Analyses of weight loss after bariatric surgery

Traditionally, bariatric surgery is thought to remove the excess weight from a potentially healthy person, much like a sculptor revealing the statue inside, no matter how big the block of marble is. This thesis demonstrates that this excess weight-loss concept is not supported by evidence. A normal, non-obese body is found to be unrealistic for most bariatric patients, the concept does not explain weight regain or results after revisional surgery and the concept’s percentage excess weight-loss metric, the most commonly used outcome measure in bariatric research, is exposed to lead to false conclusions on outcome of bariatric and metabolic surgery.
The evidence fits a different concept, suggesting that the anatomical and physiological alterations of a bariatric operation merely hinder the flow of calories, with little effect on the underlying factors that drive it. This concept allows weight regain and is consistent with revision surgery results. The percentage alterable weight-loss metric, found in this thesis, is a measure for this hindrance, independent of the baseline body mass index. Novel tools based on this metric are presented for follow-up after bariatric surgery, such as percentile charts, similar to children’s growth charts, that should be preferred to assess weight-loss, weight regain and poor responders above existing methods.
The large deviation in baseline body mass index among bariatric patients and the independently large deviation in postoperative weight-loss found in these charts both support the hypothesis that obesity may not be one type of disease. The BARIA study, introduced in this thesis, will investigate underlying pathways.