Lynch, Scott

Weight gain or loss is determined by the difference between calorie intake and energy expenditure. The Mifflin metabolic equation most accurately predicts resting energy expenditure (REE) in morbidly obese patients. Hypometabolizers have a measured REE that is much less than predicted and pose the greatest challenge for weight loss induced by restriction of calorie intake. We studied 628 morbidly obese patients (467 female and 161 men, aged 52.5 ± 15.7 years, body mass index [BMI] of 42.6 ± 7.6 m/kg 2 [mean ± SD]). REE was measured using the MedGem® device (REEm) and the percentage variance (δREE%) from the Mifflin-predicted expenditure (REEp) was calculated. Patients with δREE% more than 1 standard deviation from the mean were defined as hypometabolizers (REEm greater than 27% below REEp) and hypermetabolizers (REEm less than 13% above REEp), respectively. Hypometabolizers had greater REEp (1900 ± 301 vs 1719 ± 346 calories, P = 0.005) and lower REEm (1244 ± 278 vs 2161 ± 438 calories, P < 0.0001) than hypermetabolizers. Hypometabolizers, when compared with hypermetabolizers, were taller (167.2 ± 8.4 vs 164.0 ± 10.9 cm, P = 0.04), heavier (123.6 ± 22.2 vs 110.2 ± 23.1 kg, P = 0.006), and had increased BMI (44.1 ± 6.5 vs 40.8 ± 6.5 kg/m 2 , P = 0.04). Other measured anthropometrics were not different between hypo- and hypermetabolizers. Hypometabolizers were less likely to be diabetic (23 vs 43%, P = 0.03) and more likely to be black (25 vs 5%, P = 0.002) than hypermetabolizers. This study defines hypometabolizers as having variance in REEm more than 27 per cent below that predicted by the Mifflin equation. We could not identify any distinguishing phenotypic characteristics of hypometabolizers, suggesting an influence unrelated to body composition.

The objective of this study was to examine whether preoperative recommendation for specific reductions in body mass index (BMI) influenced weight loss in obese surgical patients. We retrospectively reviewed the electronic medical records of 48 patients who enrolled between January 2007 to June 2010 in an 800-calorie per day liquid meal replacement (LMR) weight loss program. Of these, 9 patients (surgical group) enrolled as a result of general surgeon-directed weight loss to enable nonbariatric surgery and 39 enrolled seeking weight loss (medical group). Patients enrolled in the LMR program before bariatric surgery were excluded from analysis. All patients were seen in the setting of a comprehensive weight loss program supervised by a medical bariatrician and followed for a period of 4 months. There were no significant differences in mean initial BMI between surgical and medical patients (41.7 ± 4.55 and 41.6 ± 8.54 kg/m 2 , respectively) or participation time in the weight loss program (120 days vs 133 days). Of the nine surgical patients, only five (56%) reached their weight goal and underwent the planned surgical procedure. Weight loss was significantly less in the surgical compared with medical patients (BMI reduction 4.03 ± 3.99 vs 7.75 ± 4.90 kg/m 2 , respectively; P < 0.05). Weight loss was significantly lower in patients directed to undergo BMI reduction to enable a general surgical procedure. Future studies are needed to assess factors influencing weight loss (metabolism, exercise capacity, motivation) in patients requiring weight loss to enable a surgical procedure.