absorption (5-d measurement, (45)Ca radioisotope) and Ca balance in lower EA but not higher EA rats. Similarly, Ca absorption was correlated with both serum E(2) (r = 0.68, P < 0.05) and body weight (r = 0.72, P < 0.05) in rats with lower EA but not in those with higher EA. Finally, 24-h corticosterone excretion was higher in EnR than in CTL rats, a response that was blunted in the higher EA rats. Our findings suggest that decreases in estrogen and hyperadrenocorticism with energy restriction play an important role in the regulation of Ca absorption and balance.

Body mass index (BMI) and parameters of bone formation and resorption in postmenopausal women

OBJECTIVES

Aim of this study was to evaluate increased body mass index (BMI) as an anthropometric factor, predisposing to lower rates of bone turnover or changes in bone balance after menopause.

MATERIAL AND METHODS

For this purpose, we calculated BMI, and measured spinal (BMD(SP)) and femoral bone mineral density (BMD(FN)) and biochemical markers of bone formation (serum osteocalcin (S-OC), serum procollagen type I C propeptide (S-PICP), serum bone-specific alkaline phosphatase (S-B-ALP)) and resorption (urine N- and C-terminal cross-linking telopeptide of type I collagen (U-NTX-I and U-CTX-I), pyridinoline (U-PYD) and deoxypyridinoline (U-DPD)) in 130 healthy postmenopausal women, aged 46-85 years. Bone balance indices were calculated by subtracting z-scores of resorption markers from z-scores of formation markers, to evaluate bone balance.

RESULTS

S-PICP ( r = -0.297, P = 0.002), S-OC ( r = -0.173, P = 0.05) and bone balance indices (zPICP-zDPD) and (zPICP-zPYD) were negatively correlated with BMI (r = -0.25, P = 0.01 and r = -0.25, P = 0.01 and r = -0.21, P = 0.037) and with BMD(SP) (r = -0.196, P = 0.032 and r = -0.275 and P = 0.022). Women were grouped according to their BMI, in normals (BMI < 25 kg/m2), overweight (BMI = 25-30 kg/m2, and obese (BMI > 30 kg/m2). Overweight and obese women had approximately 30% lower levels of S-PICP compared to normals (68.11 +/- 24.85 and 66.41 ng/ml versus 97.47 +/- 23.36 ng/ml, respectively; P = 0.0001). zPICP-zDPD, zPICP-zCTX-I and zPICP-zPYD were significantly declined in obese women compared to normals (P = 0.0072, 0.02 and 0.0028).

CONCLUSIONS

We conclude that in postmenopausal women, BMI is inversely associated with levels of collagen I formation marker, serum PICP. In obesity formation of collagen I was reduced, in favor of degradation, but since this finding is not followed by simultaneous decrease in bone mineral density, it seems that increased body weight may have different effects on mature estrogen-deficient bone and extraskeletal tissues containing collagen I.

Changes in bone mineral content after surgical treatment of morbid obesity

Weight loss reduces bone mass and increases the risk of osteoporosis. This study was undertaken to assess changes of bone metabolism following Roux-en-Y gastric bypass (RYGB) and adjustable silicone gastric banding (ASGB) as compared to nonoperated controls of morbidly obese subjects. Fourteen female and 5 male patients with a mean (+/-SEM) age of 44.3 +/- 1.8 years participated in the 24-month prospective study. Nine patients underwent ASGB, 4 patients RYGB operation, and 6 patients were included in the control group. Bone metabolism was assessed by determination of serum parathyroid hormone (PTH), osteocalcin, urinary deoxypyridinoline, and dual energy x-ray absorptiometry (DXA) before, and 6, 12, and 24 months after intervention. The body mass index (BMI) decreased from 41.0 +/- 1.1 to 34.0 +/- 1.4 kg/m2 in the ASGB group (P = .001), from 42.7 +/- 2.2 to 30.5 +/- 2.2 kg/m2 in the RYGB group (P = .006), and remained unchanged in the control group (from 41.2 +/- 1.2 to 41.4 +/- 1.4 kg/m2) after 24 months. Bone mineral content (BMC) showed no significant change in the ASGB group (from 3,079 +/- 140 to 3,064 +/- 129 g) and in the control group (from 2,945 +/- 130 to 2,940 +/- 111 g), whereas it decreased from 2,968 +/- 111 to 2,621 +/- 139 g in the RYGB group (P = .005). The loss in BMC was accompanied by significant increases in urinary deoxypyridinoline (P < .05) and in serum osteocalcin (P < .01) after RYGB, suggesting both, increased bone resorption and increased bone formation. The authors were aware of the fact that the study groups were small and conclusions need to be regarded as preliminary. However, the RYGB operation resulted in enhanced weight loss and significant net loss of bone mass in comparison to ASGB and obese control subjects. Patients losing large amounts of body weight should be monitored regularly regarding prevention of osteoporosis.

Weight loss and calcium intake influence calcium absorption in overweight postmenopausal women

BACKGROUND

Weight loss (WL) reduces bone mass and increases fracture risk. Mechanisms regulating calcium metabolism during WL are unclear.

OBJECTIVE

The objective was to assess the effect of 6 wk of WL at 2 different amounts of calcium intake [normal (NlCa): 1 g/d; high (HiCa): 1.8 g/d] on true fractional calcium absorption (TFCA), bone turnover, and bone-regulating hormones in overweight postmenopausal women.

DESIGN

Seventy-three women (body mass index, 26.9 +/- 1.9 kg/m(2)) were recruited either to consume a moderately energy-restricted diet (WL group) or to maintain their body weight [weight-maintenance (WM) group] and were randomly assigned to either the HiCa or the NlCa group in a double-blind manner. Subjects underwent weekly diet counseling, and measurements were taken at baseline and after 6 wk.

RESULTS

Fifty-seven women completed the study and had a baseline TFCA of 24.9 +/- 7.4%. Energy restriction significantly decreased the total calcium absorbed (P < 0.05) in the WL group (n = 32) compared with the WM group (n = 25; analysis of covariance). Regression analysis showed that a greater rate of weight loss suppressed TFCA and the total calcium absorbed (P < 0.05) in the HiCa group. The women in the NlCa WL group absorbed inadequate amounts of calcium (195 +/- 49 mg/d), whereas the women in the HiCa WL group absorbed adequate amounts (348 +/- 118 mg/d). Parathyroid hormone explained 22% of the variance in calcium absorbed in the NlCa group only.

CONCLUSIONS

We suggest that WL is associated with elevated calcium requirements that, if not met, could activate the calcium-parathyroid hormone axis to absorb more calcium. Normal intakes of calcium during energy restriction result in inadequate total calcium absorption and could ultimately compromise calcium balance and bone mass.

Low bone mass in premenopausal chronic dieting obese women

BACKGROUND

Obese premenopausal women are thought to be at low risk for osteoporosis due to increased body weight and effects of estrogen on weight-bearing bone.

OBJECTIVE

To examine the effect of restrained eating on obese women, we examined bone mineral density (BMD) and content (BMC) of the spine and femur in obese women who were restrained eaters, with emphasis on the relationship between BMC and determinants of bone mass, and current eating behaviors, dietary intake, physical activity, and indices of calcium regulation, bone metabolism, stress and inflammation.

DESIGN

A total of 78 obese, Caucasian, female, restrained eaters, ages 30-45 y, were enrolled in a weight lose program. Height, weight, bone turnover markers, serum parathyroid hormone (PTH), cortisol, c-reactive protein (CRP), dietary intake, eating behaviors, physical activity, and BMD and BMC were measured.

SETTING

This study was conducted at the University of California, in Davis, CA, USA.

RESULTS

In all, 31% of women had osteopenia or osteoporosis (OSTEO). In the OSTEO group, 87.5% of women had osteoporosis or osteopenia of the lumbar spine and 12.5% of the women had osteoporosis or osteopenia in femur. A significant positive correlation between BMC and energy expenditure (r=0.256), and a significant negative correlation between BMC and number of times on a weight loss diet (r=-0.250) and cognitive restraint (r=-0.239) were observed. No significant differences were observed between OSTEO women and nonosteoporotic women for current eating behaviors, dietary intake, physical activity habits, bone turnover, calcium regulation, stress, or inflammation.

CONCLUSIONS

Obese restrained eaters are at risk for low bone mass. Prior dieting may be responsible. Chronic dieters should be encouraged to decrease their dietary restraint, develop healthy eating habits and increase physical activity.

A high dairy protein, high-calcium diet minimizes bone turnover in overweight adults during weight loss

Weight loss induces bone resorption and this can be attenuated by calcium supplementation. Protein-rich diets were recently associated with favorable effects on bone density, although this remains controversial. We hypothesized that a diet high in calcium and protein would minimize bone resorption during weight loss compared with a lower calcium, protein-rich diet. The effects of dietary calcium in high protein diets on calcium excretion and bone metabolism were examined in overweight adults (n = 50, BMI 33.4 +/- 2.1 kg/m(2)) during 12 wk of energy restriction followed by 4 wk of energy balance. Subjects were randomly assigned to isoenergetic diets (5.5 MJ/d, 34% energy from protein, 41% carbohydrate, 24% fat) high in either dairy protein (DP, 2400 mg Ca/d) or mixed protein sources (MP, 500 mg Ca/d). During energy restriction, weight loss was 10% (-9.7 +/- 3.8 kg, P < 0.01), and 24-h urinary calcium excretion decreased independently of diet (-1.09 +/- 0.23 mmol/d, P < 0.01). By wk 16, the MP diet group had a 40% greater increase in deoxypyridinoline (bone resorption marker) than the DP diet group (P = 0.008). Osteocalcin (bone formation marker) increased from wk 0 to 16 in only the MP diet group [+2.16 +/- 0.63 micro g/L (+0.63 +/- 0.11nmol/L), P = 0.001]. In conclusion, weight loss was associated with increased bone resorption, yet the DP diet had a modest advantage over the MP diet by minimizing overall turnover. Combined with reduced urinary calcium excretion, this suggests that a high-protein, calcium-replete diet may protect against bone loss during weight reduction.

Calcium in Women: Healthy Bones and Much More

Osteoporosis is one of the leading health problems of women today, and the expectation is that more than 41 million women worldwide will be affected within the next 20 years if current trends are not reversed. Prevention of osteoporosis must be a focus for nurses, rather than merely the treatment of the problem. The majority of bone mass is developed during the adolescent and young adulthood years, with nearly 90% of skeletal mass accumulated by age 18. Current research has demonstrated that young women's intake of calcium is significantly below the recommended dietary intake. This article reviews the role and functions of calcium, how it is transported, and factors that may significantly increase or impair the absorption of this macronutrient. Strategies are described that will assist nurses in assessing the patient's diet and making appropriate recommendations regarding the intake of calcium and other micronutrients. A more in-depth and thorough understanding of this important mineral will enable nurses to strengthen their knowledge and confidence in helping patients and themselves change the focus from treating the disease to the improvement and maintenance of healthy bones and the prevention of other health conditions in women.

Discordant effect of body mass index on bone mineral density and speed of sound

BACKGROUND

Increased BMI may affect the determination of bone mineral density (BMD) by dual X-ray absorptiometry (DXA) and speed of sound (SOS) measured across bones. Preliminary data suggest that axial SOS is less affected by soft tissue. The purpose of this study is to evaluate the effect of body mass index (BMI) on BMD and SOS measured along bones.

METHODS

We compared axial BMD determined by DXA with SOS along the phalanx, radius and tibia in 22 overweight (BMI > 27 kg/m2), and 11 lean (BMI = 21 kg/m2) postmenopausal women. Serum bone specific alkaline phosphatase and urinary deoxypyridinoline excretion determined bone turnover.

RESULTS

Mean femoral neck--but not lumbar spine BMD was higher in the overweight--as compared with the lean group (0.70 +/- 0.82, -0.99 +/- 0.52, P < 0.00001). Femoral neck BMD in the overweight--but not in the lean group highly correlated with BMI (R = 0.68. P < 0.0001). Mean SOS at all measurement sites was similar in both groups and did not correlate with BMI. Bone turnover was similar in the two study groups.

CONCLUSIONS

The high BMI of postmenopausal women may result in spuriously high BMD. SOS measured along bones may be a more appropriate means for evaluating bones of overweight women.

The menopause and obesity

In summary, menopause tends to be associated with an increased risk of obesity and a shift to an abdominal fat distribution with associated increase in health risks. Changes in body composition at menopause may be caused by the decrease in circulating estrogen, and, for fat distribution shifts, the relative increase in the androgen-estrogen ratio is likely to be important. Clinicians need to be aware of the likelihood of weight gain during the perimenopausal and postmenopausal years because behavioral strategies for weight loss can be effectively used in this population. Weight loss or prevention of weight gain is likely to have significant health benefits for older women.

Weight control and the management of obesity after menopause: the role of physical activity

BACKGROUND

Postmenopausal women have an increased tendency for gaining weight. The declines of endogenous estrogen, together with physical inactivity, are probably the major causes of this phenomenon. Postmenopausal overweight and obesity leads to increased rates of hypertension, diabetes mellitus, coronary artery disease, and all cause mortality. Additional consequences may include hormone-dependent cancer, gallstones, nephrolithiasis, and osteoarthritis. Weight loss can reverse many of these complications, reduce the number and dosages of medications used, and improve longevity. This difficult task requires lifestyle modification.

OBJECTIVES

To review the current information about the effects of physical activity on postmenopausal weight gain and its consequences and to provide basic strategies to treat obesity during the menopause transition.

METHODS

A Medline search together with a manual search of selected articles.

CONCLUSION

Several options for weight loss are available, yet lifestyle modification is essential in managing postmenopausal obesity and overweight. While this demands dietary and behavioral changes, a major element of this modification is regular physical activity, which reduces obesity-related morbidity and mortality. The amendment to a healthier lifestyle is achievable at the postmenopausal years. All medical personnel should advocate against overweight and obesity and provide tools for their management.

Relationships among body mass, its components, and bone

Body weight impacts on both bone turnover and bone density, and is therefore an important risk factor for vertebral and hip fractures, ranking in importance alongside that of age. The effect of body weight is probably contributed to by both fat mass and lean mass, although in postmenopausal women fat mass has been more consistently demonstrated to be important. A number of mechanisms for the fat-bone relationship exist and include the effect of soft tissue mass on skeletal loading, the association of fat mass with the secretion of bone-active hormones from the pancreatic beta cell (including insulin, amylin, and preptin), and the secretion of bone-active hormones (e.g., estrogens and leptin) from the adipocyte. These factors alone probably do not fully explain the observed clinical associations, and further study of the actions on bone of novel hormones related to nutrition is an important area of further research. An understanding of this aspect of bone biology may open the way for new treatments of osteoporosis. More immediately, the role of weight maintenance in the prevention of osteoporosis is an important public health message that needs to be more widely appreciated.

Nutrition and molecular markers of bone remodelling

PURPOSE OF REVIEW

Molecular markers of bone remodelling are noninvasive and comparatively inexpensive tools to evaluate the two major processes of bone renewal: bone formation and bone resorption. Over the past 10 years, research has generated a number of novel and specific bone markers that enable us to investigate those processes even more closely.

RECENT FINDINGS

It has been known for some time that nutritional and lifestyle factors are of great importance in the development and maintenance of normal bone mass and remodelling. Recent studies suggest that hypovitaminosis D is frequent in children and adolescent persons, and may affect their bone health. Clearly, chronic eating disorders such as anorexia nervosa are associated with high rates of bone resorption and bone loss, and increased fracture risk. In obese patients weight loss is associated with changes in both bone mineral density and bone remodelling, although the pathogenesis of these changes is ill defined.

SUMMARY

Nutritional and lifestyle factors influence bone mass and remodelling. Malnutrition, vitamin D deficiency, chronic and acute eating disorders, and diet-induced weight loss often induce high rates of bone resorption and bone loss.

Energy restriction reduces fractional calcium absorption in mature obese and lean rats

Weight loss is associated with bone loss and the risk may be greater in lean than heavier individuals, but the mechanisms involved remain unclear. We hypothesized that energy restriction (EnR) would decrease true fractional Ca absorption (TFCA) and be mediated by Ca-regulating hormones, but differently in obese and lean rats. Rats were fed a high fat (47% energy) or low fat (16% energy) diet for 4 mo. At 6 mo of age, the resulting lean [284 +/- 28g (mean +/- SD, n = 18)] and obese (319 +/- 34g, n = 20) groups (P < 0.005) were divided into controls (CTL, ad libitum) and energy-restricted (40% restriction) groups. At baseline, bone resorption (urinary crosslinks) was higher and bone formation (serum osteocalcin) was lower in obese than in lean rats, whereas Ca balance components and Ca-regulating hormones did not differ. EnR for 10 wk reduced body weight by 25 +/- 7% compared with a 6 +/- 6% gain in CTL rats (P < 0.001). For both lean and obese rats, TFCA (5-d measurement, (45)Ca radioisotope) decreased from 30 +/- 9% to 24 +/- 9% with EnR, compared with 25 +/- 10% to 29 +/- 11% in controls (P < 0.05). Weight loss was directly correlated with the decrease in TFCA (r = 0.34, P < 0.05). Uterine weights indicated a reduced estrogenic activity in energy-restricted rats (P < 0.0001). In lean, but not obese rats, serum estradiol (E(2)) correlated with weight loss (r = 0.52, P < 0.05), and tended to correlate with the decrease in TFCA (r = 0.48, P = 0.06). At the end of the study, serum 25-hydroxyvitamin-D was lower and urinary Ca was higher in lean than obese energy-restricted rats. Distinct endocrine profiles during weight loss in obese and lean rats suggest that the susceptibility of bone and Ca metabolism to EnR could differ depending on initial body weight.

Detecting patients with low skeletal bone mass

OBJECTIVES

The object of this study was to determine the relative usefulness of clinical and radiographic indices in the diagnosis of patients with low skeletal bone mass amongst 135 healthy perimenopausal women, aged 45-55 years, attending for routine dental treatment.

METHODS

Bone mineral density was measured for the spine and femoral neck, using dual energy X-ray absorptiometry. Each patient's osteoporosis status was calculated according to the WHO criteria for Caucasian women. Each patient received a dental panoramic tomogram, and the width of the inferior mandibular cortex (mental index, (MI)) was measured. The body mass index (BMI) and simple calculated osteoporosis risk estimation (SCORE) indices were calculated.

RESULTS

The SCORE index was a significant factor in predicting low bone mass, but with the weight of the patient being the only significant constituent factor. MI, BMI and SCORE indices were significantly correlated with skeletal bone density. When the logistic regression model included MI, BMI and SCORE indices, all three variables were significant predictors of low skeletal bone mass.

CONCLUSIONS

A thinning of the mandibular cortices (MI<3mm) in a normal perimenopausal female is associated with low skeletal bone mass. If, in addition, the patient is underweight (BMI is below 20kg/m(2)) or has a high SCORE index (> or =6) then this increases their risk of osteoporosis.