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Is the BMI good for your health?

There are few individual health measures that seem to weigh as much as body mass index or BMI. We encounter him not only in doctor’s offices, but also with online calculators and intelligent scales, in fitness studios and even then Determination of eligibility for the Covid vaccine.

The formula is simple: take your weight (in kilograms) and divide by the square of your height (in meters).

The result, which puts you in one of four main categories, should describe your body in one or two words: underweight (BMI under 18.5), normal weight (18.5-24.9), overweight (25.0-29, 9) or obesity (30 or higher).

After speaking with an epidemiologist, two obesity medicine doctors, a health psychologist, and a sociologist, none of them claimed that BMI was a very useful measure of a person’s health.

Indeed, some said they would call it a scam.

How is the BMI useful?

The calculation was introduced in the 1830s by a Belgian statistician who wanted to describe the “average man” quantitatively. It was known as the body mass index and was invented by Minnesota physiologist Dr. Popularized Ancel Keys. At the time, Keys was irritated that life insurance companies estimated people’s body fat, and therefore the risk of death, by comparing their weight with the average weight of other people of the same height, age, and sex. In a 1972 study of more than 7,000 healthy men, mostly middle-aged men, Keys and colleagues showed that the body mass index was a more accurate and far simpler predictor of body fat than the methods used by the insurance industry.

“It’s a very useful tool in epidemiological research,” says Dr. JoAnn Manson, Professor of Medicine at Harvard Medical School. Research has shown that in large groups of people, a higher BMI is generally linked to a higher risk of heart disease, type 2 diabetes, and some types of cancer, she says. On average, people with a higher body mass index have more body fat, so it can be useful to keep track of obesity rates, which have nearly tripled worldwide in the past few decades. It also has a “J-shaped” relationship with mortality; Very low and very high BMIs are associated with a higher risk of death, while the range “normal” to “overweight” is associated with a lower risk of death.

As Keys noted, BMI is also easy and inexpensive to measure, which is why it is still used in research studies and medical offices today.

Does it accurately describe individual health?

Despite its usefulness as a research tool, the body mass index is “pretty much useless when you look at the individual,” says Dr. Yoni Freedhoff, Associate Professor of Family Medicine at the University of Ottawa.

For example, BMI can’t tell what percentage of a person’s weight comes from their fat, muscles, or bones. This explains why muscle athletes often have a high BMI despite having little body fat. And as people get older, it’s common to lose muscle and bone mass but gain belly fat, a body composition change that would be harmful to health but could go unnoticed if it doesn’t change a person’s BMI, Manson says.

The measure also does a poor job of predicting a person’s metabolic health. In a 2016 study of more than 40,000 adults in the United States, researchers compared people’s BMIs to more specific measures of their health, such as insulin resistance, markers of inflammation and blood pressure, triglyceride, cholesterol, and glucose levels. Almost half of those classified as overweight and around a quarter of those classified as obese were metabolically healthy as a result of these measures. On the other hand, 31 percent of people with a “normal” body mass index were metabolically unhealthy.

BMI can “characterize a large portion of our population as somehow deviant because of their weight, even if they are perfectly healthy,” says A Janet Tomiyama, lead study author and associate professor of health psychology at the University of California. Los Angeles.

Another problem with BMI is that it was developed and validated primarily in white men, says Sabrina Strings, an associate professor of sociology at the University of California at Irvine. However, body composition and its relationship to health can vary based on gender, race, and ethnicity. “Women and people of color are largely not represented in much of this data,” says Strings. “Still, they are used to create a universal standard.”

Can the BMI be harmful?

This can be the case if it is used to set any height target posts. Dr. Rekha Kumar, Associate Professor of Clinical Medicine at Weill Cornell Medical College, says that some patients who have lost weight and achieved what they consider to be their “healthy, happy weight” but still have a high BMI, possibly that Feeling like you need to drop more pounds unnecessarily or unrealistically to be considered normal on the scales.

It can also be harmful for a doctor to assume that a person with a normal body mass index is healthy and not examine them for potentially unhealthy habits they may have, such as poor diet or insufficient physical activity, says Freedhoff. And if doctors of patients with higher BMI only focus on weight as the cause of health problems, they may miss more important diagnoses and risk stigmatizing patients.

There is plenty of evidence to suggest that weight stigma is harmful, says Tomiyama. Research has shown that doctors often have an anti-fat tendency, which can lead to poorer care and result in patients avoiding or delaying medical treatment. People who have felt discriminated against because of their higher weight are also around two and a half times more likely to suffer from mood or anxiety disorders, gain weight more often and have a shorter life expectancy.

“You can see a situation where this hyperfocus on body mass index and the fact that there are allowable and non-allowable BMIs could be very stigmatizing,” says Tomiyama. “And that stigma, ironically, could fuel future weight gain.”

What if BMI isn’t important to health monitoring?

If you’re worried about your weight, the more direct and relevant measure of potentially unhealthy body fat is to measure your waist circumference, says Manson. This appreciates the belly fat that is deep in the abdomen and that accumulates around vital organs. In addition, it can increase your risk of certain obesity-related conditions such as type 2 diabetes, high blood pressure, and coronary artery disease. It’s also more harmful than subcutaneous fat – the soft fat that you can pinch with your fingers and that is in a layer just below the skin.

In Freedhoff’s clinic for weight management, however, he and his team do not set any patient goals at all in terms of BMI, weight or waist circumference.

“We are discussing what we call ‘best weight’. This is the weight a person attains when leading the healthiest life that they can actually enjoy,” he says. If a patient’s weight is adversely affecting their health or quality of life, Freedhoff and colleagues will investigate strategies for weight loss, including lifestyle changes, medication, or in some cases, surgery. If not, Freedhoff tells patients that regardless of their BMI, they may already be a healthy weight.

Rather than focusing on height as a measure of health, Tomiyama says blood sugar, triglyceride, and blood pressure results can be better windows of wellbeing. How you feel in your body is also important, she says. “Can you go up a flight of stairs and feel good about how you feel afterward? How can you live your life in the body that you have? ” She asks.

When looking for better health, prioritize behaviors that are more under your control than your body mass index, says Tomiyama, such as “better sleep, more exercise, managing stress, and more fruits and vegetables eat”. – New York Times

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