In the issue of Annals Surgery, published online on March 6, 2013, Derogar M, Hull MA, Kant P, Ostlund M, Lu Y, and Lagergren J. found the risk of colorectal cancer was significantly increased after bariatric surgery, in a long-term retrospective cohort study In Sweden between 1980 and 2009. Comparing the group of obese patients who had bariatric surgery with another group of obese patients who had no bariatric surgery, the standardized incidence ratio (SIR) of colorectal cancer was 1.60 for the surgical group and 1.26 for the non-surgical group. Meanwhile, the SIR increased with the length of time after surgery and was 2.00 after 10 years or more for the surgical group, while the SIR remained stable over the time for the non-surgical group. 
Gastric bypass surgery has been employed in treating various diseases of the gastrointestinal tract. However, it became the centerpiece of surgical weight loss or so called bariatric surgery about 50 years ago in the US. The idea is to create a state of malabsorption of nutrients by rerouting and shortening the path between the stomach and the end of the small intestine, at the same time, by downsizing the stomach for reducing the volume of each meal. [2, 3]
In promoting the bariatric surgery for those obese patients who want a quick fix, studies have touted its benefits, ranging from immediate, significant improvement in glycemic control among those who had diabetes mellitus, reduced number of cardiovascular deaths and lower incidence of cardiovascular events, to improving the cancer outcomes in some morbidly obese patients. Such an intensive publicity has impressed many people as if the bariatric surgery was the only and best option for weight loss and improvement of general health. [4, 5, 6, 7, 8, 9]
Recent studies including the above-mentioned Annals Surgery article and another article in Obesity Surgery, “Long-term Remission and Relapse of Type 2 Diabetes Mellitus Following Gastric Bypass” should help those obese patients to have second thought before submitting themselves to bariatric surgery. [1, 10]
The surgical re-arrangement of the gastrointestinal tract for weight loss is undoubtedly un-physiological or pathological at least. To facilitate weight loss and maintain a “nearly healthy state”, the post-bariatric patient must strictly follow the postoperative dietary plan for the rest of his life, because many nutritional deficiencies, such as enzymes, minerals and vitamins, and abnormalities, such as dumping syndrome, and indigestion of fibers, resulted with the surgery requires lots of dietary supplements and restrictions. Among the list of restrictions, carbohydrates especially those high in glycemic indices and glycemic loads should be at the top. [11, 12]
An article, Bariatric Surgery: Credits Go To Restricting Carbohydrate Absorption, published on January 20 and 27, 2010, points out that the success in weight loss with gastric bypass surgery or bariatric surgery lies on restricting carbohydrate surgically by reducing the time and the passage of the ileum. Depending on the circumstance in postoperative dieting, there is a possibility of having too many unabsorbed carbohydrates moving into the colon and rectum. The relationship between moving too many unabsorbed carbohydrates into the colon and rectum, and the risk of colorectal cancer has yet to be elucidated. However, studies have positively linked carbohydrate-rich diet and postprandial hyperglycemia to the risk of colorectal cancer. In addition, postprandial hyperglycemia is cited as the cause of inflammation, which results in diabetes mellitus, hypertension, arteriosclerosis and atherosclerosis, cancer, neurodegenerative disorders, and many more. Thus, without restriction on carbohydrates, bariatric surgery can never help prevent and/or reverse diseases. 
Many have successfully lost weight, prevented and/or reversed diseases by restricting carbohydrates alone, without having to risk themselves with the operative and postoperative complications of bariatric surgery. Yet, the individuals with bariatric surgery still need to restrict carbohydrates postoperatively for better health, like those who did not have bariatric surgery but solely adopted carbohydrate-restricted diet, how can one tout that bariatric surgery is the only and best option for losing weight and maintaining a healthy life?
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Robert Su, Pharm.B., M.D.
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1. Derogar M, et al, “Increased Risk of Colorectal Cancer After Obesity Surgery.” Ann Surg. 2013 Mar 6. [Epub ahead of print]
2. Baker MT, “The history and evolution of bariatric surgical procedures.”
3. American Society for Metabolic and Bariatric Surgery, “Story of Obesity Surgery – On the Horizon and Summary.”
4. The Endocrine Society, “Bariatric Surgery in Diabetic Adults Improves Insulin Sensitivity Better than Diet.”
5. Ahlin S, et al, “Bariatric Surgery and Long-term Cardiovascular Events.” January 4, 2012, Sjöström et al. 307 (1): 56 — JAMA
6. Christou NV et al, “Bariatric surgery reduces cancer risk in morbidly obese patients.” Surg Obes Relat Dis. 2008 Nov-Dec;4(6):691-5. Epub 2008 Sep 20.
7. Lars Sjöström L, et al, “Lifestyle, Diabetes, and Cardiovascular Risk Factors 10 Years after Bariatric Surgery.” New England Journal of Medicine 351;26. December 23, 2004.
8. Consumer Guide to Bariatric Surgery, “Weight Loss Surgery News.”
9. Kling J, “Bariatric Surgery May Have Halo Effect on Family Members.”
10. Arterbum DE, et al, “A Multisite Study of Long-term Remission and Relapse of Type 2 Diabetes Mellitus Following Gastric Bypass” Obesity Surgery, January 2013, Volume 23, Issue 1, pp 93-102
11. MedlinePlus, “Your diet after gastric bypass surgery”
12. Addorisio D, “The Post-surgery Diet for Bariatric Patients: What to Expect.”
13. Su, R, “Bariatric Surgery: Credits Go To Restricting Carbohydrate Absorption.” published on January 20 and 27, 2010.