Effect of Employment Status on Physical Activity and Sedentary Behavior Long-Term Post-Bariatric Surgery.

INTRODUCTION: Inactivity and weight regain are serious problems post-bariatric surgery. Nearly half of waking time is spent at work, representing an opportunity to accumulate physical activity and help avoid weight regain. PURPOSE: The purpose of this study is to evaluate potential differences in physical activity and sedentary time by employment status post-bariatric surgery. METHODS: A total of 48 adults (employed (n = 19), unemployed (n = 29)) aged 50.7 ± 9.4 years, BMI = 34.4 ± 10.1 kg/m2, and 10 ± 3 years post-surgery participated. ActivPAL accelerometers measured transitions, steps, and sedentary time for 7 days. RESULTS: Participants worked on average 8.7 ± 1.8 h/day. Twenty-one percent of employed met step/day guidelines on work-days compared to 10% of unemployed. Employed persons transitioned from sitting-to-standing more on work-days (58.6 ± 17.8) than unemployed (45.0 ± 15.4). Employment status did not influence activity or sedentarism on weekend/non-working-days. CONCLUSION: Employment status may be associated with meaningful improvements in activity post-bariatric surgery.

Effects of Neighborhood Walkability on Physical Activity and Sedentary Behavior Long-Term Post-Bariatric Surgery.

ᅟ: Chronic inactivity and weight regain are serious health concerns following bariatric surgery. Neighborhood walkability is associated with higher physical activity and lower obesity rates in normal weight populations. PURPOSE: Explore the influence of neighborhood walkability on physical activity and sedentarism among long-term post-bariatric surgery patients. METHODS: Fifty-eight adults aged 50.5 ± 9.1 years, with a BMI of 34.6 ± 9.7 kg/m2 having undergone surgery 9.8 ± 3.15 years earlier participated in this study. Participants were asked to wear an ActivPAL™ tri-axial accelerometer attached to their mid-thigh for 7-consecutive days, 24 hours/day. The sample was separated into those that live in Car-Dependent (n = 23), Somewhat Walkable (n = 14), Very Walkable (n = 16), and Walker's Paradise (n = 5) neighborhoods as defined using Walk Score®. ANCOVA was performed comparing Walk Score® categories on steps and sedentary time controlling for age and sex. RESULTS: Neighborhood walkability did not influence either daily steps (F (3, 54) = 0.921, p = 0.437) or sedentary time (F (3, 54) = 0.465, p = 0.708), Car-Dependent (6359 ± 2712 steps, 9.54 ± 2.46 hrs), Somewhat Walkable (6563 ± 2989 steps, 9.07 ± 2.70 hrs), Very Walkable (5261 ± 2255 steps, 9.97 ± 2.06 hrs), and Walker's Paradise (6901 ± 1877 steps, 10.14 ± 0.815 hrs). CONCLUSION: Walkability does not appear to affect sedentary time or physical activity long-term post-surgery. As the built-environment does not seem to influence activity, sedentarism, or obesity as it does with a normal weight population, work needs to be done to tailor physical activity programming after bariatric surgery.

Opioid-receptor antagonism increases pain and decreases pleasure in obese and non-obese individuals.

RATIONALE: Endogenous opioids inhibit nociceptive processing and promote the experience of pleasure. It has been proposed that pain and pleasure lie at opposite ends of an affective spectrum, but the relationship between pain and pleasure and the role of opioids in mediating this relationship has not been tested. OBJECTIVES: Here, we used obese individuals as a model of a dysfunctional opioid system to assess the role of the endogenous opioid peptide, beta-endorphin, on pain and pleasure sensitivity. METHODS: Obese (10M/10F) and age- and gender-matched non-obese (10M/10F) controls were included in the study. Pain sensitivity using threshold, tolerance, and subjective rating assessments and perceived sweet pleasantness using sucrose solutions were assessed in two testing sessions with placebo or the opioid antagonist, naltrexone (0.7 mg/kg body weight). Beta-endorphin levels were assessed in both sessions. RESULTS AND CONCLUSIONS: Despite having higher levels of baseline beta-endorphin and altered beta-endorphin-reactivity to naltrexone, obese individuals reported a similar increase in pain and decrease in pleasantness following naltrexone compared to non-obese individuals. Beta-endorphin levels did not correlate with pain or pleasantness in either group, but naltrexone-induced changes in pain and pleasantness were mildly correlated. Moreover, naltrexone-induced changes in pain were related to depression scores, while naltrexone-induced changes in sweet pleasantness were related to anxiety scores, indicating that pain and pleasantness are related, but influenced by different processes.

Long-term incidence of symptomatic urolithiasis post-bariatric surgery.

INTRODUCTION: The risk of urolithiasis post-Roux-en-Y gastric bypass (RYGB) surgery is higher when compared to the general population. Calcium and vitamin D supplementation is routinely prescribed to these patients, yet compliance with these supplements is unknown. The aim of this study was to assess the incidence of symptomatic de novo urolithiasis post-RYGB and compliance with calcium and vitamin D supplementation. METHODS: A standardized telephone questionnaire was administered to patients who underwent RYGB between 1996 and 2011. Personal and medical histories were obtained with emphasis on episodes of symptomatic urolithiasis and calcium and vitamin D supplementation. RESULTS: The response rate was 48% with 478 patients completing the telephone questionnaire. After a mean follow-up of 7.0 years (range: 1-15), the incidence of post-RYGB symptomatic urolithiasis was 7.3%, while the rate of de novo symptomatic urolithiasis was 5%. The overall median time to present with symptomatic urolithiasis was 3.1 years, with 3.3 years for de novo stone-formers, and 2.0 years for recurrent stone-formers (p = 0.38). In de novo stone-formers, 33% presented with symptomatic urolithiasis 4 to 14 years postoperatively. Compliance with calcium and vitamin D supplementation was 56% and 51%, respectively. CONCLUSIONS: Despite recall bias and lack of confirmatory imaging studies, a high postoperative incidence of symptomatic urolithiasis was found in a large sample of post-RYGB patients. A third of patients with de novo stones, presented with symptomatic urolithiasis 4 to 14 years postoperatively. Compliance with postoperative calcium and vitamin D supplementation was poor and needs improvement.

Keeping the weight off: physical activity, sitting time, and weight loss maintenance in bariatric surgery patients 2 to 16 years postsurgery.

BACKGROUND: Bariatric surgery patients often exhibit low levels of physical activity (PA), despite the presumed importance of PA as an adjunct to surgery for successful weight loss. Little is known regarding the associations of PA and sedentary behaviors to weight loss outcomes in the long term following surgery. The objective of the study was to assess the associations of PA and sitting time with weight status, weight loss, and weight maintenance outcomes in bariatric patients 2-16 years postsurgery. METHODS: A total of 303 Roux-en-Y Gastric Bypass patients (73% female; mean age 47 ± 10 years, mean 7 ± 4 years since surgery) completed a telephone questionnaire. Patients reported moderate-to-vigorous PA (MVPA: # sessions/week ≥30 min) and average daily sitting time (h/day). Associations with various weight outcomes were assessed. RESULTS: Only 48% of patients reported ≥1 session/week MVPA, and mean reported sitting time was 7 ± 4 h/day. Neither MVPA nor sitting time was associated with weight loss outcomes at patients' lowest weight postsurgery. However, both MVPA and sitting time were independently positively and inversely, respectively, associated with total (kg) weight loss, % weight loss, and % excess weight loss at current weight, as well as weight loss maintained vs. regained, controlling for age, sex, surgery type, presurgery BMI, total initial weight loss, and time since surgery. CONCLUSIONS: Results demonstrate associations between MVPA and high sitting time and weight loss outcomes among bariatric patients in the long term. The implications for long-term weight management and concomitant health outcomes highlight the need for appropriate follow-up and interventions in this unique high-risk patient population.

Precision of the iDXA for visceral adipose tissue measurement in severely obese patients.

UNLABELLED: A new measurement tool, the automated software CoreScan, for the GE Lunar iDXA, has been validated for measuring visceral adipose tissue (VAT) against computed tomography in normal-weight populations. However, no study has evaluated the precision of CoreScan in measuring VAT among severely obese patients. PURPOSE: The purpose of the study was to evaluate the precision of CoreScan for VAT measurements in severely obese adults (body mass index > 40 kg·m(-2)). METHODS: A total of 55 obese participants with a mean age of 46 ± 11 yr, body mass index of 49 ± 6 kg·m(-2), and body mass of 137.3 ± 21.3 kg took part in this study. Two consecutive iDXA scans with repositioning of the total body were conducted for each participant. The coefficient of variation, the root-mean-square averages of SD of repeated measurements, the corresponding 95% least significant change, and intraclass correlations were calculated. RESULTS: Precision error was 8.77% (percent coefficient of variation), with a root-mean-square SD of 0.294 kg and an intraclass correlation of 0.96. Bland-Altman plots demonstrated a mean precision bias of -0.08 ± 0.41 kg, giving a coefficient of repeatability of 0.82 kg and a bias range of -0.890 to 0.725 kg. CONCLUSIONS: When interpreting VAT results with the iDXA in severely obese populations, clinicians should be aware of the precision error for this important clinical parameter.

In vivo precision of the GE lunar iDXA for the assessment of lumbar spine, total hip, femoral neck, and total body bone mineral density in severely obese patients.

No study has evaluated the precision of the GE Lunar iDXATM (GE Healthcare) in measuring bone mineral density (BMD) among severely obese patients. The purpose of the study was to evaluate the precision of the GE Lunar iDXATM for assessing BMD, including the lumbar spine L1-L4, L2-L4, the total hip, femoral neck, and total body in a severely obese population (body mass index [BMI]>40 kg/m(2)). Sixty-four severely obese participants with a mean age of 46 ± 11 yr, BMI of 49 ± 6 kg/m(2), and a mean body mass of 136.8 ± 20.4 kg took part in this investigation. Two consecutive iDXA scans (with repositioning) of the total body (total body BMD [TBBMD]), lumbar spine (L1-L4 and L2-L4), total hip (total hip BMD [THBMD]), and femoral neck (femoral neck BMD [FNBMD]) were conducted for each participant. The coefficient of variation (CV), the root mean square (RMS) averages of standard deviations of repeated measurements, the corresponding 95% least significant change, and intraclass correlations (ICCs) were calculated. In addition, analysis of bias and coefficients of repeatability were calculated. The results showed a high level of precision for total body (TBBMD), lumbar spine (L1-L4), and total hip (THBMD) with values of RMS: 0.013, 0.014, and 0.011 g/cm(2); CV: 0.97%, 1.05%, and 0.99%, respectively. Precision error for the femoral neck was 2.34% (RMS: 0.025 g/cm(2)) but still represented high reproducibility. ICCs in all dual-energy X-ray absorptiometry measurements were 0.99 with FNBMD having the lowest at 0.98. Coefficients of repeatability for THBMD, FNBMD, L1-L4, L2-L4, and TBBMD were 0.0312, 0.0688, 0.0383, 0.0493, and 0.0312 g/cm(2), respectively. The Lunar iDXA demonstrated excellent precision for BMD measurements and is the first study to assess reproducibility of the GE Lunar iDXA with severely obese adults.

Safety of laparoscopic vs open bariatric surgery: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review and meta-analysis evaluating the risk of reoperation, wound infection, incisional hernia, anastomotic leak, and all-cause mortality associated with laparoscopic vs open bariatric surgery at a minimum of 12 months' follow-up. DATA SOURCES: We systematically searched the Cochrane Library, EMBASE, and MEDLINE databases through June 1, 2010, for randomized controlled trials comparing laparoscopic with open bariatric surgery. STUDY SELECTION: We included all randomized controlled trials that reported weight loss outcomes and complications at a minimum of 12 months' follow-up and had a minimum of 50 patients. We identified 6 randomized controlled trials, which randomized 510 patients. DATA EXTRACTION: Data were extracted by 2 reviewers on study design, baseline characteristics, and surgical procedure. The outcome data extracted included change in weight and body mass index and the incidence of reoperation, wound infection, incisional hernia, anastomotic leak, and all-cause mortality. DATA SYNTHESIS: We used random-effects models, which accounted for within-study and between-study variability, to estimate pooled risk ratios (95% CIs). Compared with open surgery, laparoscopic surgery was associated with lower risk of wound infection (relative risk [RR], 0.21; 95% CI, 0.07-0.65) and incisional hernia (RR, 0.11; 95% CI, 0.03-0.35). The risk of reoperation (RR, 1.06; 95% CI, 0.70-1.61), anastomotic leak (RR, 0.64; 95% CI, 0.14-2.95), and all-cause mortality (RR, 0.86; 95% CI, 0.22-3.28) may be similar for laparoscopic and open bariatric surgery. CONCLUSION: Laparoscopic surgery may be a safer treatment than open surgery for patients requiring bariatric surgery.

Fibrin sealant associated with increased body temperature and leukocytosis after laparoscopic gastric bypass.

BACKGROUND: Fibrin sealants (FSs) have been used in both open and laparoscopic bariatric surgery to decrease the anastomotic leak rate; however, conclusive evidence to recommend routine use is still lacking. We studied FS use and its effect on the clinical inflammatory response after laparoscopic Roux-en-Y gastric bypass. METHODS: Of 474 consecutive patients scheduled to undergo laparoscopic Roux-en-Y gastric bypass, 158 were assigned to group 1 (no FS used), 158 were assigned to group 2 (FS used at the gastrojejunal anastomosis and gastric staple line), and 158 patients were assigned to group 3 (reverting back to no FS use). RESULTS: The mean age of all patients was 40.7 years (range 18-64), and the mean body mass index was 51.9 kg/m(2) (range 36.7-107). The FS group had a statistically significant higher pulse rate (P = .001), recorded temperature (P = .001), and white blood cell count (P = .001) in the first 48 hours after surgery. The overall leak rate was 4.2% (20 of 474 cases). The mortality rate was 0% in all 3 groups. FS use had no effect on the anastomosis or staple line leak rate. An evaluation for fever of unknown origin was required in 6 patients in the FS group with no evidence of leak. Of these 6 patients, 4 had no evidence of leak on upper gastrointestinal series or computed tomography and 2 underwent surgical exploration with a subphrenic collection found but no evidence of leak intraoperatively (negative findings for pneumatic and methylene blue tests). CONCLUSION: FS use in laparoscopic Roux-en-Y gastric bypass is associated with an increased clinical inflammatory response mimicking anastomotic leak. FS had no effect on the anastomotic leak rate.

Bariatric surgery waiting times in Canada.

BACKGROUND: Severe obesity is reaching epidemic proportions throughout the world, including Canada. The only permanent treatment of severe or morbid obesity is bariatric surgery. Access to bariatric surgery is very limited in Canada. We sought to collect accurate data on waiting times for the procedure. METHODS: We carried out a survey of members of the Canadian Association of Bariatric Physicians and Surgeons and performed a more detailed analysis within Quebec and at one Canadian bariatric surgery centre where a prospectively collected bariatric surgery registry has been maintained since 1983. RESULTS: The survey response rate was 85%. All centres determined whether patients were eligible for bariatric surgery based on the National Institutes of Health criteria. Patients entered the queue as "office contacts" and moved through the queue, with the exit point being completion of the procedure. In 2007, a total of 6783 patients were waiting for bariatric surgery and 1313 procedures were performed in Canada. Assuming these trends are maintained, the calculated average waiting time for bariatric surgery in Canada is just over 5 years (6783/1313). The Fraser Institute and the Wait Times Alliance benchmarks for reasonable surgical waiting times vary from 8 weeks for cancer surgery to 18 months for cosmetic surgery. At one Canadian centre, 12 patients died while waiting for bariatric surgery. CONCLUSION: The waiting times for bariatric surgery are the longest of any surgically treated condition. Given the significant reduction in the relative risk of death with bariatric surgery (40%-89% depending on the study), the current waiting times for the procedure in Canada are unacceptable.

Impact of obesity and bariatric surgery on survival.

Bariatric surgery is the only reliable treatment that offers sustained, long-term weight loss. This results in cure or improvement in almost all of the obesity-associated diseases and translates into reduction in the relative risk of death or increased longevity of the operated morbidly obese population. Since the treatment of obesity-associated conditions is very costly, bariatric surgery also results in significant reductions in healthcare costs with a return on investment of 3 years. It is not just weight loss, it is health gain.

L-selectin shedding in sepsis limits leukocyte mediated microvascular injury at remote sites.

BACKGROUND: Increased soluble L-selectin levels have been shown to attenuate local inflammation-mediated microvascular leakage, and failure to generate high levels has been associated with increased risk of acute respiratory distress syndrome in septic patients. We hypothesized that failure to shed L-selectin in systemic inflammation would result in increased local inflammation-induced leukocyte adherence and microvascular leakage. METHODS: Using intraperitoneal lipopolysaccharide (LPS) or control bicarbonate buffered saline (BBS) and intrascrotal TNFalpha or BBS, mice were randomized to systemic inflammation (LPSip + BBSis), local inflammation (BBSip + TNFis), both (LPSip + TNFis), or control (BBSip+BBSis). Furthermore, mice received intraperitoneal L-selectin Sheddase inhibitor (Ro31-9790) or control vector. With intravital microscopy on cremaster muscle, we measured leukocyte-endothelial cell interactions and microvascular leakage (permeability index). Surface L-selectin was measured by flow cytometry (MCF). RESULTS: Without Ro31-9790, systemic inflammation attenuated increases induced by local inflammation in leukocyte adherence and vascular leakage. Ro31-9790 significantly increased adherence and leakage in systemic and systemic + local inflammation. L-selectin was shed progressively by increasing degrees of inflammation. Ro31-9790 limited this shedding of L-selectin. CONCLUSION: In systemic inflammation, L-selectin shedding is required to limit local inflammation-mediated leukocyte adherence and microvascular leakage. Failure to shed L-selectin may increase leukocyte-mediated end-organ injury in septic patients.

Bariatric surgery reduces cancer risk in morbidly obese patients.

BACKGROUND: To assess the effect of bariatric surgery on the cancer risk of patients with morbid obesity because evidence is mounting of an association between obesity and cancer. METHODS: We performed an observational 2-cohort study. The treatment cohort (n = 1035) included patients who had undergone bariatric surgery from 1986 to 2002. The control group (n = 5746) included age- and gender-matched morbidly obese patients who had not undergone weight-reduction surgery and who were identified from a single-payor administrative database. The subjects with physician or hospital visits for a cancer-related diagnosis or treatment within the 6 months previous to the beginning of the study were excluded. The cohorts were followed up for a maximum of 5 years from study inception. RESULTS: Bariatric surgery resulted in a significant reduction in the mean percentage of excess weight loss (67.1%, P <.001). The surgery patients had significantly fewer physician/hospital visits for all cancer diagnoses (n = 21, 2.0%) compared with the controls (n = 487, 8.45%; relative risk .22, 95% confidence interval .143-.347; P = .001). The physician/hospital visits for common cancers such as breast cancer were significantly reduced in the surgery group (P = .001). For all other cancers, the physician/hospital visits showed a trend toward being lower in the surgery group. Because of the low frequencies, statistical significance could not be demonstrated for individual cancer diagnoses. CONCLUSION: The data suggest that bariatric surgery improves the cancer outcomes in some morbidly obese patients.

Preoperative gender differences in pulmonary gas exchange in morbidly obese subjects.

BACKGROUND: Morbidly obese men may have poorer pulmonary gas exchange compared to morbidly obese women (see Zavorsky et al., Chest 131:362-367, 2007). The purpose was to compare pulmonary gas exchange in morbidly obese men and women at rest and throughout exercise. METHODS: Twenty-five women (age=38+/-10 years, 164+/-7 cm, body mass index or BMI = 51+/-7 kg/m(2), peak oxygen consumption or VO(2peak)=2.0+/-0.4 l/min) and 17 men (age=43+/-9 years, 178+/-7 cm, BMI=50+/-10 kg/m(2), VO(2peak)=2.6+/-0.8 l/min) were recruited to perform a graded exercise test on a cycle ergometer with temperature-corrected arterial blood-gas samples taken at rest and every minute of exercise, including peak exercise. RESULTS: At rest, women were 98% predicted for pulmonary diffusion compared to 88% predicted in men. At rest, women had better pulmonary gas exchange compared to the men which was related to women having a lower waist-to-hip ratio (WHR; p<0.01). Only 20% of the subjects had an excessive alveolar-to-arterial oxygen partial pressure difference (>or=25 mmHg) at peak exercise, but 75% of the subjects showed inadequate compensatory hyperventilation at peak exercise (arterial carbon dioxide pressure >35 mmHg), and both were not different between genders. CONCLUSION: At rest, morbidly obese men have poorer pulmonary gas exchange and pulmonary diffusion compared to morbidly obese women. The better gas exchange in women is related to the lower WHR in the women. During exercise, few subjects showed disturbances in pulmonary gas exchange despite demonstrating poor compensatory hyperventilation at peak exercise.

Compensatory exercise hyperventilation is restored in the morbidly obese after bariatric surgery.

BACKGROUND: Morbidly obese individuals may have poor compensatory hyperventilation during exercise. The objective was to examine pulmonary gas exchange and the compensatory hyperventilatory response during exercise pre- and post-weight reduction surgery in obese subjects. METHODS: Fifteen patients (age=39+/-8 years, body mass index=47+/-6 kg/m2), with an excess weight of 69+/-17 kg, were recruited. Pulmonary function at rest was assessed and arterial-blood gases were sampled at rest and all levels of exercise pre- and 10+/-3 weeks postsurgery. RESULTS: There was a loss of excess weight 21+/-6 kg (p<0.01). Waist and hip circumference decreased by 13+/-9 and 8+/-7 cm, respectively (p<0.01). Prior to surgery, there was no compensatory hyperventilation between rest and peak exercise as arterial PCO2 (PaCO2) remained unchanged (37+/-3 mm Hg). However, postsurgery, there was compensatory hyperventilation as PaCO2 decreased to 33+/-2 mm Hg at peak exercise (p<0.01), with no change in peak oxygen consumption (VO2peak in L/min). Multiple linear regression revealed that the restored ventilatory response to exercise was most strongly associated with the reduction in overall fat mass (adjusted r2=0.25; p=0.03). Total weight loss of 21 kg induces adequate compensatory hyperventilation that begins to show at about 50% of VO2peak, resulting in improved gas exchange at moderate to peak exercise intensities. CONCLUSION: Improvement in compensatory hyperventilation is most closely related to loss in overall fat mass.

Alveolar-membrane diffusing capacity improves in the morbidly obese after bariatric surgery.

BACKGROUND: Morbidly obese individuals may have impaired alveolar-membrane diffusing capacity (DmCO). The purpose of this study was to measure pulmonary diffusing capacity for NO (DLNO) as an index of DmCO pre- and postbariatric surgery in the morbidly obese. METHODS: Twenty-one patients [age = 40 +/- 9 years, body mass index (BMI) = 48.5 +/- 7.2 kg/m2] with an excess weight of 72 +/- 17 kg scheduled for bariatric surgery were recruited. Pulmonary function and arterial blood-gases were measured pre- and postsurgery. RESULTS: DmCO was 88 +/- 23% of predicted before surgery (p < 0.05). There was loss in BMI and excess weight of 7.7 +/- 2.0 kg/m2 and 31 +/- 8%, respectively. Because DmCO = DLNO/2.42, the increase in DLNO postsurgery resulted in a normalization of the predicted DmCO to 97 +/- 29% predicted, or an improvement of DLNO by 11 +/- 18 (95% CI = 3.5, 19.1; p = 0.01) milliliters per minute per millimeter of mercury without any improvement in DLCO. The DLNO/DLCO ratio and alveolar volume both increased, respectively (p < 0.05), and pulmonary capillary blood volume to DmCO ratio decreased postsurgery (p < 0.01). Multiple linear regression revealed that the change in DLNO was most strongly associated with changes in alveolar volume and the waist-to-hip ratio (adjusted r2 = 0.76; p < 0.001) and was not related to the reduction in the alveolar-to-arterial PO2 difference. CONCLUSION: Alveolar-membrane diffusion normalizes within 10 weeks after bariatric surgery. This is likely due to the increase in alveolar volume from the reduction in the waist-to-hip ratio.

Poor compensatory hyperventilation in morbidly obese women at peak exercise.

This study was designed to compare differences in pulmonary gas exchange at rest and at peak exercise in two groups of women: (1) physically active, non-obese women and (2) women with morbid obesity. Fourteen morbidly obese women (body mass index or BMI=49+/-7 kg/m2; peak oxygen consumption or VO2 peak=14+/-2 ml/(kg min)) and 14 physically active non-obese women (BMI=22+/-2 kg/m2; VO2 peak=50+/-6 ml/(kg min)) performed an incremental, ramped exercise test to exhaustion on a cycle ergometer. Arterial blood was sampled at rest and at peak exercise. At rest, the alveolar to arterial oxygen partial pressure difference was 3x higher in the obese women (14+/-10 mmHg) compared to non-obese women (5+/-4 mmHg). Arterial carbon dioxide pressure (PaCO2) was identical in both groups at rest (37+/-4 mmHg). Only the non-obese women showed a decrease in PaCO2 rest to peak exercise (-5+/-3 mmHg). The slope between heart rate and VO2 during exercise was higher in the morbidly obese compared to non-obese women indicating that for the same absolute increase in VO2 a larger increase in heart rate is needed, demonstrating poorer cardiac efficiency in obese women. In conclusion, morbidly obese women have poorer exercise capacity, cardiac efficiency, and compensatory hyperventilation at peak exercise, and poorer gas exchange at rest compared to physically active, non-obese women.

Waist-to-hip ratio is associated with pulmonary gas exchange in the morbidly obese.

BACKGROUND: Morbidly obese individuals (ie, body mass index [BMI], > or = 40 kg/m2) may have a pulmonary gas exchange impairment due to the large fat mass surrounding their abdomen. PURPOSES: To examine the effect of the waist-to-hip (W/H) ratio on pulmonary gas exchange in the morbidly obese. METHODS: Twenty-five morbidly obese individuals (mean [+/- SD] age, 39 +/- 10 years; mean BMI, 49 +/- 7 kg/m2; mean body fat, 50 +/- 6%; mean waist circumference, 135 +/- 15 cm; mean W/H ratio, 0.97 +/- 0.11) scheduled for bariatric surgery were recruited. Arterial blood was sampled in duplicate after 5 min of rest sitting upright. RESULTS: The mean PaO2 at rest was 88 +/- 7 mm Hg (range, 72 to 108 mm Hg), the alveolar-arterial oxygen pressure difference (P[A-a]O2) was 19 +/- 9 mm Hg (range, 1 to 37 mm Hg), and the PacO2 was 38 +/- 3 mm Hg (range, 32 to 44 mm Hg). Linear regression showed that 32% and 36%, respectively, of the variance in the P(A-a)O2 and PaO2 were explained by the W/H ratio (p < 0.004 for both). As well, 20% of the variance in PacO2 was explained by the W/H ratio (p = 0.02). Men had larger W/H ratios (p < 0.01) and poorer gas exchange (p = 0.06) compared to women (mean difference: PaO2, -7 mm Hg; P[A-a]O2, 6 mm Hg). CONCLUSION: Morbidly obese men showed a trend to have poorer pulmonary gas exchange compared to morbidly obese women, and a significant part of the blood gas status in these patients is associated with the W/H ratio.