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The Truth about the BMI

by Laura Cipullo, RD, CDE, CEDRD, CDN, Whole Nutrition Services

 

BMI is a term you might have heard of — through either your doctor or a health article or maybe even your child’s teacher. If you don’t know what it is, the initials stand for Body Mass Index, and it is determined by making a calculation using your height and weight. The BMI categories are Underweight (any BMI less than 18.5), Normal (18.5-24.9), Overweight (25-29.9) and Obese (30 or more). These categories are taken very seriously by some in the medical community. The Harvard School of Medicine believes that measuring BMI can tell you if a person is at a “healthy weight,” while WebMD says “it’s important for your health to understand what it is and to know your number.”  Yet Perelman School of Medicine, University of Pennsylvania researchers believe it does not accurately measure body fat content, or consider attributes like muscle mass, bone density, overall body composition, race and gender. The BBC says that by itself, BMI can’t predict what diseases we will or won’t get.

I believe the BMI can be both misleading and quite damaging. This is something I speak about at length in the Women’s Health Body Clock Diet and my former blogs at Mom Dishes It Out and Laura Cipullo LLC. I certainly do not use it to measure my own, my clients’ or my children’s health.

The BMI reduces poor health to being caused by just one issue – weight. With its’ categories, it clumps bodies to fit into “healthy” and “not healthy” boxes when the science doesn’t always back that up. These categories can lead you to assume that everything above a 24.9 is a problem. But this is not proven. In adults, only BMI measurements of more than 35 or less than 18.5 are affiliated with higher mortality. In fact, as TIME points out,  “some studies show that people with higher BMI tend to be healthier and have lower premature death rates than those with lower BMI.” Overweight and healthy are not mutually exclusive categories. It is entirely possible to be both. And it is possible to be thin and unhealthy. Researchers from Oxford Brookes University discovered that more than a third of 3,000 people who were measured as having a “normal, healthy” BMI were potentially likely to have cardiovascular disease, something you might think only affects those who are overweight. Athletes also may naturally have a higher BMI, and even the CDC admits that it is not sure the overall BMI requirements should extend to them. The CDC’s list of health consequences associated with a high BMI also do not necessarily apply to everyone whose BMI is higher than 30: Mental illness, certain types of cancer, and low quality of life are a few of the things a person with a high BMI is supposedly at risk of, but I’m sure there are plenty of folks in this category who are living and will continue to live happy, healthy lives with BMIs over 30, and many affected by those issues who have a “normal” BMI.

You can see, then, how taking the BMI as gospel could lead you down a dangerous road. Your health choices are your own, but I would personally not see a healthcare professional who uses the BMI as a health tool.

Health is a complicated thing, and it’s not something that can always be relegated to numbers. We have to see the bigger picture, and that’s what the Health at Every Size movement is all about. BMIs can make a person obsessed with numbers, which is such a terrible thing to do to folks who already feel biased against for being a certain weight. People with eating disorders fight daily with an obsession to hit a certain number on a scale, and an obsession with hitting a BMI can lead to similar negative consequences. Dieting to get to a lower BMI can be physically dangerous as well. As I mentioned in the Women’s Health Body Clock Diet, “The famed Framingham Heart Study showed that weight cycling (aka yo-yoing) as a result of restrictive dieting is something that is indeed associated with higher mortality and cardiac disease. It’s actually healthier to be at a higher set weight than to allow your weight to fluctuate up and down by 20 pounds.” Putting pressure on your child to be at a certain BMI can set them up for an unhealthy relationship with food for life. Remember that as a parent you are a role model. Don’t put your child on any kind of fad diet in an effort to achieve any arbitrary weight goals. Body dissatisfaction, body shaming and eating disorders are some of the things a focus on BMI can do to kids.

That being said, you should know that there is a chance your child will get screened for BMI in school. One agency – the Institute of Medicine – endorses that, but others – including the CDC– do not. New York, Arkansas and California are some of the states that do BMI screening for children in schools. BMIs are also part of the FitnessGram. If your child does bring the results of a BMI screening from school, consider asking your child if they have any questions about this screening. Whatever you do, don’t place urgency on it and restrict your child. Be curious. Ask yourself questions such as, Is my child active on a daily basis? Does my child eat in respect to his/her body? Does my child eat all foods without guilt? Does my child hide their food? This is not a question of how many veggies are they eating. Rather, is your child getting caught up in using food or restricting food for emotional reasons? Any concern you have about your child’s health should be discussed with your pediatrician and/or registered dietitian specializing in the prevention and treatment of eating disorders or HAES. And always remember, choose healthcare professionals who share the same All Foods Fit, All Bodies Fit value system you do.