Maria L. Collazo-Clavell

Accuracy of body mass index in diagnosing obesity in the adult general population.

Background:Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown.Methods:A cross-sectional design of 13 601 subjects (age 20–79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF%). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF%>25% in men and>35% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race.Results:BMI-defined obesity (⩾30 kg m−2) was present in 19.1% of men and 24.7% of women, while BF%-defined obesity was present in 43.9% of men and 52.3% of women. A BMI⩾30 had a high specificity (men=95%, 95% confidence interval (CI), 94–96 and women=99%, 95% CI, 98–100), but a poor sensitivity (men=36%, 95% CI, 35–37 and women=49%, 95% CI, 48–50) to detect BF%-defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF%, while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25–29.9 kg m−2), BMI failed to discriminate between BF% and lean mass in both sexes.Conclusions:The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff of⩾30 kg m−2 has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice for the Perioperative Nutritional, Metabolic, and Nonsurgical Support of the Bariatric Surgery Patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist healthcare professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery medical guidelines for clinical practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist health‐care professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied.

A controlled study of peripheral neuropathy after bariatric surgery

Background: Although peripheral neuropathy (PN) occurs after bariatric surgery (BS), a causal association has not been established. Objectives: To ascertain whether PN occurs more frequently following BS vs another abdominal surgery, to characterize the clinical patterns of PN, to identify risk factors for PN, and to assess if nerve biopsy provides pathophysiologic insight. Methods: Retrospective review identified patients with PN after BS. The frequency of PN was compared with that of an age- and gender-matched, retrospectively evaluated cohort of obese patients undergoing cholecystectomy. Results: Of 435 patients who had BS, 71 (16%) developed PN. Patients developed PN more often after BS than after cholecystectomy (4/126; 3%) (p < 0.001). The clinical patterns of PN were polyneuropathy (n = 27), mononeuropathy (n = 39), and radiculoplexus neuropathy (n = 5). Risk factors included rate and absolute amount of weight loss, prolonged gastrointestinal symptoms, not attending a nutritional clinic after BS, reduced serum albumin and transferrin after BS, postoperative surgical complications requiring hospitalization, and having jejunoileal bypass. Most risk factors were associated with the polyneuropathy group. Sural nerve biopsies showed prominent axonal degeneration and perivascular inflammation. Conclusions: Peripheral neuropathy (PN) occurs more frequently after bariatric surgery (BS) than after another abdominal surgery. The three clinical patterns of PN after BS are sensory-predominant polyneuropathy, mononeuropathy, and radiculoplexus neuropathy. Malnutrition may be the most important risk factor, and patients should attend nutritional clinics. Inflammation and altered immunity may play a role in the pathogenesis, but further study is needed.

Effect of Bariatric Surgery on the Metabolic Syndrome: A Population-Based, Long-term Controlled Study

OBJECTIVE To assess the effect of weight loss by bariatric surgery on the prevalence of the metabolic syndrome (MetS) and to examine predictors of MetS resolution. PATIENTS AND METHODS We performed a population-based, retrospective study of patients evaluated for bariatric surgery between January 1, 1990, and December 31, 2003, who had MetS as defined by the American Heart Association/National Heart, Lung, and Blood Institute (increased triglycerides, low high-density lipoprotein, increased blood pressure, increased fasting glucose, and a measure of obesity). Of these patients, 180 underwent Roux-en-Y gastric bypass, and 157 were assessed in a weight-reduction program but did not undergo surgery. We determined the change in MetS prevalence and used logistic regression models to determine predictors of MetS resolution. Mean follow-up was 3.4 years. RESULTS In the surgical group, all MetS components improved, and medication use decreased. Nonsurgical patients showed improvements in high-density lipoprotein cholesterol levels. After bariatric surgery, the number of patients with MetS decreased from 156 (87%) of 180 patients to 53 (29%); of the 157 nonsurgical patients, MetS prevalence decreased from 133 patients (85%) to 117 (75%). A relative risk reduction of 0.59 (95% confidence interval [CI], 0.48-0.67; P<.001) was observed in patients who underwent bariatric surgery and had MetS at follow-up. The number needed to treat with surgery to resolve 1 case of MetS was 2.1. Results were similar after excluding patients with diabetes or cardiovascular disease or after using diagnostic criteria other than body mass index for MetS. Significant predictors of MetS resolution included a 5% loss in excess weight (odds ratio, 1.26; 95% CI, 1.19-1.34; P<.001) and diabetes mellitus (odds ratio, 0.32; 95% CI, 0.15-0.68; P=.003). CONCLUSION Roux-en-Y gastric bypass induces considerable and persistent improvement in MetS prevalence. Our results suggest that reversibility of MetS depends more on the amount of excess weight lost than on other parameters.

Fat malabsorption and increased intestinal oxalate absorption are common after Roux-en-Y gastric bypass surgery.

BACKGROUND Hyperoxaluria and increased calcium oxalate stone formation occur after Roux-en-Y gastric bypass (RYGB) surgery for morbid obesity. The etiology of this hyperoxaluria is unknown. We hypothesized that after bariatric surgery, intestinal hyperabsorption of oxalate contributes to increases in plasma oxalate and urinary calcium oxalate supersaturation. METHODS We prospectively examined oxalate metabolism in 11 morbidly obese subjects before and 6 and 12 months after RYGB (n = 9) and biliopancreatic diversion-duodenal switch (BPD-DS) (n = 2). We measured 24-hour urinary supersaturations for calcium oxalate, apatite, brushite, uric acid, and sodium urate; fasting plasma oxalate; 72-hour fecal fat; and increases in urine oxalate following an oral oxalate load. RESULTS Six and 12 months after RYGB, plasma oxalate and urine calcium oxalate supersaturation increased significantly compared with similar measurements obtained before surgery (all P ≤ .02). Fecal fat excretion at 6 and 12 months was increased (P = .026 and .055, 0 vs 6 and 12 months). An increase in urine oxalate excretion after an oral dose of oxalate was observed at 6 and 12 months (all P ≤ .02). Therefore, after bariatric surgery, increases in fecal fat excretion, urinary oxalate excretion after an oral oxalate load, plasma oxalate, and urinary calcium oxalate supersaturation values were observed. CONCLUSION Enteric hyperoxaluria is often present in patients after the operations of RYGB and BPD-DS that utilize an element of intestinal malabsorption as a mechanism for weight loss.

Osteomalacia after Roux-en-Y gastric bypass.

OBJECTIVE To emphasize the potential for Roux-en-Y gastric bypass treatment of morbid obesity to result in late development of metabolic bone disease and to illustrate the error of treating a low bone mineral density with bisphosphonates in the presence of unrecognized osteomalacia. METHODS We conducted a retrospective case review of clinical, laboratory, and radiologic details in a patient who underwent Roux-en-Y gastric bypass as well as a review of the literature relative to metabolic bone disease associated with bariatric surgical procedures. RESULTS A 42-year-old woman was diagnosed with high bone turnover osteoporosis and failed to respond to bisphosphonate (alendronate) therapy. Her past medical history included corticosteroid-dependent asthma and a Roux-en-Y gastric bypass surgical procedure for obesity approximately 6 1/2 years before the current assessment. Evaluation revealed vitamin D deficiency in conjunction with pronounced secondary hyperparathyroidism and biochemical evidence of osteomalacia. Aggressive calcium and vitamin D supplementation corrected the vitamin D-deficient state and was accompanied by rapid improvement in clinical symptoms, biochemical variables, and bone mineral density. CONCLUSION This case exemplifies two principles: (1) the potential for a Roux-en-Y gastric bypass surgical procedure to lead to the development of metabolic bone disease and (2) the importance of recognizing mineralization defects as a cause for low bone mineral density, before initiation of therapy with bisphosphonates.

Cardiovascular risk after bariatric surgery for obesity.

Obese patients have an increased prevalence of cardiovascular (CV) risk factors, which improve with bariatric surgery, but whether bariatric surgery reduces long-term CV events remains ill defined. A systematic review of published research was conducted, and CV risk models were applied in a validation cohort previously published. A standardized MEDLINE search using terms associated with obesity, bariatric surgery, and CV risk factors identified 6 test studies. The validation cohort consisted of a population-based, historical cohort of 197 patients who underwent Roux-en-Y gastric bypass and 163 control patients, identified through the Rochester Epidemiology Project. Framingham and Prospective Cardiovascular Munster Heart Study (PROCAM) risk scores were applied to calculate 10-year CV risk. In the validation cohort, absolute 10-year Framingham risk score for CV events was lower at follow-up in the bariatric surgery group (7.0% to 3.5%, p <0.001) compared with controls (7.1% to 6.5%, p = 0.13), with an intergroup absolute difference in risk reduction of 3% (p <0.001). PROCAM risk in the bariatric surgery group decreased from 4.1% to 2.0% (p <0.001), whereas the control group exhibited only a modest decrease (4.4% to 3.8%, p = 0.08). Using mean data from the validation study, the trend and directionality in risk was similar in the Roux-en-Y group. The test studies confirmed the directionality of CV risk, with estimated relative risk reductions for bariatric surgery patients ranging from 18% to 79% using the Framingham risk score compared with 8% to 62% using the PROCAM risk score. In conclusion, bariatric surgery predicts long-term decreases in CV risk in obese patients.

Assessment and Preparation of Patients for Bariatric Surgery

The number of bariatric surgical procedures performed in the United States has increased steadily during the past decade. Currently accepted criteria for consideration of bariatric surgery include a body mass index (calculated as weight in kilograms divided by the square of height in meters) of 40 kg/m2 or greater (or >35 kg/m2 with obesity-related comorbidities), documented or high probability of failure of nonsurgical weight loss treatments, and assurance that the patient is well informed, motivated, and compliant. Appropriate patient selection is important in achieving optimal outcomes after bariatric surgery. In this article, we review our approach to the medical and psychological assessment of patients who want to undergo bariatric surgery. The medical evaluation is designed to identify and optimally treat medical comorbidities that may affect perioperative risks and long-term outcomes. The psychiatric and psychological assessment identifies factors that may influence long-term success in maintaining weight loss and prepares the patient for the lifestyle changes needed both before and after surgery.

Structural and Functional Changes in Left and Right Ventricles After Major Weight Loss Following Bariatric Surgery for Morbid Obesity

Obesity and bariatric surgery have been associated with changes in ventricular function and structure. The aim of the present study was to assess the long-term changes in left ventricular (LV) and right ventricular (RV) function and structure in patients with morbid obesity-body mass index >or=40 kg/m(2) or >or=35 kg/m(2) with co-morbidities-who had lost weight after bariatric surgery compared to nonsurgical controls. We reviewed 57 patients with morbid obesity who had undergone gastric bypass surgery and who had undergone echocardiography before and after surgery. A reference group (n = 57) was frequency matched for body mass index (+/-2 kg/m(2)), gender, age (+/-2 years), and follow-up duration (+/-6 months). After a mean follow-up of 3.6 years, the LV mass and LV mass indexed by height had decreased in the patients who had undergone bariatric surgery and had lost weight. In contrast, these measurements had increased in the patients who had not undergone bariatric surgery. The difference between these 2 groups remained significant after adjusting for potential confounders. At follow-up, neither the patients nor controls showed a significant change in ejection fraction, LV myocardial performance index, or RV myocardial performance index. In the study population as a whole, multivariate analysis showed a positive correlation between the change in body weight and ventricular septum thickness (R = 0.33), posterior wall thickness (R = 0.31), LV mass (R = 0.38), RV end-diastolic area (R = 0.22), and estimated RV systolic pressure (R = 0.39), all with p values <0.05. In conclusion, body weight changes in patients with morbid obesity were associated with changes in LV structure independent of improvement in obesity-related co-morbidities, including obstructive sleep apnea. Weight loss improved the RV end-diastolic area and might prevent progression to RV dysfunction.