The procedures that include intestinal bypass (BPD and RYGB) have metabolic effects that act synergistically with weight loss to improve medical comorbidities. The mortality reduction data for these operations are summarized in Tables 2 and Table 3. BPD with or without DS has a reported a mortality of 0.2–8 % at mean follow-up of 2–12 years (Table 2) [36–43]. RYBG had the most data available. The long-term mortality ranged from 1.8 to 9 % at a mean follow-up of 4.4–10 years compared to a control mortality rate of 4.1–28 % during a similar follow-up period (Table 3) [29, 46–51, 54].

Studies that reviewed aggregated mortality of bariatric surgery across multiple procedures are summarized in Table 4. The overall long-term mortality rate for bariatric surgery ranged from 0.68 to 5 % and was significantly lower than control mortality of 6.17–6.3 % at 5–11 years after surgery [57, 58].

Accurate determination of long-term mortality following bariatric surgery can be hindered by several limitations that pervade the current body of literature. First, most of the studies are not case controlled, while randomized trials are even rarer. Many outcome reports do not specifically address long-term mortality as an outcome variable. Also, long-term follow-up is frequently poor in studies of bariatric surgery, such that it is difficult to interpret outcomes in light of diminishing sample sizes. Another inherent issue is the lack of homogeneity of study control groups, which most commonly consist of patients from clinical programs or individuals from the general population. Control groups of patients in clinical programs tend to more closely resemble the comorbidity profiles of surgical patients when contrasted to control groups from the general population. Despite these limitations, the current state of knowledge in bariatric surgery seems to clearly support a reduction in obesity-related mortality in response to bariatric surgery.