Type 2 diabetes and the gastric sleeve: what studies show

If you live with type 2 diabetes, a gastric sleeve may affect more than your weight. Many people hope it will lower their blood sugar, or let them cut back on medicines. Here is what long-term studies show, in plain language, including what they do not show.

Why weight and blood sugar are linked

Extra body fat makes it harder for insulin to do its job, so blood sugar rises. Losing a large amount of weight can help insulin work better again. After a sleeve, people eat much less and lose weight, and for many of them, blood sugar improves.

Canadian guidelines say bariatric surgery, together with medical care, can control type 2 diabetes better than medical care alone. They also say surgery should be considered for people with a BMI of 30 to 35 whose type 2 diabetes stays poorly controlled even with good medical treatment.

What the trials found

• In the STAMPEDE trial in the U.S., 150 people with type 2 diabetes were randomly assigned to medicines alone, a gastric bypass or a sleeve. After five years, 23% of people who had a sleeve had an A1C (a three-month blood sugar average) of 6% or lower, with or without diabetes medicines, compared with 5% of people on medicines alone.
• In the same trial, people who had a sleeve lost about 19% of their body weight on average, compared with 5% on medicines alone, and their use of insulin dropped more.
• In the Finnish SLEEVEPASS trial, 10 years after a sleeve, 26% of people who had type 2 diabetes before surgery were in remission.
• A pooled analysis of four U.S. trials, with sleeve, bypass and gastric band operations, followed people for up to 12 years. At 7 years, 18% of people who had surgery were in remission, compared with 6% of people treated with medicines and lifestyle changes. At 12 years, it was 13% compared with none.

Surgery also has downsides. In the same 12-year analysis, anemia, bone fractures and digestive problems were more common after surgery.

What remission means

Remission means your blood sugar stays below the diabetes range without diabetes medicines. It is not the same as a cure. Canadian guidelines note that the effect of surgery on blood sugar tends to fade over time for some people, and that diabetes can come back. That is why blood sugar checks continue for years after surgery.

Studies also suggest that remission is more likely when diabetes has been present for a shorter time and when the starting BMI is higher. Your surgeon can talk through what this may mean for you.

Before and after surgery

• Before surgery, your team looks at how well your diabetes is controlled, and may work with your family doctor to improve it.
• During the low-calorie diet before surgery, and in the first weeks after it, your diabetes medicines may need to change, sometimes a lot. Your team gives you a plan.
• Check your blood sugar as often as your team asks, and learn the signs of low blood sugar, such as shaking, sweating, confusion or a fast heartbeat.
• After surgery, keep your regular diabetes checkups with your family doctor, even if your blood sugar is normal.

Questions to ask your care team

• How might a sleeve affect my diabetes, given how long I have had it and the medicines I take?
• Is another procedure, such as SADI-⁠S, worth discussing for me?
• What is my plan for diabetes medicines during the pre-⁠op diet and after surgery?
• Who adjusts my medicines after I go home?