BMI for Gastric Sleeve: 2022 ASMBS/IFSO Requirements Explained

Under the 2022 guidelines from the two main surgical societies, ASMBS and IFSO, weight-loss surgery such as a gastric sleeve is recommended at a BMI of 35 or higher, whether or not you have obesity-related health problems. It should be considered at a BMI of 30 to 34.9 if you have metabolic disease or haven't kept weight off with other treatment. For people of Asian descent, the thresholds are lower: surgery should be offered from a BMI above 27.5 (ASMBS/IFSO 2022). Many U.S. insurers still use the older rule of a BMI of 40, or 35 with a related health problem.

The 2022 guidelines at a glance

The ASMBS and IFSO guidelines replaced the 1991 National Institutes of Health (NIH) consensus that had been the standard for three decades. They apply to metabolic and bariatric surgery (MBS) in general, which includes the sleeve and gastric bypass. Together, these two operations make up about 90% of weight-loss surgeries worldwide (ASMBS/IFSO 2022).

Sources: ASMBS/IFSO 2022 guidelines (Obesity Surgery version; also published in Surgery for Obesity and Related Diseases), ASMBS patient page.

A small detail: the guideline summary says "BMI > 35," while the ASMBS patient page says "BMI ≥35." In practice, a BMI of exactly 35 is treated as meeting the threshold on the ASMBS page.

Why the guidelines changed

The 2022 paper says the 1991 rule was "applied universally" by doctors, hospitals and insurers, but that hundreds of studies since then show surgery is safe and works across BMI classes. It gives a perioperative death rate of 0.03% to 0.2% (ASMBS/IFSO 2022). It also points out that BMI is only a rough measure of body fat. A person with a BMI of 30 whose fat sits around the organs may be at higher risk than a person with a BMI of 40 whose fat is mostly in the legs.

For people of Asian descent, diabetes and heart disease show up at lower BMIs. That is why the guideline says obesity starts at a BMI of 25 to 27.5 in this group, and that access to surgery should not be denied based only on the usual thresholds.

How to calculate your BMI

BMI is your weight in kilograms divided by your height in meters squared (NIDDK). In pounds and inches, MedlinePlus gives this method:

1. Multiply your weight in pounds by 703.
2. Divide that by your height in inches.
3. Divide by your height in inches again.

Example: a person who is 5 feet 11 inches (71 inches) tall and weighs 290 pounds: 290 × 703 = 203,870; ÷ 71 = 2,871; ÷ 71 = about 40.4. The ASMBS uses the same example and calls it "a BMI over 40" (ASMBS). You can also use the NHLBI BMI calculator, which labels a BMI of 30.0 or above as obesity.

Weight at each threshold, by height

The table shows the weight (in pounds) at which an adult reaches each BMI. We calculated it with the formula above and rounded to the nearest pound.

Age, teens and very high BMI

• Older adults: the guideline says there is "no evidence to support an age limit" for surgery, though surgeons should check for frailty (ASMBS/IFSO 2022).
• Teens: for children and teens, BMI is measured against growth charts. The guideline cites a recommendation to consider surgery when BMI is over 120% of the 95th percentile with a major health problem, or over 140% of the 95th percentile. The NIDDK adds that teens should be evaluated by a team with expertise in pediatrics.
• BMI over 60: the guideline says there is no agreement on the best operation at very high BMI, and that risk rises as BMI rises, but surgery has been shown to work in this group.

When surgery is a bridge to another treatment

Sometimes the reason for a sleeve is to make another treatment possible. The 2022 guideline gives examples (ASMBS/IFSO 2022):

• Hip or knee replacement: some orthopedic societies discourage joint replacement at a BMI over 40, and weight-loss surgery has been reported as a bridge.
• Large abdominal hernias: the guideline says weight-loss surgery should be considered first in people with severe obesity who need an elective hernia repair.
• Organ transplant: severe obesity can limit access to a transplant list. The guideline cites studies in which more than half of people with kidney failure and severe obesity could be listed for a kidney transplant within 5 years after surgery.

If one of these applies to you, bring a letter from the other specialist to your bariatric consult. It gives the surgeon the full picture.

What surgeons look at besides BMI

The guideline says a multidisciplinary team can help find and manage risk factors before surgery, and that the decision on readiness should mainly be the surgeon's. A dietitian can review your weight history and eating patterns and correct vitamin and mineral shortfalls before the operation (ASMBS/IFSO 2022). If you are having surgery abroad, ask whether the hospital has a dietitian and who will order your blood tests and vitamins once you are home.

U.S. insurance vs paying abroad

A guideline is not a coverage rule. The 2022 paper notes that insurers have used the 1991 thresholds as their standard. The NIDDK's patient page still lists the older-style criteria: a BMI of 40 or more, 35 or more with a serious health problem linked to obesity, or 30 or more with type 2 diabetes that is hard to control (NIDDK). Medicare says it covers some bariatric operations "if you're eligible," based on conditions related to morbid obesity (Medicare.gov). Check your own plan's written policy.

Some plans also require you to lose weight before surgery. The 2022 guideline is blunt about this: it says there are no data to support insurance-mandated weight loss before surgery and calls the practice "discriminatory, arbitrary, and scientifically unfounded" (ASMBS/IFSO 2022). Your insurer may still require it.

When you pay yourself, for example at a hospital in Mexico, no insurer stands between you and the surgeon, so the BMI rule you meet is whatever that surgeon uses. The medical question is the same in any country: does the expected benefit outweigh the risk for you? If a clinic offers surgery outside these ranges, ask why, and ask what follow-up you will get at home. Our guides to gastric sleeve in Mexico and whether a gastric sleeve in Mexico is safe cover how to check a hospital and surgeon.

BMI is the start, not the finish

The sleeve is the most common weight-loss operation in the U.S. The ASMBS estimates 157,254 sleeve procedures out of 270,089 bariatric operations in 2023 (ASMBS). Meeting a BMI threshold makes you a candidate, not an automatic yes. The NIDDK lists questions to think about first, such as whether you can commit to lifelong changes in eating, medical follow-up and vitamins (NIDDK). To compare options, read gastric sleeve vs gastric bypass and how much weight people lose after a sleeve.

Related reading

• Gastric sleeve revision