Bone minerals changes in obese women during a moderate weight loss with and without calcium supplementation

Messages about calcium and weight in Canadian women's magazines

PURPOSE

Osteoporosis affects 1.4 million Canadians. Maximizing bone mass by age 30 may reduce this risk. Because calcium intake and body weight are both associated with bone mass, and many Canadian women report that they obtain nutrition information from magazines, we compared the frequency of calcium and body weight messages in Chatelaine and Flare, Canadian magazines for mature versus younger women, respectively.

METHODS

Using keywords, we identified relevant advertisements and articles in all issues of Chatelaine and Flare for 2000 to 2001. Data were analyzed using paired t-tests and Wilcoxon signed-rank sum tests.

RESULTS

Chatelaine had more calcium and weight messages per 100 pages than did Flare (significant only for calcium, p <or= 0.0001). Within Chatelaine, there were no significant differences between the frequency of calcium and weight messages; however, almost 90% of Flare's messages focused on weight (p <or= 0.0001), with only eight messages in two years addressing calcium.

CONCLUSIONS

Magazines with limited calcium and many weight messages inadvertently promote a lifestyle that may increase the risk for osteoporosis. The opportunity exists to provide improved calcium and osteoporosis coverage for women at the prime age for maximizing bone density. Awareness of information gaps may help dietitians strategize in promoting nutrition messages to women.

Phosphocalcic Metabolism after Biliopancreatic Diversion

BACKGROUND

Malabsorptive techniques to treat morbid obesity have been followed by alterations in phosphocalcic metabolism. Knowledge of the preoperative situation is important to assess the influence of these techniques on phosphocalcic metabolism and to consider treatments for these alterations.

METHODS

61 consecutive morbidly obese patients (50 women, 11 men, age 19 to 63 years) having had biliopancreatic diversion (BPD) were studied in a prospective manner. Preoperative and postoperative levels of calcium, phosphorus, 25-hydroxyvitamin D, tartrate resistant acid phosphate, plasma parathormone (PTH), tubular absorption of phosphate, and urinary calcium and pyridinolines were analyzed, as well as the potential risk factors for their alterations. Follow-up of all patients was a minimum of 4 years.

RESULTS

Before BPD, 42.3% of patients presented an increase in PTH and 54% a decrease in the 25-OH vitamin D, but the values of calcium and plasma phosphorus maintained at normal level. 81.8% of the patients with an increase in the PTH maintained high levels after BPD, while 60% of those with a normal preoperative PTH also presented hyperparathyroidism 4 years after the intervention. A correlation between the levels of plasma PTH and body mass index was not found.

CONCLUSION

Morbid obesity is accompanied by a high percentage of hyperparathyroidism. BPD produces malabsorption of vitamin D during the first years, favoring the persistence or appearance of hyperparathyroidism. It is important to recognize and treat the secondary hyperparathyroidism. The postoperative period could necessitate more energetic interventions to get more efficient control of the phosphocalcic metabolism.

Premenopausal overweight women do not lose bone during moderate weight loss with adequate or higher calcium intake

BACKGROUND

Weight loss is associated with bone loss, but this has not been examined in overweight premenopausal women.

OBJECTIVE

The aim of this study was to assess whether overweight premenopausal women lose bone with moderate weight loss at recommended or higher than recommended calcium intakes.

DESIGN

Overweight premenopausal women [n = 44; x (+/-SD) age: 38 +/- 6.4 y; body mass index (BMI): 27.7 +/- 2.1 kg/m(2)] were randomly assigned to either a normal (1 g/d) or high (1.8 g/d) calcium intake during 6 mo of energy restriction [weight loss (WL) groups] or were recruited for weight maintenance at 1 g Ca/d intake. Regional bone mineral density and content were measured by dual-energy X-ray absorptiometry, and markers of bone turnover were measured before and after weight loss. True fractional calcium absorption (TFCA) was measured at baseline and during caloric restriction by using a dual-stable calcium isotope method.

RESULTS

The WL groups lost 7.2 +/- 3.3% of initial body weight. No significant decrease in BMD or rise in bone turnover was observed with weight loss at normal or high calcium intake. The group that consumed high calcium showed a strong relation (r = 0.71) between increased femoral neck bone mineral density and increased serum 25-hydroxyvitamin D. No significant effect of weight loss on TFCA was observed, and the total calcium absorbed was adequate at 238 +/- 81 and 310 +/- 91 mg/d for the normal- and high-calcium WL groups, respectively.

CONCLUSION

Overweight premenopausal women do not lose bone during weight loss at the recommended calcium intake, which may be explained by sufficient amounts of absorbed calcium.

A systematic review of the effects of calcium supplementation on body weight

Animal studies and epidemiological studies have suggested that Ca supplementation (with Ca supplements or dairy products) may be associated with weight loss in human adults. We aimed toassess whether any association was present by reviewing relevant randomized controlled trials in human subjects. The study was a systematic review and subsequent meta-analysis of randomized controlled trials that used Ca supplementation as an intervention in persons 18 or more years of age, and that reported body weight as a final outcome. A total of thirteen randomized controlled trials were included in the meta-analysis. There was no association between the increased consumption of either Ca supplements or dairy products and weight loss after adjusting fordifferences in baseline weights between the control and intervention groups (P=0·19 and 0·85, respectively). We therefore concluded that Ca supplementation has no statistically significant association with a reduction in body weight.

Calcium Intake and 10-Year Weight Change in Middle-Aged Adults

OBJECTIVE

The goal of this study was to examine the purported effects of calcium on modulating body weight.

DESIGN

Retrospective data was used to assess the relationship between calcium intake and weight change over an 8- to 12-year period among middle-aged adults.

SUBJECTS

Participants were 10,591 men and women aged 53 to 57 years recruited during 2000-2002.

STATISTICAL ANALYSIS

Linear regression was used to model associations of 10-year weight change and calcium intake, adjusted for weight at age 45 years, energy intake, physical activity, and other factors.

RESULTS

Calcium intake was associated with 10-year weight change only in women. Women with current calcium supplement dose of >500 mg/day had a 10-year weight gain of 5.1 kg (95% confidence interval 4.7 to 5.5) compared to 6.9 kg (95% confidence interval 6.5 to 7.4) among nonusers (P for trend=0.001). Trends were similar for total calcium intake from diet plus supplements (P for trend=0.001). Dietary calcium alone had no significant effect on 10-year weight change.

CONCLUSIONS

Increasing total calcium intake, in the form of calcium supplementation, may be beneficial to weight maintenance, especially in women during midlife.

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, body weight, and weight reduction: what are the concerns?

Of the U.S. population, 65% is either overweight or obese, and weight loss is recommended to reduce co-morbid conditions. However, bone mobilization and loss may also occur with weight loss. The risk for bone loss depends on initial body weight, age, gender, physical activity, and conditions of dieting such as the extent of energy restriction and specific levels of nutrient intake. Older populations are more prone to bone loss with weight loss; in women, this is due at least in part to a reduced dietary Ca intake and/or efficiency of absorption. Potential hormonal mechanisms regulating bone loss during weight loss are discussed, including decreases in estrogen, leptin, glucagon-like peptide-2, growth hormone, and insulin-like growth factor-1, or an increase in cortisol. In contrast, the rise in adiponectin and ghrelin with weight reduction should not be detrimental to bone. Combining energy restriction with exercise does not necessarily prevent bone loss, but may attenuate loss as was shown with additional Ca intake or osteoporosis medications. Future controlled weight loss trials should be designed to further address mechanisms influencing the density and quality of bone sites vulnerable to fracture, in the prevention of osteoporosis.

Weight change in adult life and health outcomes

OBJECTIVE

To investigate the relationship between weight change in adult life and subsequent mortality and cancer incidence in women.

RESEARCH METHODS AND PROCEDURES

In 1994 to 1995, all women (age range, 42 to 81) still under general practitioner observation in the United Kingdom's Royal College of General Practitioners Oral Contraception Study (n = 12,303) were sent a health survey asking about health and lifestyle issues, including current weight and weight at age 30. The main outcome measures were 6-year all-cause mortality and cancer incidence among different weight change deciles. Cox regression was used to calculate hazard ratios that were adjusted for: social class at recruitment, BMI at age 30, and age group, parity, smoking status, and hormone replacement therapy status in 1995.

RESULTS

Women who had been obese at age 30 were more likely to die and significantly more likely to develop cancer in the 6 years after the health survey than non-obese respondents. Women reporting weight gains between age 30 and 1995 were significantly less likely to die during the 6 years after the health survey than those with a stable weight, whereas those with weight loss did not fare any better than those in the stable-weight group.

DISCUSSION

Although obesity at young age was associated with subsequent mortality and cancer incidence, weight gain over a time period of 12 to 51 years appeared to be beneficial when compared with women with stable weight over the same time period. Further research is needed to confirm or refute our findings and to allow detailed examination of potential explanations for them.

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.

Effect of energy-reduced diets high in dairy products and fiber on weight loss in obese adults

OBJECTIVE

Studies suggest that high-dairy and high-fiber/low-glycemic index diets may facilitate weight loss, but data are conflicting. The effects on weight loss and body fat of a high-dairy diet and a diet high in dairy and fiber and low in glycemic index were compared with a standard diet.

RESEARCH METHODS AND PROCEDURES

Ninety obese subjects were recruited into a randomized trial of three diets designed to provide a calorie deficit of 500 calories/d over a 48-week period. The study compared a moderate (not low)-calcium diet with a high-calcium diet.

RESULTS

Seventy-two subjects completed the study. Significant weight and fat loss occurred with all three diets. A diet with 1400 mg of calcium did not result in greater weight (11.8 +/- 6.1 kg) or fat (9.0 +/- 6.0 kg) loss than a diet with 800 mg of calcium (10.0 +/- 6.8 and 7.5 +/- 6.6 kg, respectively). A diet with 1400 mg of calcium, increased fiber content, and fewer high-glycemic index foods did not result in greater weight (10.6 +/- 6.8 kg) or fat (8.5 +/- 7.8 kg) loss than the standard diet with 800 mg of calcium. Lipid profile, high-sensitivity C-reactive protein, leptin, fasting glucose, and insulin improved significantly, but there were no significant differences between the experimental diets and the control diet.

DISCUSSION

We found no evidence that diets higher than 800 mg of calcium in dairy products or higher in fiber and lower in glycemic index enhance weight reduction beyond what is seen with calorie restriction alone.

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.

Effect of calcium and dairy foods in high protein, energy-restricted diets on weight loss and metabolic parameters in overweight adults

OBJECTIVE

To compare the effects two high-protein (HP) diets that differ in dietary calcium and protein source on weight loss, body composition, glucose and lipid metabolism, markers of liver function, fibrinolysis and endothelial function and blood pressure.

DESIGN

Randomized, parallel study (12 wk of energy restriction, 4 wk of energy balance) of high dairy protein/high-calcium (DP, 2400 mg Ca/d) and high mixed protein/moderate calcium (MP, 500 mg Ca/d) diets (5.5 MJ/d, 34% protein, 41% carbohydrate, 24% fat).

SUBJECTS

In all, 50 healthy, overweight (age 25-64 y; body mass index 25-35 kg/m(2);) males (n=20) and females (n=30).

RESULTS

Loss of total weight (-9.7+/-3.8 kg), fat mass (-8.3+/-0.4 kg) and lean mass (-1.6+/-0.3 kg) were independent of dietary group. Improvements in fasting insulin, lipids, systolic/diastolic blood pressure, and markers of liver function, fibrinolysis and endothelial function were independent of dietary intervention.

CONCLUSIONS

Increased dietary calcium/dairy foods in an energy-restricted, HP diet does not affect weight loss or body composition. Weight reduction following increased protein diets is associated with beneficial metabolic outcomes that are not affected by protein source.

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.

Effects of calcium supplementation on body weight and blood pressure in normal older women: a randomized controlled trial

CONTEXT

Epidemiological data suggest that high calcium intakes are associated with decreased body weight and blood pressure. However, there is little evidence from randomized trials that addresses these important issues.

OBJECTIVE

The objective of this study was to assess the long-term effects of calcium on body weight and blood pressure.

DESIGN

This is a substudy of an ongoing, double-blind, randomized, controlled trial of calcium supplementation. End points were assessed at 30 months.

SETTING

This study was performed at a university medical center.

PARTICIPANTS

Normal postmenopausal women (mean age, 74 yr; mean weight, 67 kg; mean blood pressure, 134/70 mm Hg at baseline) participated in this study.

INTERVENTION

Study subjects were treated with calcium (1 g/d; n = 732) and placebo (n = 739).

MAIN OUTCOME MEASURES

Body weight and blood pressure were the main outcome measures.

RESULTS

Weight decreased by 368 +/- 132 g (mean +/- se) with calcium treatment and by 369 +/- 134 g with placebo (P = 0.93). Fat and lean masses did not show an effect of calcium. Blood pressure showed transient reductions of 1-2 mm Hg at 6 months in the calcium group, resulting in a significant between-group difference only for systolic pressure (P = 0.048). At 30 months, the change from baseline in systolic pressure was 0.0 +/- 0.9 mm Hg in the calcium group and 2.4 +/- 0.9 mm Hg in the placebo group (P = 0.14). For diastolic pressures, the changes were -0.2 +/- 0.4 and 0.8 +/- 0.4 mm Hg, respectively (P = 0.13). In those with baseline calcium intakes less than 600 mg/d, the treatment effect was greater and did persist.

CONCLUSIONS

Calcium supplementation of 1 g/d does not produce biologically significant effects on body weight, and its hypotensive effect is small and transient in most women.

Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women

BACKGROUND

Limited evidence suggests that a higher ratio of protein to carbohydrate during weight loss has metabolic advantages.

OBJECTIVE

The objective was to evaluate the effects of a diet with a high ratio of protein to carbohydrate during weight loss on body composition, cardiovascular disease risk, nutritional status, and markers of bone turnover and renal function in overweight women.

DESIGN

The subjects were randomly assigned to 1 of 2 isocaloric 5600-kJ dietary interventions for 12 wk according to a parallel design: a high-protein (HP) or a high-carbohydrate (HC) diet.

RESULTS

One hundred women with a mean (+/-SD) body mass index (in kg/m(2)) of 32 +/- 6 and age of 49 +/- 9 y completed the study. Weight loss was 7.3 +/- 0.3 kg with both diets. Subjects with high serum triacylglycerol (>1.5 mmol/L) lost more fat mass with the HP than with the HC diet (x +/- SEM: 6.4 +/- 0.7 and 3.4 +/- 0.7 kg, respectively; P = 0.035) and had a greater decrease in triacylglycerol concentrations with the HP (-0.59 +/- 0.19 mmol/L) than with the HC (-0.03 +/- 0.04 mmol/L) diet (P = 0.023 for diet x triacylglycerol interaction). Triacylglycerol concentrations decreased more with the HP (0.30 +/- 0.10 mmol/L) than with the HC (0.10 +/- 0.06 mmol/L) diet (P = 0.007). Fasting LDL-cholesterol, HDL-cholesterol, glucose, insulin, free fatty acid, and C-reactive protein concentrations decreased with weight loss. Serum vitamin B-12 increased 9% with the HP diet and decreased 13% with the HC diet (P < 0.0001 between diets). Folate and vitamin B-6 increased with both diets; homocysteine did not change significantly. Bone turnover markers increased 8-12% and calcium excretion decreased by 0.8 mmol/d (P < 0.01). Creatinine clearance decreased from 82 +/- 3.3 to 75 +/- 3.0 mL/min (P = 0.002).

CONCLUSION

An energy-restricted, high-protein, low-fat diet provides nutritional and metabolic benefits that are equal to and sometimes greater than those observed with a high-carbohydrate diet.

[Role of calcium intake in obesity]

Recent evidences from epidemiological and intervention trials suggest that a higher calcium intake is associated with a lower body weight and a reduction in total and central body fat. The potential role of calcium intake in the regulation of body adiposity has been explained by the intracellular calcium, which is able to promote adipocyte fat accumulation by exerting a coordinate regulation stimulating lipogenesis and suppressing lipolysis. Moreover, the intracellular calcium has been implicated on the etiopathogenesis of hypertension, insulin resistance and dyslipidemia, appearing as a potential common substrate in the metabolic syndrome. Dietary modulation of intracellular calcium through calciotropic hormones opens an exciting possibility to prevent and tackle obesity and its associated complications by increasing the calcium intake. However, available evidences are mostly indirect and further studies specifically designed for this purpose are needed.

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.

Metabolic complications of bariatric surgery: diagnosis and management issues

Acute complications after bariatric surgery include rhabdomyolysis and immobilization hypercalcemia. The most common long-term metabolic complications following bariatric surgery are anemia and metabolic bone disease. Neuropathy, acute Wemicke's encephalopathy and vitamin A deficiency also occur. Prevention, diagnosis,and treatment of these disorders are necessary parts of lifelong care after bariatric surgery.

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.

Physical frailty and body composition in obese elderly men and women

OBJECTIVE

To evaluate the prevalence of frailty and interrelationships among body composition, physical function, and quality of life in community-dwelling obese elderly (OE) persons.

RESEARCH METHODS AND PROCEDURES

Fifty-two OE, 52 nonobese frail, and 52 nonobese nonfrail subjects, matched for age and sex, were studied. Subjective and objective measures of functional status were evaluated by using the physical performance test, exercise stress test, lower extremity (LE) strength, gait speed, static and dynamic balance, functional status questionnaires, and health-related quality-of-life questionnaire (Medical Outcomes Short Form). Body composition was evaluated by using DXA, and muscle quality was evaluated by determining the ratio of LE strength to LE lean mass.

RESULTS

Among OE subjects, 96% met our standard criteria for mild to moderate frailty. Compared with the nonobese nonfrail group, the OE and nonobese frail groups had lower and similar scores in physical performance test, peak aerobic power, and functional status questionnaire, and exhibited similar impairments in strength, walking speed, balance, and health-related quality of life. Although absolute fat-free mass (FFM) was greater, the percentage body weight as FFM and muscle quality was lower in the OE group than in the other two groups.

DISCUSSION

Physical frailty, which predisposes to loss of independence, is common in community-living OE men and women. Physical frailty in OE subjects was associated with low percentage FFM, poor muscle quality, and decreased quality of life. These findings suggest that weight loss therapy may be particularly important in OE persons to improve physical function, in addition to improving the medical complications associated with obesity.

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.

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.

Bone and gastric bypass surgery: effects of dietary calcium and vitamin D

OBJECTIVE

To examine bone mass and metabolism in women who had previously undergone Roux-en-Y gastric bypass (RYGB) and determine the effect of supplementation with calcium (Ca) and vitamin D.

RESEARCH METHODS AND PROCEDURES

Bone mineral density and bone mineral content (BMC) were examined in 44 RYGB women (> or = 3 years post-surgery; 31% weight loss; BMI, 34 kg/m(2)) and compared with age- and weight-matched control (CNT) women (n = 65). In a separate analysis, RYGB women who presented with low bone mass (n = 13) were supplemented to a total 1.2 g Ca/d and 8 microg vitamin D/d over 6 months and compared with an unsupplemented CNT group (n = 13). Bone mass and turnover and serum parathyroid hormone (PTH) and 25-hydroxyvitamin D were measured.

RESULTS

Bone mass did not differ between premenopausal RYGB and CNT women (42 +/- 5 years), whereas postmenopausal RYGB women (55 +/- 7 years) had higher bone mineral density and BMC at the lumbar spine and lower BMC at the femoral neck. Before and after dietary supplementation, bone mass was similar, and serum PTH and markers of bone resorption were higher (p < 0.001) in RYGB compared with CNT women and did not change significantly after supplementation.

DISCUSSION

Postmenopausal RYGB women show evidence of secondary hyperparathyroidism, elevated bone resorption, and patterns of bone loss (reduced femoral neck and higher lumbar spine) similar to other subjects with hyperparathyroidism. Although a modest increase in Ca or vitamin D does not suppress PTH or bone resorption, it is possible that greater dietary supplementation may be beneficial.

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.

Intentional and unintentional weight loss increase bone loss and hip fracture risk in older women

OBJECTIVES

To test the hypothesis that unintentional weight loss increases the rate of bone loss and risk of hip fracture more than intentional weight loss.

DESIGN

Prospective cohort study.

SETTING

Four communities within the United States.

PARTICIPANTS

Six thousand seven hundred eighty-five elderly white women with measurement of weight change and assessment of intention to lose weight.

MEASUREMENTS

Weight change between baseline and fourth examinations (average 5.7 years between examinations) and assessment of intention to lose weight. Weight loss was defined as a decrease of 5% or more from baseline weight, stable weight was defined as less than a 5% change from baseline weight, and weight gain was defined as an increase of 5% or more from baseline weight. Rate of change in bone mineral density at the hip between fourth and sixth examinations (average 4.4 years between examinations) was measured using dual-energy x-ray absorptiometry. Incident hip fractures occurring after the fourth examination until June 1, 2001 (average follow-up 6.6 years) was confirmed using radiographic reports.

RESULTS

The adjusted average rate of decline in total hipbone density steadily increased from -0.52% per year in women with weight gain to -0.68% per year in women with stable weight to -0.92% per year in women with weight loss (P-value for trend <.001). Higher rates of hip-bone loss were observed in women with weight loss irrespective of body mass index (BMI) or intention to lose weight. During follow-up of an average 6.6 years after the fourth examination, 400 (6%) of the cohort suffered a first hip fracture. Women with weight loss had 1.8 times the risk (95% confidence interval (CI)=1.43-2.24) of subsequent hip fracture as those with stable or increasing weight. The association between weight loss and increased risk of hip fracture was consistent across categories of BMI and intention to lose weight. Even voluntary weight loss in overweight women with a BMI of 25.9 kg/m2 (median) or greater increased the risk of hip fracture (multivariate hazard ratio=2.48, 95% CI=1.33-4.62).

CONCLUSION

Older women who experience weight loss in later years have increased rates of hip-bone loss and a two-fold greater risk of subsequent hip fracture, irrespective of current weight or intention to lose weight. These findings indicate that even voluntary weight loss in overweight elderly women increases hip fracture risk.

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.

No effect of dietary calcium on body weight of lean and obese mice and rats

Recent epidemiological and animal studies have led to the hypothesis that low dietary calcium intakes contribute to obesity. Here, we evaluated whether calcium influenced the body weight of normal-weight and obese rodents. All experiments involved female C57BL/6J mice or Sprague-Dawley rats fed normal- or high-energy-density diets (3.8 o 4.7 kcal/g). Calcium intake was manipulated by allowing mice to drink sweetened 30 mM CaCl(2) solution or feeding mice and rats diets differing in calcium content (0.2%, 0.6%, o 1.8% Ca(2+)). Blood samples were taken from rats to confirm that the diets had their intended effects on metabolism. There were no effects of the calcium manipulations on energy intake, body weight, or carcass fat content and no simple elation between calciotropic hormones and body weight. One experiment found a significant decrease in body weight gain of lean and obese rats fed the 1.8% Ca(2+) diet, but we suspect that this was due to forced consumption of the unpalatable diet, reducing growth. These studies provide little support for the hypothesis that dietary calcium contributes to the etiology or maintenance of obesity.

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.

Calcium intake and adiposity

Limited epidemiologic and experimental data support the possibility that dietary calcium intake plays a role in human body weight regulation. The aim of this review was to present the data from human studies that link calcium and dairy intake to body weight, describe the existing evidence for an effect of calcium intake on body weight from animal models of obesity, present evidence of a role for intracellular calcium in the regulation of lipogenesis and lipolysis, elucidate the potential suggested relation between dietary calcium intake and intracellular calcium concentrations, and outline the effects of calcium supplementation on dietary fat absorption. We suggest that these data support the need for large, population based clinical trials to assess the effects of supplemental calcium and other components of dairy products on human body weight.

Increased dairy product or calcium intake: is body weight or composition affected in humans?

To assess the possible impact of increased intakes of dairy products or calcium on body weight or composition, a MEDLINE search was conducted to identify randomized trials of supplementation with calcium or dairy products. Nine studies of dairy product supplementation were located: In seven, no significant differences in the change in body weight or composition were detected between treatment and control groups. However, two studies conducted in older adults observed significantly greater weight gain in the dairy product groups. The interpretation of these findings is complicated by the inability to accurately determine the extent of dietary compensation for the increment in energy intake provided by the added dairy products. This is not an issue in the interpretation of studies of calcium supplementation, of which 17 were identified. Only one study found greater weight loss in the supplemented group; in the remaining studies, changes in body weight and/or body fat were strikingly similar between groups. In conclusion, the data available from randomized trials of dairy product or calcium supplementation provide little support for an effect in reducing body weight or fat mass. However, the studies reviewed were not specifically designed or powered to address this issue; such studies are required.

Microgravity as a model of ageing

PURPOSE OF REVIEW

Longevity with good health and long-term survival in space are two of the many challenges that scientists face in the twenty-first century. Ageing and life in space are both associated with undesirable effects on normal physiological processes. This review will outline how the endocrine, metabolic, immune and musculoskeletal systems are affected by microgravity and ageing, drawing analogies between the observed changes in an attempt to highlight common mechanisms.

RECENT FINDINGS

Mild hypothyroidism, increased stress hormones (mainly catecholamines), decreased sex steroids, insulin resistance, impaired anabolic response to food intake, anorexia, altered mitochondrial function and systemic inflammatory response are common features of both ageing and microgravity. Both conditions lead to progressive bone and muscle atrophy, compromising mobility and the ability to perform essential daily tasks. In skeletal muscle, both ageing and space flight lead to weakness from whole muscle to single fibre level, accompanied by marked alterations in muscle architecture and in tendon mechanical properties.

SUMMARY

What makes microgravity an interesting and unique tool for gerontologists is that many space-related physiological changes resemble those observed during ageing, but are more or less quickly restored after re-entry, thus allowing the biology of ageing to be investigated both ways, not only during its development but also during recovery.

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.