Preservation of energy expenditure after ~20% weight loss in morbidly obese subjects undergoing bariatric surgery — ASN Events
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Preservation of energy expenditure after ~20% weight loss in morbidly obese subjects undergoing bariatric surgery (#47)

Charmaine Tam 1 2 , Georgia Rigas 3 , Tania Matisan 3 , Michael Talbot 3
  1. Charles Perkins Centre and School of Biological Sciences, The University of Sydney, Sydney, NSW, Australia
  2. The Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, NSW, Australia
  3. Department of Surgery, St George Hospital Upper GI Unit, Kogarah, NSW, Australia

Weight loss often results in ‘metabolic adaptation’ or a greater than expected decrease in energy expenditure. However, the effects of different bariatric surgery procedures on energy expenditure are unknown. We compared the effects of ~20% weight loss induced by Roux-en-Y bypass (RYGB), sleeve gastrectomy (SG) or gastric band (Band) on resting metabolic rate (RMR).

Twenty-eight morbidly obese subjects (BMI=40.3±6.7kg/m2; Age=46.2±11.6y) underwent RYGB (n=9; 6 females), SG (n=11; 9 females) or Band (n=8; 7 females). RMR (MedGem, Microlife) and fat-free mass (Impedimed, HydexDF50) were measured at baseline and after ~20% weight loss. Metabolic adaptation was calculated as the difference between the measured RMR and the RMR predicted from body composition, age and sex on the basis of equations established at baseline.

Subjects in the RYGB, SG and Band groups lost 17.8±3.9, 17.4±5.2 and 17.5±6.0% of their body weight by 14±3, 14±3 and 64±19 weeks after surgery, respectively. Losses in fat-free mass comprised 24.0±3.9 (RYGB), 27.6±12.1 (SG) and 25.6±5.8% (Band) of body weight loss and was not different between groups (P=0.79). After equivalent weight loss, measured RMR were similar to predicted RMR levels in all three surgery groups (RYGB= -23±205; SG= -11±194; Band= -82±124kcal), with no significant group difference (P=0.81).

Our findings indicate that energy expenditure levels are remarkably preserved after bariatric surgery with no evidence of metabolic adaptation. Such findings are in contrast to studies of non-surgical treatments for weight loss (1;2), where ‘metabolic adaptation’, a greater than expected drop in energy expenditure occurs. The defence of metabolism associated with bariatric surgery may partially explain its long-term success in the maintenance of weight loss.

  1. Johannsen DL, Knuth ND, Huizenga R, Rood JC, Ravussin E, Hall KD. Metabolic slowing with massive weight loss despite preservation of fat-free mass. J Clin Endocrinol Metab 2012 Jul;97(7):2489-96.
  2. Leibel RL, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med 1995 Mar 9;332(10):621-8.