BLOG | Should we analyze differently new technologies in the bariatric field?

Should we analyze differently new technologies in the bariatric field? 

Author: Jerome Dargent 
Bariatric Surgeon and Editor-in-chief for Obésité, Lyon, France 
SCOPE OBESITY European Fellow 

It seems common sense that less aggressive techniques should be implemented in the field of bariatric surgery. Gastric bypass or sleeve gastrectomy, the two most common operations for the time being, are still relatively risky in terms of post-operative complications and side effects, at least in the eyes of most patients who could be candidates to such procedures. 

For the time being, most of the current techniques that fit into the description of "new bariatric technologies" (e.g. upper GI endoscopic procedures) have rather short-term effects, with few data beyond 18 months post-operatively. Results are strongly influenced by external factors, such as follow-up adherence, in a more important way than regular bariatric surgeries. 

Let us ask ourselves this simple question: is there a "normal way" of gaining or losing weight, in other words is there a typical trajectory of weight-gain/weight-loss? And does this trajectory impact final results (or results at a given endpoint)? As a bariatric medical physician or as a surgeon, you would assume that the typical trajectories are well known: the yoyo ascending curve on one hand in the history of weight gain, the rather steep weight-loss curve followed by a slight or important weight-regain in the longer term of a bariatric surgery. Indeed this is what the medical literature tells us. Optionally a pre-operative weight-loss may affect post-operative weight-loss (or not). At closer look, longitudinal assessment of weight loss is more accurate than the cross-sectional analysis that are routinely performed.   

It is uneasy to define accurately a natural history of obesity, or even a typical evolution of weight-cycling after obesity treatment. Recent literature tells us that there is no clear evidence that weight-cycling is detrimental to health provided confounding factors are eliminated (Casazza et al). Moreover, it has been shown that a history of weight cycling does not compromise further weight-loss (Mason et al). Hence, repeated short-term weight loss is not necessarily detrimental as such, provided the safety profile of the weight-loss procedure remains high. 

Instead of focusing solely on the causes of weight gain/loss or weight regain, weight trajectories curves should be analyzed for themselves. Short-term effects may be described under the term micro-trajectories. For instance, 3 month periods are commonly analyzed in the field of new technologies versus 1 year-periods in typical surgical procedures. Regular surgeries experience variations as well, that can be minimized with for instance a multivariate mixed-effects modelling, such as published by Dallal et al. Micro-trajectories cannot be predicted the same way. Should we introduce new methods of evaluation when it comes to minimally invasive techniques? Can we define the causes of atypical trajectories (control effect, center effect, behavorial effects, etc.)?  

The existence of an "on-off" pattern renders weight-loss curve more complex to analyze. Such an effect can be observed in typical surgical procedures as well (e.g. gastric banding, gastric neuro-stimulation). The paradox is that weight-loss may be de-connected from the "on-off" pattern in some cases, when weight-loss continues after a device has ceased to act. We have learned for more than 20 years of lap-banding that you get unexpected trajectories, e.g. weight-loss before or after a "band efficacy-period". Atypical trajectories may be observed more often in minimally invasive methods that achieve less important weight-loss and have a shorter duration of efficacy. 

In conclusion, caution is in order when evaluating the benefits of a given technique, and its safety profile, and when designing the methods of RCT (randomized control trials) in obesity treatment. This has been done for instance by the ASGE (American Society of Gastro Enterology). Eventually, the quest for alternative assessment of obesity treatment meets current preoccupation for new ways of designing trials (Collins et al). Additionally, one must not forget that each procedure has a specific weight loss pattern, i.e. a different "signature". 

References 

1. Casazza K et al. (2013) Myths, presumptions, and facts about obesity. N Engl J Med. 
    
2. Mason C et al (2013) History of weight cycling does not impede future weight loss or metabolic improvements in postmenopausal women. Metabolism. 
    
3. Dallal RM et al (2009) Analysis of weight loss after bariatric using mixed-effects linear modeling. Obes Surg. 
    
4. Collins S et al. Adaptative clinical trial design (2015). New Eng J of Med. 
    

*You will be able to hear Jerome discuss this topic more in depth analyze at ICO 2016 on Tuesday 3rd May,  

His talk is ‘New Techniques in Bariatric Surgery’ and takes place at 10:30-12:30 in Track 4: Novel Insights from Bariatric Surgery. 

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