We shall address here two famous examples of bariatric surgery results. Although these results seem very much in favor of obesity surgery at first look, they raise interesting questions:
1) The Canadian study (CHRISTOU): This retrospective survey has become classical. It compares two big series of patients, one group has been operated on in a single university hospital between 1986 and 2002 (1035 patients), the other group (control group) has been matched to the first one and included 5746 patients. The key-point is that none of the related diseases that have been recorded in the study was present within two years before inclusion in one of the two groups. On may suppose that counting undesired events after inclusion and/or surgery is a reliable source for evaluating the efficacy of surgery. Actually, the results were impressive: only 7 patients died in the first group (0,7%) 5 years after inclusion, versus 354 (6%) in the second group; 49 (4,7%) versus 1530 (26,7%) had a cardiovascular disease, 21 (2%) versus 487 (8,5%) got cancer, etc. The gaps are huge, which inevitably raises the question: are we dealing with the same patients ? By definition, none of the patients in the control groupe has been a candidate for obesity surgery; the patients who have been candidates were actively involved and likely in a better condition… otherwise how can we explain such a discrepancy as for instance in the rates of cancer? Surgeons have often the feeling that young patients, with fewer associated diseases, are more enthousiast about surgery...
2) The Swedish study (SJOSTROM): The very famous comparative and prospective series of the Swedish Obese Subjects Study has provided highly relevant information. Ten years results have been reported and comparisons have been made between the groups of operated and non operated patients. Quality of life and weight-loss were still better in the operated group. Results in terms of diabetes mellitus were improved as well, but not hypercholesterolemia and hypertension. Although much in favor of the surgical option, this study mitigates the concept of a treatment that would be the ideal cure of all comorbidities.

**CHRISTOU NV, SAMPALIS JS, LIBERMAN M, et al. Surgery decreases long-term mortality, morbidity, and health care use in morbidly obese patients. Annals of Surgery, 2004; 240 : 416-424.
*SJOSTROM L, LINDROOS A-K, PELTONEN M, et al. Lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med, 2004; 351:  2683-2692