Prior loss of body mass index, low body mass index, and central obesity independently contribute to higher rates of fractures in elderly women and men

Bone health and body composition in prostate cancer: Meet-URO and AIOM consensus about prevention and management strategies

BACKGROUND

Prostate cancer (PCa) treatments are associated with a detrimental impact on bone health (BH) and body composition. However, the evidence on these issues is limited and contradictory. This consensus, based on the Delphi method, provides further guidance on BH management in PCa.

MATERIALS AND METHODS

In May 2023, a survey made up of 37 questions and 74 statements was developed by a group of oncologists and endocrinologists with expertise in PCa and BH. In June 2023, 67 selected Italian experts, belonging to the Italian scientific societies Italian Association of Medical Oncology and Italian Network for Research in Urologic-Oncology (Meet-URO), were invited by e-mail to complete it, rating their strength of agreement with each statement on a 5-point scale. An agreement ≥75% defined the statement as accepted.

RESULTS

In non-metastatic hormone-sensitive PCa, the panel agreed that androgen deprivation therapy (ADT) alone implies sufficient fracture risk to warrant antifracture therapy with bone-targeting agents (BTAs) for cancer treatment-induced bone loss (CTIBL) prevention (79%). Therefore, no consensus was reached (48%) for the treatment with BTAs of patients receiving short-term ADT (<6 months). All patients receiving active treatment for metastatic hormone-sensitive PCa (75%), non-metastatic castration-resistant PCa (89%) and metastatic castration-resistant PCa (mCRPC) without bone metastases (84%) should be treated with BTAs at the doses and schedule for CTIBL prevention. All mCRPC patients with bone metastasis should be treated with BTAs to reduce skeletal-related events (94%). In all settings, the panel analyzed the type and timing of treatments and examinations to carry out for BH monitoring. The panel agreed on the higher risk of sarcopenic obesity of these patients and its correlation with bone fragility.

CONCLUSIONS

This consensus highlights areas lacking major agreement, like non-metastatic hormone-sensitive prostate cancer patients undergoing short-term ADT. Evaluation of these issues in prospective clinical trials and identification of early biomarkers of bone loss are particularly urgent.

Causal relationships between body mass index, low-density lipoprotein and bone mineral density: Univariable and multivariable Mendelian randomization

SUMMARY

Utilizing the Mendelian randomization technique, this research clarifies the putative causal relationship between body mass index (BMI) andbone mineral density (BMD), and the mediating role of low-density lipoprotein (LDL). The implications of these findings present promising opportunities for enhancing our understanding of complex bone-related characteristics and disorders, offering potential directions for treatment and intervention.

OBJECTIVE

The objective of this study is to examine the correlation between BMI and BMD, while exploring the intermediary role of LDL in mediating the causal impact of BMI on BMD outcomes via Mendelian randomization.

METHODS

In this study, we employed genome-wide association study (GWAS) data on BMI, LDL, and BMD to conduct a comparative analysis using both univariate and multivariate Mendelian randomization.

RESULTS

Our study employed a two-sample Mendelian randomization design. Considering BMI as the exposure and BMD as the outcome, our results suggest that BMI may function as a potential protective factor for BMD (β = 0.05, 95% CI 1.01 to 1.09, P = 0.01). However, when treating LDL as the exposure and BMD as the outcome, our findings indicate LDL as a risk factor for BMD (β = -0.04, 95% CI 0.92 to 0.99, P = 0.04). In our multivariate Mendelian randomization (MVMR) model, the combined influence of BMI and LDL was used as the exposure for BMD outcomes. The analysis pointed towards a substantial protective effect of LDL on BMD (β = 0.08, 95% CI 0.85 to 0.97, P = 0.006). In the analysis of mediation effects, LDL was found to mediate the relationship between BMI and BMD, and the effect was calculated at (β = 0.05, 95% CI 1.052 to 1.048, P = 0.04).

CONCLUSION

Our findings suggest that BMI may be considered a protective factor for BMD, while LDL may act as a risk factor. Moreover, LDL appears to play a mediatory role in the causal influence of BMI on BMD.

Associations of abdominal obesity with different types of bone fractures in adults: A systematic review and dose-response meta-analysis of prospective cohort studies

Findings on the association between abdominal obesity and hip fracture were summarized in a meta-analysis in 2017; however, no study has examined the dose-response association between abdominal fat indices and hip fracture. Also, we found no meta-analysis investigating other types of bone fractures including any vertebral fractures in relation to abdominal obesity. Therefore, the present systematic review and dose-response meta-analysis of prospective cohort studies were conducted to examine the association between abdominal obesity and different types of bone fractures. A comprehensive literature search was done by searching PubMed, Scopus, Web of Science, and Google Scholar until October 2021. In total, 23 articles from prospective cohort studies with a total sample size of 3,456,631 participants were included. During the follow-up periods ranging between 4 and 26 years, 137,989 cases of bone fracture were recorded. After comparing the highest and lowest categories of abdominal fat indices, the summary relative risks (RRs) of any, hip, and vertebral fractures were 0.99 (95% CI: 0.81-1.20), 1.09 (95% CI: 0.82-1.43), and 1.18 (95% CI: 1.05-1.33), respectively, indicating a significant positive association between abdominal obesity and risk of vertebral fracture. In the non-linear dose-response analysis, abdominal obesity based on the waist-to-hip ratio (WHR) was positively associated with an increased risk of hip fracture from 0.7 to 1.1 units of WHR. In the linear analysis, a 10 cm increase in waist circumference (WC) was associated with a 3% higher risk of vertebral fracture. We found no other dose-response association for other types of bone fractures. In conclusion, abdominal obesity may be associated with a higher risk of hip and vertebral fractures.

Impact of body mass index on fracture severity, clinical, radiological and functional outcome in distal radius fractures: a retrospective observational study after surgical treatment

INTRODUCTION

Distal radius fracture (DRF) is one of the three most common fractures of the human body with increasing incidences in all groups of age. Known causes of increasing incidence, such as ageing of the population or increased obesity, have been described and discussed. So far, literature reports ambivalent effects of body mass index (BMI) on bone physiology. It is worthwhile to examine the influence of BMI on the outcome of fractures more detailed. This study aims to investigate the influence of an abnormal BMI on fracture severity and treatment, as well as clinical, radiological, and functional outcome to improve clinical decision making.

MATERIALS AND METHODS

A retrospective observational study was conducted on data obtained from patients, who underwent open reduction and internal fixation (ORIF) of a DRF at a local Level 1 Trauma Center between May 2018 and October 2021. Follow-up examinations were performed approximately 1 year after surgical fracture treatment, during which various questionnaires and functional measurements (CMS, DASH, NRS, ROM) were applied. In addition, postoperative complications were recorded and radiological examinations of the affected hand were performed. After excluding incomplete data sets and applying set exclusion criteria, the complete data of 105 patients were analyzed.

RESULTS

74 patients were female and 31 male with significant difference in mean BMI [p = 0.002; female: 23.8 (SD ± 3.3), men: 26.2 (SD ± 3.9)]. Patients with higher BMI had significantly more severe fractures (p = 0.042). However, there was no significant difference in surgery time for fracture management. At follow-up, patients with lower BMI showed a smaller difference in hand strength between the fractured and the other hand (p = 0.017). The BMI had no significant effect on the clinical and radiological outcome.

CONCLUSION

Despite the ambivalent effects of BMI on the skeletal system, our findings indicate that a higher BMI is associated with more severe DRF. Thereby BMI does not correlate with surgery time for fracture treatment. Furthermore, no evidence of an influence on the clinical and radiological outcome could be detected.

Associations between the VDR Gene rs731236 (TaqI) Polymorphism and Bone Mineral Density in Postmenopausal Women from the RAC-OST-POL

BACKGROUND

Postmenopausal osteoporosis is not only related to hormonal factors but is also associated with environmental and genetic factors. One of the latter is the polymorphism of vitamin D receptor (VDR). The aim of the reported study was to comprehensively analyze the VDR gene polymorphic variants rs731236 (TaqI), rs1544410 (BsmI) and rs7975232 (ApaI) in the Polish population of postmenopausal women.

METHODS

The study group consisted of 611 women after menopause (their median age was 65.82 ± 6.29 years). Each of them underwent bone densitometry (DXA) of the non-dominant femoral neck and total hip with a biochemical analysis of vitamin D3 serum concentration and genotyping of the above-mentioned single nucleotide polymorphisms (SNPs); the obtained results were analyzed in the aspect of waist circumference (WC), body mass index (BMI) and past medical history.

RESULTS

The genotype prevalence rates of all SNPs were compatible with Hardy-Weinberg equilibrium (p > 0.050). Out of the studied polymorphisms, only rs731236 genotype variants affected DXA, with AG heterozygotes showing the worst bone parameters. Neither patient age nor vitamin D3 concentration, BMI, WC or comorbidities was associated with rs731236 genotype.

CONCLUSIONS

Out of the polymorphisms studied, only rs731236 genotypes differed among the DXA results, while the AG heterozygotes were characterized by the lowest median bone mineral density.

Declining hip fracture burden in Sweden 1998-2019 and consequences for projections through 2050

We aimed to estimate the absolute and age-standardized number of hip fractures in Sweden during the past two decades to produce time trends and future projections. We used nationwide register data from 1998 to 2019 and a validated algorithm to calculate the annual absolute and age-standardized number of incident hip fractures over time. The total hip fracture burden was 335,399 incident events over the 22 years, with a change from 16,180 in 1998 to 13,929 in 2019, a 14% decrease. One decade after the index hip fracture event, 80% of the patients had died, and 11% had a new hip fracture. After considering the steady growth of the older population, the decline in the age-standardized number of hip fractures from 1998 through 2019 was 29.2% (95% CI 28.1-30.2%) in women and 29.3% (95% CI 27.5-30.7%) in men. With a continued similar reduction in hip fracture incidence, we can predict that 14,800 hip fractures will occur in 2034 and 12,000 in 2050 despite doubling the oldest old (≥ 80 years). Without an algorithm, a naïve estimate of the total number of hip fractures over the study period was 539,947, with a second 10-year hip fracture risk of 35%. We note an ongoing decline in the absolute and age-standardized actual number of hip fractures in Sweden, with consequences for future projections.

Association of the visceral adiposity index with femur bone mineral density and osteoporosis among the U.S. older adults from NHANES 2005-2020: a cross-sectional study

Background

The visceral adiposity index (VAI) is a marker of abdominal fat distribution and adipose tissue function. However, the association between VAI and femur bone mineral density (BMD) and osteoporosis is unclear among the U.S. older adults.

Methods

Cross-sectional data for adults aged 60 years and older from the 2007-2020 National Health and Nutrition Examination Survey (NHANES) were included. Multivariable linear and logistic regression were used to evaluate the association between VAI and femur BMD and osteoporosis. We used the smooth curve fitting to address nonlinearity. Moreover, a two-piecewise linear regression model was used to explain the nonlinearity further.

Results

The findings of the multivariable logistic regression models showed that as the VAI value increased by one unit, the prevalence of osteoporosis decreased by 1.2% after adjusting for covariates associated with osteoporosis. The multivariable linear regression models demonstrated that VAI was positively correlated with femur BMD. Further analysis revealed an inverted L-shaped and inverted U-shaped relationship between VAI and femur BMD at different sites.

Conclusions

Our findings indicated that an increased VAI is independently linked to a higher prevalence of osteoporosis among the U.S. older adults. Further analysis reveals that once VAI reaches a certain threshold, femur BMD no longer increases and may even decrease. This suggests that a moderate accumulation of visceral fat may be beneficial for bone health, while excessive visceral fat could potentially have detrimental effects.

Comprehensive analyses of circulating cardiometabolic proteins and objective measures of fat mass

BACKGROUND

The underlying molecular pathways for the effect of excess fat mass on cardiometabolic diseases is not well understood. Since body mass index is a suboptimal measure of body fat content, we investigated the relationship of fat mass measured by dual-energy X-ray absorptiometry with circulating cardiometabolic proteins.

METHODS

We used data from a population-based cohort of 4950 Swedish women (55-85 years), divided into discovery and replication samples; 276 proteins were assessed with three Olink Proseek Multiplex panels. We used random forest to identify the most relevant biomarker candidates related to fat mass index (FMI), multivariable linear regression to further investigate the associations between FMI characteristics and circulating proteins adjusted for potential confounders, and principal component analysis (PCA) for the detection of common covariance patterns among the proteins.

RESULTS

Total FMI was associated with 66 proteins following adjustment for multiple testing in discovery and replication multivariable analyses. Five proteins not previously associated with body size were associated with either lower FMI (calsyntenin-2 (CLSTN2), kallikrein-10 (KLK10)), or higher FMI (scavenger receptor cysteine-rich domain-containing group B protein (SSC4D), trem-like transcript 2 protein (TLT-2), and interleukin-6 receptor subunit alpha (IL-6RA)). PCA provided an efficient summary of the main variation in FMI-related circulating proteins involved in glucose and lipid metabolism, appetite regulation, adipocyte differentiation, immune response and inflammation. Similar patterns were observed for regional fat mass measures.

CONCLUSIONS

This is the first large study showing associations between fat mass and circulating cardiometabolic proteins. Proteins not previously linked to body size are implicated in modulation of postsynaptic signals, inflammation, and carcinogenesis.

The association of body composition and fat distribution with dysmobility syndrome in community-dwelling older adults: Bushehr Elderly Health (BEH) program

BACKGROUND AND OBJECTIVE

Dysmobility Syndrome (DS) is characterized as an accumulation of clinical risk factors for functional disability, such as osteoporosis, sarcopenia, and obesity. Neurological disorders that affect the motor and sensory systems can also contribute to the condition, resulting in gait and muscle strength disturbances, as well as a history of falls and fractures. The study aimed to determine the association between fat distribution in different body areas and the odds of older adults developing DS, as there is still uncertainty about the accumulation of fat in which area is most closely linked to the condition.

METHODS

This cross-sectional study was conducted according to the data from the second phase of the Bushehr Elderly Health Cohort (BEH). Dysmobility Syndrome was defined based on the co-occurrence of at least three outcomes of its criteria. Body composition was measured using dual-energy X-ray absorptiometry (DXA) and anthropometric studies. For evaluating the relationship, multivariate logistic regression and adjusted univariate linear regression were used.

RESULTS

Of 2,359 who were recruited in the study, 1,277 participants (54.13%) had DS. According to the final logistic regression model in the limb region, FM and FM to FFM ratios were significantly associated with DS [OR (95%CI) = 1.04 (1.02 to 1.05), and 3.42 (1.95 to 5.99), respectively]. Also, In the trunk region, the FM and FM to FFM ratio were significantly related to the odds of DS, although this relationship was weaker than in the limbs region [OR (95%CI) = 1.02 (1.00 to 1.03), and 2.45 (1.36 to 4.39), respectively].

CONCLUSION

Our findings indicate that a higher regional and whole-body amount of fat mass rather than fat-free mass is closely linked to an increased risk of DS, particularly in the elderly population. Notably, higher fat mass in the limbs (especially in the legs) is associated with greater odds of DS, while a higher android-to-gynoid fat mass ratio is associated with lower DS risk. Screening fat mass distribution in older individuals can be a valuable strategy for promptly diagnosing DS, implementing interventions to prevent disabilities, and improving their quality of life.

Impact of leptin deficiency on male tibia and vertebral body 3D bone architecture independent of changes in body weight

Leptin an adipokine with potent effects on energy balance and body weight plays an important role in defining bone architecture in growing mammals. However, major changes in body weight can also influence morphology of trabecular and cortical bone. Therefore, we examined the impact of leptin deficiency on tibia and vertebral body 3D bone architecture independent of changes in body weight. Furthermore, advances in computational 3D image analysis suggest that average morphological values may mask regional specific differences in trabecular bone thickness. The study utilized leptin-deficient Ob/Ob mice (n = 8) weight-paired to C57BL/6 (C57) control mice (n = 8) which were split into either lean or obese groups for 24 ± 2 weeks. Whole tibias and L3 vertebrae were fixed before high resolution microcomputed tomography (μCT) scanning was performed. Leptin deficiency independent of body weight reduced tibia cortical bone volume, trabecular bone volume/tissue volume, number, and mineral density. Mean tibia trabecular thickness showed no significant differences between all groups; however, significant changes in trabecular thickness were found when analyzed by region. This study demonstrates that leptin deficiency significantly impacts tibia and vertebral body trabecular and cortical bone 3D architecture independent of changes in body weight.

Age-specific effects of weight-based body size on fracture risk in later life: a lifecourse Mendelian randomisation study

Musculoskeletal conditions, including fractures, can have severe and long-lasting consequences. Higher body mass index in adulthood is widely acknowledged to be protective for most fracture sites. However, sources of bias induced by confounding factors may have distorted previous findings. Employing a lifecourse Mendelian randomisation (MR) approach by using genetic instruments to separate effects at different life stages, this investigation aims to explore how prepubertal and adult body size independently influence fracture risk in later life.Using data from a large prospective cohort, univariable and multivariable MR were conducted to simultaneously estimate the effects of age-specific genetic proxies for body size (n = 453,169) on fracture risk (n = 416,795). A two-step MR framework was additionally applied to elucidate potential mediators. Univariable and multivariable MR indicated strong evidence that higher body size in childhood reduced fracture risk (OR, 95% CI: 0.89, 0.82 to 0.96, P = 0.005 and 0.76, 0.69 to 0.85, P = 1 × 10- 6, respectively). Conversely, higher body size in adulthood increased fracture risk (OR, 95% CI: 1.08, 1.01 to 1.16, P = 0.023 and 1.26, 1.14 to 1.38, P = 2 × 10- 6, respectively). Two-step MR analyses suggested that the effect of higher body size in childhood on reduced fracture risk was mediated by its influence on higher estimated bone mineral density (eBMD) in adulthood.This investigation provides novel evidence that higher body size in childhood reduces fracture risk in later life through its influence on increased eBMD. From a public health perspective, this relationship is complex since obesity in adulthood remains a major risk factor for co-morbidities. Results additionally indicate that higher body size in adulthood is a risk factor for fractures. Protective effect estimates previously observed are likely attributed to childhood effects.

Associations of visceral adipose tissue with bone mineral density and fracture: observational and Mendelian randomization studies

BACKGROUND

The associations between visceral adipose tissue (VAT) and bone mineral density (BMD) or fracture have been controversial and the causality of the associations remains to be assessed. This study aimed to explore the associations of VAT^ (predicted value of VAT mass) with BMD and fracture risk in men and women, and to examine their potential causation by two-sample Mendelian randomization (MR) analyses.

METHODS

UK Biobank is a large, population-based prospective cohort study that recruited more than 500,000 participants aged 40-69 in the United Kingdom from 2006 to 2010. In this study, we used a validated and reliable prediction model to estimate the VAT amount of the participants. On this basis, linear and nonlinear multivariable statistical models were used to explore the association of VAT^ with BMD and fracture risk in different groups of sex and BMI. In observational analyses, the multivariable linear regression model and Cox proportional-hazards model were used to assess VAT^ association with BMD and fracture risk, respectively. Inverse variance weighting was used as the main result of MR analysis.

RESULTS

In 190,836 men, an inverted U-shaped association was observed between VAT^ and heel BMD (P for nonlinearity < 0.001), with a turning point of VAT^ = 1.25 kg. Per kg increase in VAT^ was associated with a 0.13 standard deviation (SD) increase in heel BMD (P = 1.5 × 10^-16) among men with lower amounts of VAT^, and associated with a 0.05 SD decrease in heel BMD (P = 1.3 × 10^-15) among men with higher amounts of VAT^. In 193,592 women, per kg increase in VAT^ was monotonically associated with a 0.16 SD increase in heel BMD (P = 1.2 × 10^-136, P for VAT^-sex interaction = 8.4 × 10^-51). During a median follow-up of 8.2 years, VAT^ was associated with lower risks of hip fractures in the overall men and women (P for VAT^-sex interaction = 1.9 × 10^-4 for total fractures; 1.5 × 10^-4 for other fractures). There were significant interactions of VAT^ and BMI on heel BMD and fracture risks in men only (P for VAT^-BMI interaction = 5.9 × 10^-31 for heel BMD; 2.7 × 10^-4 for total fractures; 5.7 × 10^-3 for hip fractures; 6.8 × 10^-3 for other fractures). In two-sample MR analyses, evidence of causality was not observed between VAT^ and DXA-derived BMD or fractures.

CONCLUSIONS

These novel findings demonstrated gender-dependent associations of VAT^ with BMD and fracture risk, with the association in men being modified by adiposity. Evidence of causality was not observed, suggesting that the observational association of VAT^ with BMD and fracture risk could be the result of confounding.

Relationship between oseteoporosis with fatty infiltration of paraspinal muscles based on QCT examination

INTRODUCTION

To investigate the correlation between paraspinal muscles features and osteoporosis in lumbar spine.

MATERIALS AND METHODS

A total of 367 subjects who underwent quantitative computed tomography (QCT) examination were enrolled in this study. QCT pro workstation was used to obtain the mean bone mineral density (BMD) of the lower lumbar spine. Fat fraction (FF) and cross-section area (CSA) of the paraspinal muscles at the corresponding levels were measured. All participants were divided into normal, osteopenia, and osteoporosis groups. One-way ANOVA and independent samples t tests were performed to compare differences between groups. Pearson and Spearman correlation coefficients and partial correlation analysis after controlling for confounding factors were used to analyze the correlation between BMD and paraspinal muscles measurements.

RESULTS

Among the 367 participants included, 116 were in the normal group, 130 in the osteopenia group and 121 in the osteoporosis group. There were significant differences among the three groups for the mean and multifidus FF. BMD showed negative correlations with the FF of the paraspinal muscles. Multifidus and mean FF showed the best correlation (r = - 0.654, - 0.777). There were also significant differences in the mean and multifidus FF between different age groups, while after controlling for confounding factors, there was no correlation between age and FF of the paraspinal muscles.

CONCLUSION

This preliminary study demonstrated the association of BMD with fatty infiltration of paraspinal muscles. Different muscles might have specific effects in different sex and age groups.

Effect of obesity status on adolescent bone mineral density and saturation effect: A cross-sectional study

BACKGROUND

The effect of obesity status on bone mineral density (BMD) in adolescents and whether there is a saturation effect is still insufficient. A cross-sectional study of adolescents aged 12-19 was conducted to investigate them.

METHODS

Weighted multivariate linear regression models were used to assess the relationship between obesity status and BMD via datasets from the National Health and Nutrition Examination Survey 2011-2018. The nonlinear relationships and saturation values were ascertained by fitting smooth curves and analyzing saturation effects. At the same time, the subgroup stratified analysis was also performed.

RESULTS

4056 adolescents were included in this study. We found that body mass index (BMI) and waist circumference (WC) were significantly associated with total BMD, which remained significant in subgroups stratified by age, gender, standing height, and ethnicity. We also noticed an inverse correlation between left leg fat/lean mass and left leg BMD, which was only significant in males and other races. Fitting smooth curve and saturation effect analysis showed that BMI, WC, left leg fat/lean mass, and BMD had a specific saturation effect. There was a saturation effect on bone mineral density in adolescents with a BMI of 22 kg/m², a WC of 70.5 cm, or a left leg fat/lean mass of 0.2994.

CONCLUSIONS

We found a positive saturation effect of BMI and WC with BMD and a negative saturation effect of left leg fat/lean mass with BMD. Appropriate obesity status allows adolescents to have better bone mass development but not excessive obesity.

The Association of Prepregnancy Body Mass Index with Pregnancy Outcomes in Chinese Women

Our study was to evaluate the association between prepregnancy body mass index (BMI) and pregnancy outcomes. A total of 1546 women who attended prenatal care clinics and delivered at the Peking University International Hospital, Beijing, China, from October 2018 to April 2020 was included. This research explored gestational, perinatal, and postpartum outcomes, including gestational diabetes, anemia, preeclampsia, preterm premature rupture of membranes (PPROM), and postpartum hemorrhage. Participants were divided into underweight (BMI < 18.5 kg/m²), normal weight (18.5 kg/m² ≤ BMI ≤ 23.9 kg/m²), overweight (24 kg/m² ≤ BMI ≤ 27.9 kg/m²), and obese (BMI ≥ 28 kg/m²) groups. Logistic regression analysis was used to analyze the association between prepregnancy BMI and pregnancy outcomes, and odds ratio (OR) with 95% confidence interval (95% CI) was calculated. After adjusting potential confounders, the risk of PPROM was higher in the underweight group than the normal weight group (OR = 1.864, 95% CI: 1.269-2.737, P < 0.01). Prepregnancy obesity was associated with higher odds of gestational diabetes (OR = 2.649, 95% CI: 1.701-4.126, P < 0.001) and preeclampsia (OR = 3.654, 95% CI: 1.420-9.404, P < 0.01) than the normal weight group, whereas it correlated with the lower risk of anemia (OR = 0.300, 95% CI: 0.128-0.704, P < 0.01). Our findings may provide evidence for the importance of keeping normal weight for Chinese women when preparing for pregnancy.