Is Weight Just a Number? What Experts Say Really Matters When It Comes to Health

Between celebrities shilling appetite suppressants and reality shows extolling extreme weight loss at any cost, it may seem like seeing the right number on the scale is the golden ticket to total health and happiness. But recent cultural debate and a growing body of research suggests that measuring your weight is just one piece of the wellness puzzle.

Numerous studies in the last few years have challenged long-held beliefs that bodyweight is an absolute measure of overall health. A 2014 systematic review of various studies included the finding that a significant portion of people classified as obese are metabolically healthy (with no signs of insulin resistance or elevated blood pressure or cholesterol). A 2016 study found that “people with healthy obesity have lower risks for diabetes, CHD [coronary heart disease], stroke, and mortality” than unhealthy subjects who may not be obese. With so much conflicting information, it’s no wonder you might be confused.

“I find that people tend to obsess about the number on the scale,” says Boston-based family medicine doctor, Michael Richardson, MD., “but it may not be a true representation of their health (especially for athletes), and a lack of weight loss progress can be incredibly demotivating and derail individuals trying actively to improve their health.”

Instead, experts agree it’s the patterns or trends you can see in your weight overtime and the healthy habits you take on that matter most.

Why Weight and BMI Don’t Equate Exactly to Health

It’s important to understand that when people casually talk about “weight” and its association to health, they could be talking about a number of things—very often, it’s the actual number on the scale (weight) or the body mass index (BMI), a person’s weight in kilograms divided by the square of their height in meters. While BMI is commonly used to assess weight categories (“underweight,” “normal/healthy,” “overweight,” and “obese”) that could be associated with certain health conditions, the Centers for Disease Control (CDC) points out that it’s “not diagnostic of the body fatness or health of an individual.” While the concepts of weight and BMI are related, Richardson says they have very different meanings and implications for health.

“If we emphasize weight and BMI, we are missing out on all the other aspects that impact health, such as physical activity, the quality of food eaten, and more,” he says. “BMI and weight can be useful tools for assessing a person’s size, but health is better measured by improvement and maintenance of healthy behaviors.”

One big problem with using only weight or BMI to define health is the risk of “weight bias” or “weight stigma”—a.k.a. “negative attitudes towards, and beliefs about, others because of their weight…manifested by stereotypes and/or prejudice towards people with overweight and obesity,” according to the WHO. “Weight stigma has a negative impact on one’s mental health and can lead to the avoidance of health care, potentially causing people—especially women—to miss out on preventative screenings and early health-condition interventions,” says Natalie Jovanovski, a postdoctoral researcher at Australia’s Swinburne University. And when people fall outside of the accepted weight norms, the “failure” to measure up can fuel body dissatisfaction and lead to compulsive dieting, exercising, and body monitoring, she says.

Internalizing the message that weight loss should be the ultimate goal of all healthy behaviors can lead to engaging in typically-beneficial behaviors, like working out, for all the wrong reasons, says Jovanovski. “Research suggests that solely focusing on exercise to change one’s body shape, weight, or size, or obsessively monitoring one’s behaviors, is detrimental to health and wellbeing, and doesn’t recognize our innate need to move and participate in physical activity for the purposes of enjoyment and social connection,” she says.

Making Sense of Mixed Science  

While many health experts still rely on BMI to quickly check a person’s weight status, many admit the tool isn’t ideal because it doesn’t tell the whole story. So why do doctors and other health experts still use it?

“Doctors use BMI to quickly assess if someone is overweight or obese, but we also recognize this measure is imperfect and does not necessarily describe how fat is distributed in the body, how fat is utilized, or the overall calorie imbalance in a person’s diet,” says Richardson. “Some studies have found that metabolically healthy obese people (being obese but with normal cholesterol levels, blood sugar, and blood pressure) have a minimal increased risk of heart disease, and in some scenarios, have a reduced risk of death compared to normal weight individuals.”

Richardson says this is what experts call ‘The Obesity Paradox.’ But, to confuse matters more, some studies have found strong evidence that directly opposes the Obesity Paradox, like a recent paper published in JAMA Cardiology. “It showed overweight and obese people were not only at higher risk of cardiac death, but had fewer ‘healthy life years’ when compared to normal weight people,” explains Richardson.  

“The data clearly shows that obesity is associated with heart disease, diabetes, and early death, but the cause of these poor health outcomes may be due to the behaviors that lead to obesity, not a person’s size,” says Richardson. “Lack of exercise, overeating, and other negative behaviors can significantly harm our health due to their effect on blood pressure, cholesterol, body fat, and blood sugar. By solely looking at BMI, a calculation based on height and weight, we are not capturing a person’s whole health, their different risk factors, or the impact these risks have on the body.”

Fitbit’s in-house dietitian Tracy Morris agrees that the simplicity and accessibility of BMI makes it an appealing tool, but she doesn’t dwell on it. “Measuring someone’s weight and height are very quick and easy, and you can use those numbers to get an initial idea of whether or not they are carrying a healthy weight for their frame,” she says. “But a person’s BMI doesn’t paint the full picture of their health. It tells us nothing about their body composition—is that extra weight mostly unhealthy fat or mostly metabolically-active muscle? To figure this out, I’d get my clients to jump on a Fitbit Aria 2 scale. And where is the extra weight being carried? We know if it’s around the belly, it puts you at a higher risk of disease. A waist circumference measurement can help suss that out.”

Other Health Measurements to Consider

Because weight and BMI don’t take the social determinants of health into account, “such as whether somebody’s health is impacted by poverty, disability, stigma and discrimination, or other important factors,” Jovanovski believes a more accurate definition of “health” and overall wellness would encompass a combination of physical, psychological, and sociological measures. “These factors cannot be viewed separately,” she says.

According to Richardson, the key to better health isn’t in deprivation, but in fostering positive behaviors in every facet of life. “I recommend focusing on increasing healthy behaviors,” he says. “If a person is able to quit smoking, eat fewer processed foods, and incorporate more activity in their daily life, I’m not very worried if the number on the scale doesn’t shift. I know they are improving their health in the long term, and weight changes will come over time.”

Getting started on a healthier path and making healthy habits stick doesn’t have to be complicated. “Strapping on a Fitbit device and tracking your daily activity is a great place to begin,” says Morris. “From there it’s all about taking small steps towards your goals—swap out candy for fruit, soft drinks for water, and make choices that help you to be more active, like parking in the farthest spot, and inviting your girlfriends to a dance class instead of a boozy happy hour.”

When healthy habits become a lifestyle, the number on the scale can go back to being exactly what it is—one little metric about your body, not some crazy number that defines your health or who you are.

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