Viewpoint: Benefits of bariatric surgery

Professor Basil Ammori discusses the influence of bariatric surgery on diabetes and heart disease.

Bariatric surgery may help with the co-morbidities associated with obesity (Photo: Author)
Bariatric surgery may help with the co-morbidities associated with obesity (Photo: Author)

GPs often have difficult conversations with obese patients about exercise and losing weight.

Some patients desperately want to lose weight but do not succeed. For weight loss and the associated comorbidities of obesity, such as type 2 diabetes mellitus (T2DM) and IHD, evidence suggests bariatric surgery may form part of the solution.

Obesity, T2DM and IHD often go hand-in-hand. Three-quarters of newly diagnosed T2DM and 30% of newly diagnosed IHD cases are obesity-related.1 The risk of both conditions rises with the increase in severity of obesity.2

Evidence is establishing that sustained weight loss, such as that induced by bariatric surgery, results in a high chance of remission or improvement of T2DM and improvement in risk factors for IHD.

A landmark publication in 1995 found that 83% of 146 patients with T2DM witnessed a complete remission of diabetes after gastric bypass.3

Gastric bypass surgery

Gastric bypass involves partition of the stomach to create a small pouch that reduces portion size, and the bypass of some of the intestine to reduce absorption.

This is considered the gold standard bariatric procedure and is performed by laparoscopic surgery. On average, it induces loss of two-thirds to three-quarters of excess weight.

It is also often associated with an immediate improvement in T2DM, so most clinicians stop or reduce medication straight after surgery.

This immediate improvement is related to changes in intestinal hormones, with a sustained rise in beneficial hormones that improve diabetes control, such as glucagon-like peptide 1, peptide YY and glucose-dependent insulinotropic polypeptide, and reduction in the hunger hormone ghrelin.4

Gastric banding

More limited weight loss, such as that seen after gastric banding – an operation that creates a small pouch by placing an adjustable band around the top end of the stomach – could result in remission of T2DM in approximately 50% of patients.5

Sleeve gastrectomy, which involves the removal of two-thirds to three-quarters of the stomach, also results in marked improvement and remission of T2DM.6 This is due to the marked reduction in the hunger hormone ghrelin and the loss of an average 50-65% excess weight.7

Risks of surgery

Gastric bypass and sleeve gastrectomy carry a small risk of leaking stomach or intestinal contents (one in 500 in our experience) that could be fatal (one in 700 in our experience).

Internal small bowel herniation and obstruction might occur in one in 150 patients after gastric bypass.

It is essential for patients to take the recommended vitamin and mineral supplements, to avoid deficiencies. Band slippage or erosion into the stomach, pouch dilation and port leakage or infection will require revision surgery in approximately one in 10 patients with a gastric band.

All operations carry a small risk of bleeding, DVT or infection. Surgery might not be advisable in high-risk candidates, such as those with severe cardiac or respiratory disease and those with inadequately controlled psychiatric illness. Evaluation by a multidisciplinary team is essential.

Evidence of benefits

The benefits of bariatric surgery for T2DM and weight loss are more pronounced after gastric bypass compared with sleeve gastrectomy or gastric banding, as randomised trials have shown.8 When combined with medical therapy, bariatric surgery achieves control of T2DM in a significantly greater proportion of patients compared with maximal drug therapy alone.9

In March 2011, the International Diabetes Federation recommended that the threshold for advising bariatric surgery in patients with poorly controlled T2DM should be reduced to include people with mild obesity.10

The significant weight loss induced by bariatric surgery has been associated with resolution of hypertension in most patients,11 as well as reduction in cholesterol levels, with a consequent reduction in the severity and future development of IHD.

In a comparative study of 1,035 patients who underwent bariatric surgery and 5,746 morbidly obese subjects who did not receive bariatric surgery and were followed up for five years, surgery resulted in significant reductions in the risks of IHD, T2DM, cancer and death.12

A study of 1,658 patients who underwent bariatric surgery and 1,771 obese matched controls followed up for 15 years showed that bariatric surgery was markedly more efficient than usual care in the prevention of T2DM in obese subjects.13

Another similarly designed study with 10 years of follow-up showed that the risk of death due to MI was halved with bariatric surgery,14 while another study showed that bariatric surgery reduced the incidence of MI in obese individuals with T2DM.15

  • Professor Ammori is honorary professor of surgery, University of Manchester, and a bariatric surgeon at Spire Manchester Hospital


1. National Audit Office. Tackling Obesity in England. February 2011.

2. Wilett WC, Dietz WH, Colditz GA. N Engl J Med 1999; 341: 427-34.

3. Pories WJ, Swanson MS, MacDonald KG et al. Ann Surg 1995; 222(3): 339-52.

4. Laferrere B, Teixeira J, McGinty J et al. J Clin Endocrinol Metab 2008; 93(7): 2479-85.

5. Dixon JB, O'Brien PE. Diabetes Care 2002; 25(2): 358-63.

6. Pirolla EH, Jureidini R, Barbosa ML et al. Am J Surg 2012; 203(6): 785-92.

7. Lee WJ, Chen CY, Chong K et al. Surg Obes Relat Dis 2011; 7(6): 683-90.

8. Li P, Fu P, Chen J et al. Hepatogastroenterology 2012; 60(121)

9. Schauer PR, Kashyap SR, Wolski K et al. N Engl J Med 2012; 366(17): 1567-76.

10. International Diabetes Federation 2011.

11. Frigg A, Peterli R, Peters T et al. Obesity Surgery 2004; 14(2): 216-23.

12. Christou NV, Sampalis JS, Liberman M et al. Ann Surg 2004; 240(3): 416-23.

13. Carlsson LM, Peltonen M, Ahlin S et al. N Engl J Med 2012; 367(8): 695-704.

14. Sjostrom L. Int J Obesity 2008; 32 Suppl 7: S93-7.

15. Romeo S, Maglio C, Burza MA et al. Diabetes Care 2012; 35(12): 2613-17.

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