Science Mom: ‘Fat’ Is Not The Opposite Of ‘Healthy’

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Myth: It’s as simple as calories in, calories out.

Reality: Even automobile engines don’t work this simply–the efficiency you get from your car depends on the temperature outside, the length of your drive, the type of traffic you’re driving it in, and many other factors besides how fast and far you’re driving it. Does it seem plausible that a mechanism as complex as the human body would somehow have a less complicated relationship with calories than a car engine would? Factors as far-ranging as the type of bacteria in your gut, the way your body produces hormones and regulates their levels, and the amount of sleep you’re able to get all have an effect on your body’s relationship with food, just as your diet and activity level do. Someone who ate and exercised exactly as much as you do might still end up weighing quite a bit more than you, or quite a bit less–so stop trying to act as if you can tell what someone ate for lunch or whether they hit the gym last night by eyeballing their waistline.

Myth: Skinny people live longer.

Very obese people do have higher rates of mortality than average-weight individuals. But guess what? So do underweight people. In fact, in a study comparing mortality rates among underweight, average-weight (referred to in the study as “normal weight”), overweight, and obese people, the group least likely to kick the bucket during the study was the “overweight” one.

Critics argue that the quality of life of overweight people is lower than that of those with average weight. Quality of life is certainly an important metric, but it’s easier to manage diabetes or heart disease in a living patient compared to the alternative.

Myth: Your BMI is an important and meaningful number for your health.

The BMI, or body mass index, was explicitly invented to compare large groups of people. It was never intended to be used as a judgment on whether or not an individual human being is a Skinny Minnie or a Fat Fatty Fatcake–and yet, chances are, your doctor’s office has your BMI recorded in your chart somewhere, and might even make prescriptions for your health based on those digits.

But your BMI doesn’t have any predictive value at all for your health. Yes, people who are obese have a high BMI, but a high BMI does not automatically mean you have a case of the OMGFATZ. You can be an athlete and have an “overweight” or “obese” BMI, because you know what’s extremely dense? Muscle. BMI also fails to take into account such characteristics as: having a pair of shoulders that wouldn’t look out of place on a linebacker. Giant knockers. Strong bones.

There are measurements that have predictive health value. You can measure your blood cholesterol, your blood glucose, your sodium titer. But those are lab tests, and lab tests cost money, which your insurance doesn’t want to pay for–why do fancy labwork when you can just shove someone on a scale and jot down their numbers? Well, because that fancy labwork actually has a lot more meaning for someone’s health, which is what a trip to the doctor is supposed to be about.

(Image: itVega / Shutterstock)

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