Body Mass Index (BMI) and Surgery

It’s rare that I’ll do surgery on someone whose BMI is over 35.  Why is that, exactly?

What is BMI?

BMI (body mass index) is a rough estimate of body fat.  It combines a person’s height and weight into one number as a way to help provide a picture of overall health.  The easiest way to determine your BMI is to use an online calculator like this one: BMI calculator .  If you want to do it the old-fashioned way, here’s the formula:  multiply your weight in pounds by 703.  Divide that number by your height in inches squared.  BMI can be used to compare the overall body fat and health of people of differing heights and weights.  For instance, a person who is 6 feet tall and weighs 170 pounds has the same BMI as a person who is 5 feet 6 inches tall and weighs 140 pounds.

Body mass index is not a perfect measure of body fat or health.  It provides an instant ‘snapshot’ of a person’s general health, but it’s just a rough estimate.  Clearly other things factor into how healthy a person is and how much body fat she might have.  BMI may overestimate body fat in an athlete with a muscular build, for instance.  This is true also during pregnancy.

World Health Organization and BMI

The World Health Organization (WHO) uses BMI in determining whether a person is at, above, or below her ideal body weight.  According to the WHO, for people younger than 65, a healthy BMI is between 18.5 and 25.  The WHO classifies a person as ‘overweight’ if her BMI is between 25 and 30, and as ‘obese’ if her BMI is above 30.  At the turn of the century (in 2000) 30.5% of Americans were obese, or had a BMI over 30.  The Centers for Disease Control and Prevention (CDC) released a report in February 2020 indicating that the obesity rate in the United States is now 42.4%.  Almost one-half of all Americans have a BMI over 30.

BMI and surgery

Now that you know a little more about BMI, why is it that most plastic surgeons won’t operate on someone with a high BMI?  The answer:  it’s all about safety.  Countless studies have demonstrated that higher BMI’s are associated with increased risks of heart disease, high blood pressure, type 2 diabetes, breast cancer, colon cancer, prostate cancer, liver disease, gallstones, sleep apnea, and other breathing problems.  And those are just the medical  problems.  For instance, if you are put to sleep for surgery, the gases used by the anesthesiologist are absorbed by fat cells.  The larger your fat cells are, the more gas is absorbed.  Because of that, it takes longer to get the gas out of your body after surgery.  You wake up more slowly.  This increases your risk of having trouble breathing for longer periods of time after surgery.  Trouble breathing increases your risk of pneumonia and decreases your oxygen levels.  Your tissues need optimal oxygen levels to heal their best.

A person with a high BMI is at higher risk of complications from the surgery itself compared to a person with a BMI in the normal range.  Published studies indicate substantially increased risks of wound healing problems (wound “dehiscence”), infection, and fluid accumulation (“seroma”).  These types of problems cause anxiety, pain, and may require additional surgery.  Along with the added risks of additional surgery, there’s additional cost.

Certainly there are situations where a person has  to undergo surgery, regardless of her BMI.  Emergency surgery and cancer surgery are easy examples.  When it comes to more elective  surgery, however, BMI must be taken into consideration.  The cosmetic surgery procedures where this is most important are tummy tucks and mommy makeovers.

If you have a BMI over 30, it doesn’t mean you can’t have cosmetic surgery.  You might still be a candidate.  However, if you also have diabetes, high blood pressure, and  issues with your heart, the risks may just be too high.  When you call our office to schedule an appointment for cosmetic surgery, we ask a few questions.  While the questions may seem a bit personal, it’s really about health  and safety.  Specifically, your health and your safety.  I want to do surgery on people who are in good health.  BMI is one tool we use to gauge that.



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