Obesity and kidney transplantation

Risk factors for delayed graft function in patients with kidney transplantation: a systematic review and meta-analysis

BACKGROUND

Delayed graft function (DGF) continues to represent one of the most frequently encountered early complications following kidney transplantation. Despite notable progress in donor and recipient pretreatment protocols, diagnostic techniques and therapeutic approaches, the incidence of DGF, along with its associated short- and long-term sequelae, has not demonstrated a significant reduction. DGF is influenced by a multitude of factors, and individuals with exposure to these risk factors exhibit a markedly increased probability of developing DGF.

OBJECTIVES

To systematically identify and evaluate risk factors associated with DGF in kidney transplant recipients.

DESIGN

A systematic review and meta-analysis DATA SOURCES: A comprehensive search was performed across multiple databases, including PubMed, Embase, The Cochrane Library, Web of Science, CNKI, Wanfang, VIP and SinoMed, from the inception of each database until 1 March 2024.

PRIMARY OUTCOME MEASURES

OR and OR 95% CI of risk factors for DGF.

RESULTS

The meta-analysis included 19 studies involving a total of 153 008 patients, of whom 96 596 (63.1%) developed DGF. The following risk factors for DGF were identified: prolonged cold ischaemia time (CIT) (OR=1.05, 95% CI=1.03 to 1.07, p<0.0001), elevated donor end-stage serum creatinine (OR=1.54, 95% CI=1.26 to 1.87, p<0.0001), extended dialysis vintage (OR=1.02, 95% CI=1.00 to 1.02, p=0.014), increased human leucocyte antigen (HLA) mismatch number (OR=1.19, 95% CI=1.06 to 1.33, p=0.004), higher donor body mass index (BMI) (OR=1.07, 95% CI=1.03 to 1.11, p<0.0001), advanced donor age (OR=1.02, 95% CI=1.01 to 1.03, p=0.003) and recipient diabetes mellitus (OR=1.52, 95% CI=1.40 to 1.64, p<0.0001).

CONCLUSION

This meta-analysis identified seven significant risk factors for DGF, including prolonged CIT, elevated donor end-stage serum creatinine, extended dialysis vintage, increased HLA mismatch number, higher donor BMI, advanced donor age and recipient diabetes mellitus. These findings may offer potential insights for developing clinical strategies to mitigate the risk of DGF in kidney transplant recipients and improve postoperative management.

PROSPERO REGISTRATION NUMBER

CRD42024520542.

The Relationship Between Weight Indices and Blood Levels of Immunosuppressive Drugs in Renal Transplant Recipients

Background

Calcineurin inhibitors and mammalian target of rapamycin (mTOR) inhibitors are essential for maintaining transplanted organs. However, determining the appropriate dosage and predicting blood concentrations of these drugs based solely on net body weight may be inadequate. Previous studies have presented contradictory results regarding the impact of obesity on drug concentrations and transplant success.

Objectives

This study aims to evaluate various weight indices to identify the most reliable indicator of weight that correlates with the blood levels of drugs used in organ transplantation.

Methods

This retrospective descriptive study included patients from nephrology clinics affiliated with Isfahan University of Medical Sciences who were taking calcineurin and/or mTOR inhibitor drugs. Data extracted from medical records included demographic and clinical information, such as height, weight, and various weight indices (total/ideal/adjusted body weight, lean body mass (LBM), Body Mass Index, and predicted normal weight), as well as blood levels of immunosuppressive drugs at each patient's visit. The dosages of each drug (mg/kg) were analyzed to determine which weight indices best correlated with the obtained blood concentrations, using the Generalized Estimating Equation (GEE) model with logistic regression, an independent correlation matrix, and a binary distribution for data analysis.

Results

The study analyzed the medical records of 71 patients. Trough (C0) concentrations of drugs were evaluated in relation to each weight index, and odds ratios (OR) were calculated for statistical comparison. All weight indices increased the likelihood of achieving appropriate concentrations for cyclosporine, tacrolimus, and sirolimus. Drug dosing based on LBM (OR: 1.028), ideal body weight (OR: 1.075), and total body weight (OR: 1.041) showed the strongest correlations with achieving proper blood levels for cyclosporine, tacrolimus, and sirolimus, respectively.

Conclusions

Integrating various weight indices for calculating individualized doses (mg/kg) of each immunosuppressive drug increases the likelihood of achieving appropriate blood concentrations. However, the optimal weight index varies for each drug. Further studies, particularly those incorporating therapeutic drug monitoring (TDM) plans in transplant centers, are warranted to validate and generalize these findings, providing a potential avenue for improving immunosuppressive therapy and enhancing transplant outcomes.

Weighing the risks: Morbid obesity and diabetes are associated with increased risk of death on the liver transplant waiting list

BACKGROUND & AIMS

Obesity is a growing problem in liver transplant (LT) candidates, paralleling the US obesity epidemic and increase in LT for non-alcoholic steatohepatitis (NASH). While post-LT survival appears to be similar in obese and non-obese patients, data are scarce regarding risk of waitlist dropout in patients with morbid obesity (BMI ≥ 40 kg/m² ). We examined the impact of obesity on waitlist mortality and evaluated predictors of dropout in LT candidates with morbid obesity or NASH.

METHODS

Competing risk analyses were performed in candidates listed between 3/2002-12/2013 to evaluate predictors of waitlist removal or death. Variables with P-value <.05 in univariable models or clinically relevant were included in multivariable models.

RESULTS

Eighty-four thousand two hundred and fifty-four patients (34% female, median age 55, 15% Hispanic) were included. Compared to those with BMI 25-29.9 kg/m² , candidates with BMI ≥ 40 kg/m² were more likely to be female (46% vs 28%), diabetic (25% vs 18%) and have NASH (35% vs 13%); all P < .001. After adjusting for well-recognized predictors of waitlist dropout, including ascites severity, morbid obesity (HR = 1.27, CI 1.20-1.36) and diabetes (HR = 1.14, CI 1.11-1.17) were independent predictors of dropout. Morbid obesity remained a predictor (HR = 1.27, CI 1.10-1.47) of dropout in patients without ascites (24%). In NASH patients, morbid obesity (HR = 1.21, CI 1.07-1.37) and diabetes (HR = 1.15, CI 1.06-1.23) were also associated with a higher dropout risk. In patients with morbid obesity, diabetes trended towards a higher dropout risk but was not significant (HR = 1.12, CI 0.995-1.26).

CONCLUSIONS

Morbid obesity and diabetes are independent predictors of death in LT candidates.

Bariatric Surgery in Renal Transplant Patients

OBJECTIVES

The idea of transplanting organs is not new, nor is the disease of obesity. Obese transplant recipients have greater risk of early death than their cohorts, which is not due to increased rejection but due to obesity-related complications, including arterial hypertension, diabetes, and delayed graft function. Here, our aim was to evaluate the effects of bariatric surgery versus lifestyle changes on outcomes of moderate to severely obese renal transplant recipients.

MATERIALS AND METHODS

Twenty-two morbidly obese patients with stable graft function who underwent bariatric surgery were compared with 44 obese patients on lifestyle management (control group). Both groups were evaluated regarding graft and patient outcomes.

RESULTS

The studied groups were comparable demographically. In the bariatric study group versus control group, we observed that the mean body mass index was 38.49 ± 9.1 versus 44.24 ± 6 (P = .024) at transplant and 34.34 ± 7.6 versus 44.38 ± 6.7 (P = .002) at 6 months of bariatric surgery. Both groups received a more potent induction immunosuppression, but this was significantly higher in the obese nonbariatric control group (P < .05). There were more patients with slow and delayed graft functions in the same nonbariatric group. The 2 groups were comparable regarding new-onset diabetes after transplant, total patients with diabetes, and graft outcomes (P > .05).

CONCLUSIONS

Bariatric surgeries are feasible, safe pro cedures for selected obese renal transplant recipients.

Body mass index and outcome in renal transplant recipients: a systematic review and meta-analysis

BACKGROUND

Whether overweight or obese end stage renal disease (ESRD) patients are suitable for renal transplantation (RT) is often debated. The objective of this review and meta-analysis was to systematically investigate the outcome of low versus high BMI recipients after RT.

METHODS

Comprehensive searches were conducted in MEDLINE OvidSP, Web of Science, Google Scholar, Embase, and CENTRAL (the Cochrane Library 2014, issue 8). We reviewed four major guidelines that are available regarding (potential) RT recipients. The methodology was in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and written based on the PRISMA statement. The quality assessment of studies was performed by using the GRADE tool. A meta-analysis was performed using Review Manager 5.3. Random-effects models were used.

RESULTS

After identifying 5,526 studies addressing this topic, 56 studies were included. We extracted data for 37 outcome measures (including data of more than 209,000 RT recipients), of which 26 could be meta-analysed. The following outcome measures demonstrated significant differences in favour of low BMI (<30) recipients: mortality (RR = 1.52), delayed graft function (RR = 1.52), acute rejection (RR = 1.17), 1-, 2-, and 3-year graft survival (RR = 0.97, 0.95, and 0.97), 1-, 2-, and 3-year patient survival (RR = 0.99, 0.99, and 0.99), wound infection and dehiscence (RR = 3.13 and 4.85), NODAT (RR = 2.24), length of hospital stay (2.31 days), operation duration (0.77 hours), hypertension (RR = 1.35), and incisional hernia (RR = 2.72). However, patient survival expressed in hazard ratios was in significant favour of high BMI recipients. Differences in other outcome parameters were not significant.

CONCLUSIONS

Several of the pooled outcome measurements show significant benefits for 'low' BMI (<30) recipients. Therefore, we postulate that ESRD patients with a BMI >30 preferably should lose weight prior to RT. If this cannot be achieved with common measures, in morbidly obese RT candidates, bariatric surgery could be considered.

Diabetes mellitus, and not obesity, is associated with lower survival following liver transplantation

BACKGROUND AND AIMS

The impact of obesity on survival following liver transplantation is unclear, and existing studies report conflicting results. Our current study aims to further delineate the impact of obesity using population-based registry data from the USA.

METHODS

All US adult liver transplant recipients from 2003 to 2012 were evaluated using the United Network for Organ Sharing registry. The impact of obesity on survival following liver transplantation was further stratified into class I obesity [body mass index (BMI) 30.0-34.9 kg/m(2)], class II obesity (BMI 35.0-39.9 kg/m(2)), and class III obesity (BMI ≥ 40 kg/m(2)) and evaluated using Kaplan-Meier methods and multivariate Cox proportional hazards models.

RESULTS

Overall, 57,255 patients with chronic liver disease underwent liver transplantation, among which 32.9 % had BMI ≥ 30 kg/m(2). While patients in all obesity classes had similar survival to patients with BMI 18.0-24.9 kg/m(2), the presence of concurrent diabetes mellitus resulted in significantly lower post-transplant survival. After multivariate regression, post-transplant survival in patients with class II obesity (HR 0.97; 95 % CI 0.89-1.05) or class III obesity (HR 0.99; 95 % CI 0.90-1.09) was not significantly lower than patients with BMI 18.0-24.9 kg/m(2), but diabetes mellitus was independently associated with lower post-transplant survival (HR 1.29; 95 % CI 1.21-1.36).

CONCLUSION

In conclusion, obesity alone was not associated with lower post-transplant survival. However, DM, either alone or comorbid with obesity, is associated with significantly greater post-transplant mortality.

[Is obesity a barrier to kidney transplantation?]

INTRODUCTION

Kidney transplantation is the most suitable of ESRD care. The proportion of obese people is increasing in the general population and patients with kidney impairment. It is important to assess the impact of obesity on surgical complications of kidney transplantation. The aim of this retrospective study was to signify the correlation between obesity and the occurrence of postoperative urological complications during the first year.

METHODS

We conducted a retrospective study from March 1999 to December 2009. We conducted a chart review of patients undergoing kidney transplantation. The kidneys were taken from cadaveric donors. Data collected included age, weight, height, preoperative BMI; causal nephropathy, smoking, hypertension, diabetes, anticoagulation therapy. Intraoperative data included operative time (DO), cold ischemia. Urological complications were recorded during the first year after the kidney transplantation (vascular anastomotic strictures, ureterovesical stenosis, lymphorrheas, pyelonephritis, hematoma, wound infection). Statistical analysis consisted of a t-test for independent samples and univariate and multivariate logistic regression for the occurrence of complications.

RESULTS

Four hundred and twenty-two patients were transplanted in total. We excluded 20 patients. BMI and duration of surgery patients with complications were significantly different from those of patients with no complications (P=0.016 and P=0.039, respectively). Obese (n=48) had more diabetes (12.5% versus 3.7%, P=0.014), were more often smoking (35.4% versus 22%, P=0.012), had a longer DO (203.64minutes versus 182.46minutes, P=0.006), and complications (62.5% versus 50.28%, P=0.03) than patients with a BMI <30 (n=354). After adjusting for age, smoking, DO, diabetes and BMI showed that only BMI was an independent predictor of the occurrence of postoperative complications with P=0.048 and RR=1.058 [CI: 1 to 1.119]. However, there was no more transplantectomy obese (P=0.911).

CONCLUSION

Our study showed that there is a significant risk of surgical complications after kidney transplantation in obese patients. But ultimately, this does not affect graft survival because there are no more transplantectomies or return to dialysis.

LEVEL OF EVIDENCE

5.

[Metabolic complications after renal transplantation from a living donor: experience of the Ibn Sina university hospital of Rabat]

La transplantation rénale (TR) constitue le traitement de choix de l'insuffisance rénale chronique terminale. Les complications métaboliques après TR (diabète, dyslipidémie, hyperuricémie, obésité), en grande partie liées au traitement immunosuppresseur, deviennent une préoccupation car elles constituent un facteur de risque de morbimortalité et de perte fonctionnelle du greffon. Le but de notre étude est d’évaluer la fréquence de ces anomalies après TR. Il s'agit d'une étude rétrospective incluant tous les patients ayant bénéficié d'une première TR par donneur vivant (DV) de Juin 1998 à Décembre 2010. Nous avons recensé les données démographiques propres au receveur, le traitement immunosuppresseur après TR. Les paramètres clinico-biologiques recueillis sont (index de masse corporel (IMC), glycémie à jeun, hémoglobine glyquée, CT, C-HDL, C-LDL, TG, acide urique). Soixante dix patients ont été colligés, l’âge moyen est de 36.3 + /-9.6 ans (21 à 62) avec un sex ratio de 0.5. Quinze patients (21.4%) étaient hypertendus avant la TR et 2.9% avaient une néphropathie diabétiques. L’âge moyen du donneur est de 47.5 + /-10.2 ans (20-65). Le traitement immunosuppresseur pendant la phase d'induction était une trithérapie associant corticostéroïdes, anticalcineurines chez tous les patients et mycophénolate mofétil chez 68.6% et azathioprine dans 31.4% des cas. L'IMC moyen était de 24.1 + /-4.0 (16.9 à 37), 33% des patients étaient considérés en surpoids dont 21.8% en obésité. L'hypercholestérolémie, a été retrouvée chez 25 patients soit 36%. Presque la moitié des patients (48.5%) avaient une hyperuricémie. Quatre patients ont développé un diabète après TR soit 6% des cas. La perte du greffon a été notée chez 12 patients et 2 patients sont décédés dont un avec un greffon fonctionnel. En analyse univariée, l'hyperuricémie et la dyslipidémie ont été considérées comme facteur de risque de perte du greffon et retour en dialyse avec p = 0.024 et 0.021 respectivement. Les complications métaboliques après TR sont fréquentes et méritent une attention particulière car elles représentent un facteur de morbi-mortalité. L’éducation précoce du patient greffé est nécessaire et s'appuie sur une prise en charge multidisciplinaire impliquant les néphrologues, diététiciennes, psychologues et médecins généralistes.

Effect of donor body mass index on the outcome of donation after cardiac death kidneys: how big is too big?

INTRODUCTION

Morbid obesity (MO) has become an epidemic in the United Sates and is associated with adverse effects on health. The purpose of this study was to examine the effects of MO on the short-term outcomes of kidneys transplanted from donation after cardiac death (DCD) donors.

PATIENTS AND METHODS

Using a prospectively collected database, we reviewed 467 kidney transplantations performed at a single center between January 2008 and June 2011 to identify 67 recipients who received transplants from 40 DCD donors. The outcomes of 14 MO DCD donor kidneys were compared with 53 non-MO DCD grafts. MO was defined as a body mass index ≥ 35. Mean patient follow-up was 16 months.

RESULTS

The MO and non-MO DCD donor groups were similar with respect to donor and recipient age, gender, race, cause of death and renal disease, time from withdrawal of life support to organ perfusion, mean human leukocyte antigen (HLA) mismatch, and overall recipient survival. Organs from MO DCD donors also had comparable rates of delayed graft function (21.4% vs 20.0%; P = not significant [NS]). At 1 year post-transplantation, a small but statistically insignificant difference was observed in the graft survival rates of MO and non-MO donors (87% vs. 96%; P = NS). One MO kidney had primary nonfunction.

CONCLUSIONS

These data demonstrate that kidneys procured from MO DCD donors have equivalent short-term outcomes compared with non-MO grafts and should continue to be used. Further investigation is needed to examine the effect of MO on long-term renal allograft survival.

Inhibition of the mTOR pathway: a possible protective role in coronary artery disease

The main approach to obesity and type-II diabetes is to unravel the mechanisms involved in nutrient absorption and fuel allocation. In conditions of over-nutrition, cells must cope with a multitude of extracellular signals generated by changes in nutrient load, hormonal milieu, adverse cytokine/adipokine profile, and apoptosis/anti-apoptosis processes. To date studies have demonstrate that among all nutrients, lipids and carbohydrates play a major regulatory role in the gene transcription of glycolytic and lipogenic enzymes, insulin, and adipokines. These nutrients mainly exert their effects through the gene expression of sterol responsive binding protein 1 and 2 (SREBP) and the mammalian target of rapamycin (mTOR). Excess of adipose tissue is known to confer a significantly higher risk of coronary artery disease. Administration of rapamycin effectively attenuated inflammation, inhibited progression, and enhanced stability of atherosclerotic plaques in animal models. Herein we discuss the mTOR pathway and the molecular mechanisms of mTOR inhibitors, hypothesizing a possible protective role in atherosclerosis, taking into account also previous clinical studies emphasizing their opposite role.

Guideline use: a survey of dietitians working with adult kidney transplant recipients

AIM

  To establish current service provision as well as barriers and enablers to guideline implementation in the Nutritional Management of Adult Kidney Transplant Recipients (KTR).

METHODS

  Fifteen primary renal transplant centres (15/17; 88% response rate) and 21 secondary renal transplant centres (21/24; 88% response rate) responded to an online survey addressing key questions investigating their current practice in the nutritional management of adult KTR.

RESULTS

  Referral from primary to secondary sites was limited with only two sites (9%) routinely receiving referrals. Allocated funding for KTR at secondary sites was low (n = 4, 14%). Many primary sites received nil or <0.5 full-time equivalent (FTE) funding for inpatient (n = 8, 53%); and nil or ≤0.2 FTE funding for outpatient services (n = 9, 60%). In sites reporting FTE hours, the average dietitian-to-patient ratio was 1 FTE dietitian for every 383 (range 50-1280) annually transplanted patients. Major barriers identified in delivering nutrition services at primary sites included time/lack of resources and limitations with systems to identify or track transplant recipients.

CONCLUSION

  Dietitian-to-patient ratios in the management of KTR at primary sites are inconsistent and likely to be inadequate at secondary transplant sites to implement guideline recommendations, especially for weight management. Investigations into the effectiveness of innovative interventions such as groups or telehealth are warranted, which may assist practitioners to achieve guideline recommendations in an environment of limited resources.

Characterizing dietary intake and physical activity affecting weight gain in kidney transplant recipients

CONTEXT

Weight gain after kidney transplantation affects 50% to 90% of kidney transplant recipients. Factors leading to weight gain in recipients are thought to include a change in lifestyle (eg, dietary intake and physical activity), age, race, sex, and immunosuppressant medications.

OBJECTIVE

To examine dietary intake and physical activity of kidney transplant recipients at baseline and 3 and 6 months after transplantation to identify contributing factors to weight gain.

DESIGN

Descriptive, correlational study using secondary data from a larger parent study examining genetic and environmental contributors to weight gain after kidney transplantation.

PARTICIPANTS AND SETTING

Forty-four kidney transplant recipients at a mid-South university hospital-based transplant institute who had dietary intake, physical activity, and clinical data at baseline and 3 and 6 months were included.

MAIN OUTCOME MEASURES

Dietary intake, physical activity, weight, and body mass index.

RESULTS

Mean weight gain increased by 6% from baseline to 6 months. Interestingly, dietary intake did not change significantly from baseline to 6 months. Hours of sleep per day decreased during the same period (P = .02). Dietary intake, physical activity, age, race, sex, and immunosuppression showed no significant relationship to weight gain at 6 months.

CONCLUSION

Little consideration has been given to dietary intake and physical activity of kidney transplant recipients and the effects of these variables on weight gain. Further studies with a larger sample are needed, as weight gain after transplantation is a significant risk factor for diminished long-term outcomes.

Recipient and donor body mass index as important risk factors for delayed kidney graft function

BACKGROUND

Obesity is increasingly impacting the overall health status and the global costs for health care. The increase in body mass index (BMI) is also observed in kidney allograft recipients and deceased organ donors.

METHODS

In a retrospective single-center study, we analyzed 1132 deceased donor kidney grafts, transplanted at our institution between 2000 and 2009 for recipient and donor BMI and its correlation with delayed graft function (DGF). Recipients/donors were classified according to their BMI (<18.5, 18.5-24.9, 25-29.9, and >30 kg/m(2)). DGF was defined as requirement for one dialysis within the first week after transplantation.

RESULTS

Overall DGF rate was 32.4%, mean recipient BMI was 23.64 ± 3.75 kg/m(2), and mean donor BMI was 24.69 ± 3.44 kg/m(2). DGF rate was 25.2%, 29.8%, 40.9%, and 52.6% in recipients with BMI less than 18.5, 18.5 to 24.9, 25 to 29.9, and more than 30 kg/m, respectively (P<0.0001). Donor BMI less than 18.5, 18.5 to 24.9, 25 to 29.9, more than 30 kg/m(2) resulted in a DGF rate of 22.5%, 31.0%, 37.3%, and 51.2% (P < 0.0001). Multivariate analysis revealed recipient BMI and dialysis duration as independent risk factors for DGF. DGF results in inferior 1- and 5-year graft and patient survival.

CONCLUSION

Recipient and donor BMI correlate with the incidence of DGF. Awareness thereof should have an impact on peri- and posttransplant measures in renal transplant recipients.

Exercise training for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a worldwide public health problem. In the National Kidney Foundation Disease Outcomes Quality Initiative guidelines it is stressed that lifestyle issues such as physical activity should be seen as cornerstones of the therapy. The physical fitness in adults with CKD is so reduced that it impinges on ability and capacity to perform activities in everyday life and occupational tasks. An increasing number of studies have been published regarding health effects of various regular exercise programmes in adults with CKD and in renal transplant patients.

OBJECTIVES

We aimed to: 1) assess the effects of regular exercise in adults with CKD and kidney transplant patients; and 2) determine how the exercise programme should be designed (e.g. type, duration, intensity, frequency of exercise) to be able to affect physical fitness and functioning, level of physical activity, cardiovascular dimensions, nutrition, lipids, glucose metabolism, systemic inflammation, muscle morphology and morphometrics, dropout rates, compliance, adverse events and mortality.

SEARCH STRATEGY

We searched the Cochrane Renal Group's specialised register, CENTRAL, MEDLINE, EMBASE, CINAHL, Web of Science, Biosis, Pedro, Amed, AgeLine, PsycINFO and KoreaMed. We also handsearched reference lists of review articles and included studies, conference proceeding's abstracts. There were no language restrictions.Date of last search: May 2010.

SELECTION CRITERIA

We included any randomised controlled trial (RCT) enrolling adults with CKD or kidney transplant recipients undergoing any type of physical exercise intervention undertaken for eight weeks or more. Studies using less than eight weeks exercise, those only recommending an increase in physical activity, and studies in which co-interventions are not applied or given to both groups were excluded.

DATA COLLECTION AND ANALYSIS

Data extraction and assessment of study and data quality were performed independently by the two authors. Continuous outcome data are presented as standardised mean difference (SMD) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

Forty-five studies, randomising 1863 participants were included in this review. Thirty two studies presented data that could be meta-analysed. Types of exercise training included cardiovascular training, mixed cardiovascular and resistance training, resistance-only training and yoga. Some studies used supervised exercise interventions and others used unsupervised interventions. Exercise intensity was classed as 'high' or 'low', duration of individual exercise sessions ranged from 20 minutes/session to 110 minutes/session, and study duration was from two to 18 months. Seventeen per cent of studies were classed as having an overall low risk of bias, 33% as moderate, and 49% as having a high risk of bias.The results shows that regular exercise significantly improved: 1) physical fitness (aerobic capacity, 24 studies, 847 participants: SMD -0.56, 95% CI -0.70 to -0.42; walking capacity, 7 studies, 191 participants: SMD -0.36, 95% CI-0.65 to -0.06); 2) cardiovascular dimensions (resting diastolic blood pressure, 11 studies, 419 participants: MD 2.32 mm Hg, 95% CI 0.59 to 4.05; resting systolic blood pressure, 9 studies, 347 participants: MD 6.08 mm Hg, 95% CI 2.15 to 10.12; heart rate, 11 studies, 229 participants: MD 6 bpm, 95% CI 10 to 2); 3) some nutritional parameters (albumin, 3 studies, 111 participants: MD -2.28 g/L, 95% CI -4.25 to -0.32; pre-albumin, 3 studies, 111 participants: MD - 44.02 mg/L, 95% CI -71.52 to -16.53; energy intake, 4 studies, 97 participants: SMD -0.47, 95% CI -0.88 to -0.05); and 4) health-related quality of life. Results also showed how exercise should be designed in order to optimise the effect. Other outcomes had insufficient evidence.

AUTHORS' CONCLUSIONS

There is evidence for significant beneficial effects of regular exercise on physical fitness, walking capacity, cardiovascular dimensions (e.g. blood pressure and heart rate), health-related quality of life and some nutritional parameters in adults with CKD. Other outcomes had insufficient evidence due to the lack of data from RCTs. The design of the exercise intervention causes difference in effect size and should be considered when prescribing exercise with the aim of affecting a certain outcome. Future RCTs should focus more on the effects of resistance training interventions or mixed cardiovascular- and resistance training as these exercise types have not been studied as much as cardiovascular exercise.

Impact of body mass index on graft loss in normal and overweight patients: retrospective analysis of 206 renal transplants

BACKGROUND

Excess body mass is increasingly prevalent in transplant recipients. Currently, most investigators consider body mass index (BMI) a categorical variable, which assumes that all risk factors and transplant outcomes will be similar in all patients within the same category. We investigated the effect of categorical and continuous BMI increments on renal transplant outcome in normal weight (NW: BMI 18.5-24.9) and overweight (OW: BMI 25-30) patients.

METHODS

We retrospectively studied 206 patients. The mean BMI of our population was 24.3 ± 2.83 kg/m(2) . Patients of each group were similar regarding age, gender, time on dialysis, donor type, cold ischemia time, and number of HLA mismatches. The independent association of BMI with survival was determined using Cox multivariate regression.

RESULTS

OW patients showed a higher prevalence of co-morbidities. In patients with graft loss, there was a higher incidence of delayed graft function, chronic allograft nephropathy, acute rejection, and hypertension. Graft survival was significantly lower in OW patients compared to NW patients upon Kaplan-Meier analysis (p = 0.008). In a multivariate Cox regression analysis, the initial BMI, evaluated as a continuous variable, remained an independent predictor of graft loss (hazard ratio 1.21, 95% CI 1.04-1.47). However, with patient stratification into World Health Organization BMI category and, further, into quartiles of initial BMI, no significant correlation between BMI category and graft loss was found.

CONCLUSION

We suggest that increasing BMI value, although without categorical variation, may represent an independent risk factor for graft loss. Our retrospective analysis of a small sample population will require further studies to confirm these data.

Evaluation of dietetic advice for modification of cardiovascular disease risk factors in renal transplant recipients

OBJECTIVE

To investigate the effect of dietitian involvement in a multidisciplinary lifestyle intervention comparing risk factor modification for cardiovascular disease with standard posttransplant care in renal transplant recipients (RTR) with abnormal glucose tolerance (AGT).

DESIGN

Randomized controlled trial.

SETTING

Hospital outpatient department.

PATIENTS

Adult RTR with AGT.

INTERVENTION

RTR with AGT were randomized to a lifestyle intervention that consisted of either regular consultations with the dietitian and multidisciplinary team or standard care.

MAIN OUTCOME MEASURES

Dietary intake, physical activity (PA) levels, cardiorespiratory fitness (CF), and anthropometry.

RESULTS

Total fat and percent saturated fat intake rates were significantly lower in the intervention group as compared with the control group at 2-year follow-up, 54 g (16 to 105 g) versus 65 g (34 to 118 g), P = .01 and 10% (5% to 17%) versus 13% (4% to 20%), P = .05., respectively. There was a trend for an overweight (but not obese) individual to lose more weight in the intervention group (4% loss vs. a gain of 0.25% at the 2-year follow-up). Overall, RTR were significantly less fit than age- and gender-matched controls, mean peak oxygen uptake was 19.42 ± 7.09 mL/kg per minute versus 28.35 ± 8.80 mL/kg per minute, P = .000. Simple exercise advice was not associated with any improvement in total PA or CF in either group at the 2-year follow-up.

CONCLUSION

Dietary advice can contribute to healthier eating habits and a trend for weight loss in RTR with AGT. These improvements in conjunction with multidisciplinary care and pharmacological treatment can lead to improvements in cardiovascular risk factors such as lipid profile. Simple advice to increase PA was not effective in improving CF and other measures are needed.

Primary care of the renal transplant patient

There has been a remarkable rise in the number of kidney transplant recipients (KTR) in the US over the last decade. Increasing use of potent immunosuppressants, which are also potentially diabetogenic and atherogenic, can result in worsening of pre-existing medical conditions as well as development of post-transplant disease. This, coupled with improving long-term survival, is putting tremendous pressure on transplant centers that were not designed to deliver primary care to KTR. Thus, increasing numbers of KTR will present to their primary care physicians (PCP) post-transplant for routine medical care. Similar to native chronic kidney disease patients, KTRs are vulnerable to cardiovascular disease as well as a host of other problems including bone disease, infections and malignancies. Deaths related to complications of cardiovascular disease and malignancies account for 60-65% of long-term mortality among KTRs. Guidelines from the National Kidney Foundation and the European Best Practice Guidelines Expert Group on the management of hypertension, dyslipidemia, smoking, diabetes and bone disease should be incorporated into the long-term care plan of the KTR to improve outcomes. A number of transplant centers do not supply PCPs with protocols and guidelines, making the task of the PCP more difficult. Despite this, PCPs are expected to continue to provide general preventive medicine, vaccinations and management of chronic medical problems. In this narrative review, we examine the common medical problems seen in KTR from the PCP's perspective. Medical management issues related to immunosuppressive medications are also briefly discussed.

Kidney transplantation: a systematic review of interventional and observational studies of physical activity on intermediate outcomes

Kidney transplant patients have decreased quality and longevity of life. Whether exercise can positively affect associated outcomes such as physical functioning, metabolic syndrome, kidney function, and immune function, has only been addressed in relatively small studies. Thus the aim of this systematic review was to determine effects of physical activity level on these intermediate outcomes in kidney transplant patients. We electronically and hand searched to identify 21 studies (6 retrospective assessments of habitual physical activity and 15 intervention studies including 6 controlled trials). After study quality assessment, intermediate outcomes associated with quality and longevity of life were expressed as correlations or percentage changes in addition to effect sizes. Habitual physical activity level was positively associated with quality of life and aerobic fitness and negatively associated with body fat (medium to large effect sizes). Exercise interventions also showed medium to large positive effects on aerobic capacity (10%-114% increase) and muscle strength (10%-22% increase). However, exercise programs had minimal or contradictory effects on metabolic syndrome and immune and kidney function. In kidney transplant patients, physical activity intervention is warranted to enhance physical functioning. Whether exercise impacts on outcomes associated with longevity of life requires further study.

Depression is an important contributor to low medication adherence in hemodialyzed patients and transplant recipients

End-stage renal disease (ESRD) is a growing public health concern and non-adherence to treatment has been associated with poorer health outcomes in this population. Depression, likely to be the most common psychopathology in such patients, is associated with increased morbidity and mortality. We compared psychological measures and self-reported medication adherence of 94 kidney transplant recipients to those of 65 patients receiving hemodialysis in a major medical center in Brooklyn, New York. Compared to the transplant group, the hemodialysis cohort was significantly more depressed as determined by the Beck Depression Inventory score. They also had a significantly lower adherence to medication as reported on the Medication Therapy Adherence Scale. Using hierarchical multiple regression analysis, the variance in depression was the only statistically significant predictor of medication adherence beyond gender and mode of treatment, accounting for an additional 12% of the variance. Our study strongly suggests that a depressive affect is an important contributor to low medication adherence in patients with ESRD on hemodialysis or kidney transplant recipients.

Serum leptin, insulin resistance, and body fat after renal transplantation

OBJECTIVE

Our objective was to evaluate serum levels of leptin, body mass index (BMI), body-fat percentage (BF%), and insulin resistance in the first year after renal transplantation.

DESIGN

This study involved a prospective, observational cohort.

SETTING

The setting was a transplant unit of a university teaching hospital in Porto Alegre, Brazil.

PATIENTS

Thirty-two patients who underwent renal transplantation were prospectively followed for 1 year. A control group of 19 healthy individuals, matched by sex, age, and BMI, was included in the study.

METHODS

Body mass index and BF% were measured according to anthropometric measures, serum leptin was measured by radioimmunoassay, and the homeostasis model assessment (HOMA) was used as an index of insulin resistance. Anthropometric measures and biochemical markers were evaluated prospectively, starting at transplant time and then every 3 months for up to 1 year.

RESULTS

Leptin levels were increased before transplantation, and decreased significantly in the first year (median, 11.9 [interquartile range, 9.2 to 25.2] to 9.3 [4.9 to 16.4] ng/mL; P < .001). The HOMA values presented a similar pattern, decreasing from 2.4 +/- 1.5 (mean +/- SD) before transplantation, to 1.5 +/- 1.1 (P = .001) at 3 months after transplantation, but increasing to 2.0 +/- 1.7 at month 12 after transplantation (P = not significant). The BMI and BF% increased significantly in the first year after transplantation (23.3 +/- 2.7 kg/m(2) vs. 24.4 +/- 2.7 kg/m(2), P = .001, and 23.71% +/- 7.79% vs. 25.63% +/- 7.68%, P = .002, respectively). According to multivariate regression analysis, HOMA levels and BF% independently predicted leptin levels after transplantation.

CONCLUSIONS

We found that leptin serum levels decreased significantly over the first posttransplant year. However, the effect of transplantation on insulin resistance appears to be transitory, and BF% also increases steadily in this period. The beneficial profile of leptin levels is counterbalanced by the detrimental effects of insulin resistance and BF% that may be related to the elevated cardiovascular risk observed after transplantation.

Obesity management in adults with CKD

A 22-year-old African-American woman who has been dialysis dependent for four months due to hypertensive kidney disease is referred for kidney transplantation evaluation. Due to the recent occlusion of her left forearm arteriovenous graft, she is currently being dialyzed via a right internal jugular tunneled catheter. Her medications include methyldopa 250 mg bid, Tums 1000 mg with each meal and erythropoietin with dialysis. The patient is single without children, unemployed and lives with her 38 year old mother. She does not smoke or drink. Her review of systems is unremarkable. On physical exam, her weight is 284 pounds, height is 5 feet 2 inches and her body mass index is 51.9 kg/m2. The blood pressure is 130/80 and the cardiac and pulmonary exams are unremarkable. The surgeon feels she is otherwise a good candidate for transplantation except she must lose weight before being listed. What advice should she be given regarding weight loss?

Risk factors and consequences of delayed graft function in deceased donor renal transplant patients receiving antithymocyte globulin induction

BACKGROUND

Induction rabbit antithymocyte globulin (rATG) is largely used in renal allograft recipients at risk for delayed graft function (DGF) and immunologic rejection. The purpose of our study was to characterize risk factors and outcomes associated with DGF when it occurs in recipients undergoing routine rATG induction.

METHODS

We retrospectively reviewed our experience in a predominantly high-risk population receiving modern immunosuppressive regimens.

RESULTS

Of 231 deceased-donor transplants, high-risk characteristics included African American race (68%), retransplants (12%), peak panel reactive antibody of atleast 20% (19%), expanded criteria donor kidney (15%), and cold ischemia time exceeding 24 hr (27%). DGF occurred in 29% of patients. rATG was continued to a dose of 7.3 mg/kg in DGF patients and 5 mg/kg in non-DGF patients (P<0.0001). Risk factors for DGF were recipient body mass index greater than 30 kg/m(2) (odds ratio [OR]=1.5, P=0.02), female donor/male recipient pairings (OR=1.5, P=0.033), sirolimus use (OR=1.7, P=0.003), and donor creatinine more than 1.5 mg/dL (OR=1.6, P=0.016). One-year patient survival (99% non-DGF, 91% DGF; P=0.001) and acute rejection incidence through 36 months (11% non-DGF, 22.4% DGF; P=0.025) differed between groups. DGF patients experienced a higher rejection rate during the second and third years posttransplant. Death-censored graft survival was similar throughout 36 months.

CONCLUSION

In kidney transplantation with routine rATG induction, DGF was related to size and gender, donor creatinine, and immunosuppressive protocol. Despite low first-year rejection rates, DGF was associated with inferior patient survival. Importantly, patients with DGF continued to be at risk for rejection beyond the first year. Donor and recipient selection impacts short-term outcomes, and induction alone may not confer a long-term advantage without further modification of baseline therapy.

Laparoscopic gastric banding surgery performed in obese dialysis patients prior to kidney transplantation

Obese patients with end-stage renal disease who receive a kidney transplant experience greater rates of posttransplantation diabetes, delayed graft function, and local wound complications. Many centers exclude obese patients from transplantation programs. Diet, exercise, and medication in general are not reliable weight loss options for patients with end-stage renal disease; hence, bariatric surgery should be considered. We report 3 patients who underwent laparoscopically adjustable gastric banding, which enabled sufficient weight loss to gain eligibility for kidney transplantation. All these patients subsequently underwent successful uncomplicated kidney transplantations.

Asymmetric dimethylarginine and adiponectin after renal transplantation: role of obesity

BACKGROUND

In obese renal transplant recipients, we assessed the course of selected proinflammatory factors liable to influence long-term outcomes of transplant patients and kidney grafts.

METHODS

In a prospective cohort study, we examined a total of 140 renal transplant recipients for a period of 12 months. Based on body mass index (BMI), patients were divided into Group I (BMI > or = 30 kg/m2, 68 patients) and Group II (BMI < or = 30 kg/m2, 72 patients).

RESULTS

Twelve months after renal transplantation, significant differences were found between Group I versus Group II in plasma levels of asymmetric dimethylarginine (ADMA) (3.65 [SD +/- 0.47 micromol/L] versus 2.01 [SD +/- 0.36 micromol/L], P < .01), adiponectin (ADPN) (15.4 [SD +/- 6.6 microg/mL] versus 22.3 [SD +/- 8.2 microg/mL], P < .01), leptin (51.3 [SD +/- 11.2 ng/L] versus 21.3 [SD +/- 9.2 ng/L], P < .01), soluble leptin receptor (24.6 [SD +/- 8.4 U/mL] versus 46.1 [SD +/- 11.4 U/mL], P < .01), resistin (20.8 [SD +/- 10.1 microg/mL] versus 14.6 [SD +/- 6.4 microg/mL], P < .025), and triglycerides (3.9 [SD +/- 1.6] versus mmol/L 2.8 [SD +/- 1.6 mmol/L], P < .01). There were significant correlations between ADMA and BMI (r = 0.520; P < .001), and ADPN and BMI (r = -0.570, P < .001). The correlation between ADMA and inulin clearance (Cin) was weak (r = -0.185, P < .05).

CONCLUSIONS

Obesity after renal transplantation is associated with increased ADMA and decreased ADPN in plasma, and this may represent a risk factor for renal transplant recipients.

Management of cardiovascular disease in renal transplant recipients

Cardiovascular disease is a major cause of graft loss and the leading cause of death in renal transplant recipients. Although there are robust data on the frequency of risk factors and their contributions to cardiovascular disease in this population, few trials have demonstrated the benefit of modifying these risk factors to reduce cardiovascular events. Nevertheless, it is widely accepted that the clinical acumen filtered through the best available studies in the general population be used to treat individual renal transplant recipients given their high cardiovascular mortality. Transplant task forces and the Kidney Disease Outcomes Quality Initiative have created guidelines for this purpose. This review examines the data available for prevention and treatment of major risk factors contributing to cardiovascular disease in renal transplant recipients. The contribution of immunosuppressive agents to each risk factor and the evidence to support lifestyle modification as well as drug therapy are examined. Reducing cardiovascular risk factors requires an integrative approach that is best accomplished by a team of health care professionals. It creates a significant challenge but one that must be met if allograft survival is to improve.

Pretransplant obesity: a weighty issue affecting transplant candidacy and outcomes

Because of the global increase in prevalence of obesity, many more overweight and obese individuals are undergoing evaluation for transplantation than in the past. Although obesity seems to provide a survival benefit in dialysis patients, obesity has traditionally been considered a contraindication for transplantation of most organs. It is theorized that obesity will contribute to worse transplant outcomes, including lower rates of graft and patient survival and higher rates of delayed graft function and infection. This review evaluates the available literature evaluating outcomes of obese patients with end-stage organ failure who undergo transplantation. Obesity seems to be associated with increased rates of wound infection after transplantation. However, other adverse transplant outcomes related to obesity seem to be dependent on the type of organ being transplanted and the degree of obesity. For example, a body mass index (BMI) of 30 kg/m(2) may reduce short-term survival in lung transplant recipients; however, obesity does not seem to confer an adverse effect on short- or long-term survival in liver transplant patients until a much higher BMI is reached (such as 35 or 40 kg/m(2)). Each transplant center must determine weight guidelines and criteria for identifying the level of obesity as a contraindication for transplantation. This must be based on organ type, each center's transplant and complication statistics, and available donor pools. Guidelines must also consider the morbidity and mortality risks of the obese patient with organ failure who does not receive a transplant.

Effects of body mass index at transplant on outcomes of kidney transplantation

BACKGROUND

While obesity increases postoperative complications and cardiovascular risks, its effects on long-term kidney transplant outcomes are less clear.

METHODS

We used data from the Australian and New Zealand Dialysis and Transplant (ANZDATA) Registry to examine the relationships between body mass index (BMI, classified according to World Health Organization criteria) at transplant and transplant outcome. Patients starting renal replacement therapy from April 1991 and who received a single-organ, primary kidney transplant (when aged > or =16 years) from April 1991 to December 2004 were included, and followed up to death or December 2005. Survival outcomes adjusted for important covariates were analyzed using Cox models, and cause-specific failures by competing risks analysis. Analysis using BMI at various times posttransplant was also performed. Intermediate outcomes were delayed graft function (DGF) and any acute rejection at 6 months.

RESULTS

In all, 5684 patients were included. Obese patients had worse graft and patient survival only in univariate analyses, not in multivariate analyses (adjusted hazard ratio [HR] for graft loss: 1.10 [0.94-1.259], P=0.25; for patient death: 1.02 [0.83-1.25], P=0.87). Underweight patients had greater late (> or =5 years) death-censored graft loss (adjusted HR: 1.70 [1.10-2.64], P=0.02), mainly due to chronic allograft nephropathy. Obesity was associated with greater odds for DGF (adjusted OR: 1.56 [1.23-1.97], P<0.001) and 6-month risk of acute rejection (adjusted OR: 1.25 [1.01-1.54], P=0.04).

CONCLUSIONS

Obesity per se was not associated with poorer kidney transplant outcomes, although it was associated with factors that led to poorer graft and patient survival. Underweight was associated with late graft failure, mainly due to chronic allograft nephropathy.

Factors Determining Social Participation in the First Year After Kidney Transplantation: A Prospective Study

BACKGROUND

This study describes changes in social participation in the first year after kidney transplantation and examines the influence of clinical factors, health status, transplantation-related symptoms, and psychological characteristics on change in social participation.

METHODS

A prospective study was performed on a cohort of primary kidney transplant recipients, transplanted between March 2002 and March 2003. Data on participation in obligatory activities (i.e., employment, education, household tasks) and leisure activities (i.e., volunteer work, assisting others, sports, clubs/associations, recreation, socializing, going out) were collected by in-home interviews (n=61) at 3 months (T1) and 1 year posttransplantation (T2). Analysis of covariance was performed.

RESULTS

Data showed an increase in participation in obligatory activities and diversity of leisure participation between T1 and T2, although pre-end-stage renal disease level was not regained and differed from the general population. On T1, the majority of employed recipients were on sick leave, but returned to work on T2. Employment rate remained stable. An increase in obligatory participation was predicted by clinical factors (i.e., peritoneal dialysis, initial hospitalization), whereas change in leisure participation was related to serum albumin and cognitive capacity. No effects were found for type of donation, comorbidity, and renal function.

CONCLUSIONS

We found that mainly clinical factors were associated with an increase in participation in society. Although health-status related factors and the psychological attribute self-efficacy may be related to recovery of social participation, their effect was outweighed by the strength of clinical predictors in multivariate analysis.

[Sequelae of organ transplantation]

Transplant medicine has significantly changed the prognosis of diseases leading to terminal organ failure. It has evolved from an experimental procedure to standard therapy for liver, kidney and cardio-vascular diseases. Transplant medicine combines operative organ replacement with the management of severely ill patients before transplantation, as well as life-long follow-up of organ graft recipients. Ten year survival rates of 65% to over 90% have led to a steady increase of transplanted patients seen by general medical care providers which represents a challenge for practicing internists. Apart from organ-specific conditions, infectious, immunosuppressant-associated and metabolic consequences determine long-term survival. These include virus reactivation, graft rejection, anastomotic problems but more importantly general mortality determining factors such as diabetes, renal insufficiency and hypertension, which are often a consequence of immunosuppressant administration. They directly impact long-term survival. The awareness and treatment of these secondary conditions of organ transplantation in routine medical practice contributes significantly to secure the long term success of transplant medicine.

Obesity and adiponectin after kidney transplantation

Obesity and hyperlipidaemia are found very frequently after kidney transplantation (Tx) and may represent independent risk factors for development of atherosclerosis and chronic allograft nephropathy. In a prospective metabolic study, we monitored, a total of 68 obese transplant patients [body mass index (BMI) > 30 kg/m2] with dyslipidaemia over a period of 24 months. We compared the findings of a new therapeutic regimen 1 year (start of the study) and 2 years after renal transplantation. Based on a Subjective Global Assessment Scoring Sheet, we started at the end of the first year with an individualized hypoenergic-hypolipidaemic diet (IHHD). Subsequently, after corticoid withdrawal, IHHD was supplemented regularly with statins (atorvastatin 10-20 mg/day)) and followed-up for 2 years. All patients were on a regimen of cyclosporin A or tacrolimus and mycophenolate mofetil. During the study period, there was a significant decrease in BMI (p < 0.025) and an increase of the adiponectin level (p < 0.01). Long-term therapy was associated with a significant decrease in serum leptin (p < 0.01) and lipid metabolism parameters (p < 0.01). Inulin clearance, mean systolic and diastolic blood pressure, proteinuria, lipoprotein(a) and apo-lipoprotein E isoforms did not differ significantly. Based on our results, we assume that obesity and hyperlipidaemia after renal transplantation can be treated effectively by modified immunosuppression (corticosteroid withdrawal), statins and long-term diet (IHHD). The increased level of adiponectin may be a marker of reducing atherosclerotic and chronic allograft nephropathy processes.

Changes in weight during the first year after kidney transplantation

CONTEXT

Obesity frequently occurs following kidney transplantation and is of concern because of the associated risk for cardiovascular complications.

OBJECTIVE

To examine weight gain over the first year after kidney transplantation to determine associations with gender, ethnicity, and cardiovascular risk factors.

DESIGN

A retrospective analysis was completed on patients who had received transplants between January 1998 and January 2002 and who had matching baseline and 1-year follow-up data and a functional graft.

PARTICIPANTS

The sample consisted of 171 recipients (33% women, 58% African Americans, and 39% whites) with a mean age of 44 +/- 12.2 years.

MAIN OUTCOME MEASURES

Outcome measures included fasting blood sugar, triglycerides, creatinine levels, and body mass index categorized as normal, overweight, or obese.

RESULTS

The total group showed a significant increase in mean weight (6.2 +/- 10.7 kg) and body mass index (2.1 +/- 3.8). Although equivalent at baseline, by 1 year after transplantation there were significantly more obese than normal-weight recipients, regardless of gender or ethnicity, with African Americans increasing more than whites and women more than men. At baseline, those characterized as obese versus normal weight were older (47 vs. 41 years; P < .05), with a higher fasting blood sugar. At 1 year, differences in age and fasting blood sugar disappeared; however, the obese group had higher triglycerides (235 vs. 165, P = .01).

CONCLUSIONS

Weight gain after transplantation was not explained by demographic and clinical factors. We speculate additional variables such as genetic factors influence weight gain and warrant study.