Obesity Surgery

, Volume 24, Issue 7, pp 1085–1089 | Cite as

Validating the Alterable Weight Loss (AWL) Metric with 2-Year Weight Loss Outcome of 500 Patients After Gastric Bypass

  • A. W. van de Laar
  • M. H. Dollé
  • L. M. de Brauw
  • S. C. Bruin
  • Y. I. Acherman
Original Contributions



Percentage alterable weight loss (AWL) is the only known weight loss metric independent of the initial body mass index (BMI), a unique feature ideal for use in weight loss research. AWL was not yet validated. The aim of the study is to validate the AWL metric and to confirm advantages over the excess weight loss (EWL) metric.


AWL is tested with 2-year weight loss results of all primary laparoscopic Roux-en-Y gastric bypass patients operated in our hospital. Nadir results of patients with higher and lower initial BMI are compared (Mann–Whitney; p < 0.05) using outcome metrics BMI, percentage weight loss (WL), EWL, and AWL, for the whole group, for each gender, and for <40 and ≥40 years separately.


Five-hundred patients (401 female) out of 508 (98.4 %) had 2-year follow-up. Of all four metrics, only AWL rendered results not significantly influenced by initial BMI. The AWL outcome is initial BMI independent for both genders and age-groups. Results also confirm that women and younger patients had significantly higher AWL outcome.


The recently developed AWL metric, defined as 100% × (initialBMI − BMI) / (initialBMI − 13), is now validated. In contrast to the well-known outcome metrics BMI, EWL, and WL, the AWL metric is independent of the initial BMI. It should replace the misleading EWL metric for comparing weight loss results in bariatric research and for expressing the effectiveness of bariatric procedures. This effectiveness does not act on the total body mass, or on the excess part, but on the alterable part, defined as BMI minus 13 kg/m2 for all adult patients, female, male, young, and old.


Weight loss Gastric bypass Bariatric surgery Biostatistics Body mass index BMI AWL 


Conflict of Interest

The authors Arnold van de Laar, Marije Dollé, Maurits de Brauw, Sjoerd Bruin, and Yair Acherman declare that they have no conflict of interest.


  1. 1.
    Dixon JB, McPhail T, O’Brien PE. Minimal reporting requirements for weight loss: current methods not ideal. Obes Surg. 2005;15(7):1034–9.PubMedCrossRefGoogle Scholar
  2. 2.
    Dallal RM, Quebbemann BB, Hunt LH, et al. Analysis of weight loss after bariatric surgery using mixed-effects linear modeling. Obes Surg. 2009;19:732–7.PubMedCrossRefGoogle Scholar
  3. 3.
    Karmali S, Birch DW, Sharma AM. Is it time to abandon excess weight loss in reporting surgical weight loss? Surg Obes Relat Dis. 2009;4:503–6.CrossRefGoogle Scholar
  4. 4.
    Hatoum IJ, Kaplan LM. Advantages of percent weight loss as a method of reporting weight loss after Roux-en-Y gastric bypass. Obesity. 2013;21(8):1519–25.PubMedCentralPubMedCrossRefGoogle Scholar
  5. 5.
    van de Laar A, de Caluwé L, Dillemans B. Relative outcome measures for bariatric surgery. Evidence against excess weight loss and excess body mass index loss from a series of laparoscopic Roux-en-Y gastric bypass patients. Obes Surg. 2011;21(6):763–7.PubMedCrossRefGoogle Scholar
  6. 6.
    van de Laar A. Bariatric Outcomes Longitudinal Database (BOLD) suggests excess weight loss and excess BMI loss to be inappropriate outcome measures. Demonstrating better alternatives. Obes Surg. 2012;22(12):1843–7.PubMedCrossRefGoogle Scholar
  7. 7.
    van de Laar AW. Algorithm for weight loss after gastric bypass surgery considering body mass index, gender, and age from the Bariatric Outcome Longitudinal Database (BOLD). Surg Obes Relat Dis. 2013 Jun 13. doi:pii: S1550-7289 (13)00181-0. 10.1016/j.soard.2013.05.008. [Epub ahead of print]
  8. 8.
    van de Laar AW, Acherman YI. Weight loss percentile charts of large representative series: a benchmark defining sufficient weight loss challenging current criteria for success of bariatric surgery. Obes Surg. 2013 Nov 14. doi 10.1007/s11695-013-1130-9 [Epub ahead of print]
  9. 9.
    Rosling AM, Sparén P, Norring C, et al. Mortality of eating disorders: a follow-up study of treatment in a specialist unit 1974–2000. Int J Eat Disord. 2011;44(4):304–10.PubMedCrossRefGoogle Scholar
  10. 10.
    Collins S. The limit of human adaption to starvation. Nat Med. 1995;1(8):810–4.PubMedCrossRefGoogle Scholar
  11. 11.
    Sjöström L, Narbro K, Sjöström C, et al. Swedish obese subjects study. Effects of bariatric surgery on mortality in Swedish obese subjects. N Engl J Med. 2007;357(8):741–52.PubMedCrossRefGoogle Scholar
  12. 12.
    Christou N, Efthimiou E. Five-year outcomes of laparoscopic adjustable gastric banding and laparoscopic Roux-en-Y gastric bypass in a comprehensive bariatric surgery program in Canada. Can J Surg. 2009;52:249–58.Google Scholar
  13. 13.
    Deitel M, Gawdat K, Melissas J. Reporting weight loss 2007. Obes Surg. 2007;14:565–8.CrossRefGoogle Scholar
  14. 14.
    Mason EE, Amaral J, Cowan GS, et al. Standards for reporting results. Obes Surg. 1994;4(1):56–65.PubMedCrossRefGoogle Scholar
  15. 15.
    Buchwald H, Estok R, Fahrbach K, et al. Weight and type 2 diabetes after bariatric surgery: systematic review and meta-analysis. Am J Med. 2009;122(3):248–56.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • A. W. van de Laar
    • 1
  • M. H. Dollé
    • 1
  • L. M. de Brauw
    • 1
  • S. C. Bruin
    • 1
  • Y. I. Acherman
    • 1
  1. 1.Department Bariatric SurgerySlotervaartziekenhuisAmsterdamNetherlands

Personalised recommendations