Weight Management: What's a Healthy Weight?
MANY OF US HAVE A VAGUE idea that we could stand to lose a few pounds. We get bombarded with weight-loss messages all day long, and we’re urged to do it for both our health and to attain a certain standard of beauty that favors lean figures.
(GETTY IMAGES)But who actually needs to lose weight, and what exactly does it mean to be at a healthy weight? It’s not as simple as just stepping on the scale and seeing a magic number.
Measurements of a Healthy Weight
Discussions of a healthy weight often reference the BMI or Body Mass Index as a standard of judging what’s healthy or not 體脂磅. “BMI is currently used by medical professionals as a quick assessment to whether or not a person has a healthy weight,” says Antonette Hardie, a registered dietitian at the Ohio State University Wexner Medical Center in Columbus.
“BMI is thought to provide medical professionals with a sense of whether or not an individual is at risk for certain obesity-related chronic diseases, such as heart disease, high blood pressure, diabetes and other comorbidities,” she adds.
The reason why boils down to fat. The BMI is a quick and dirty way of calculating whether someone’s weight is out of proportion to their height. When that happens, it's often assumed that the person is carrying around excess fat – also called adipose tissue – which can elevate risk for several chronic conditions.
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Belly Fat
Carrying excess white fat – cells that are stored under the skin or around the organs may be dangerous. This is especially true when the excess fat accumulates around the midsection where the vital organs reside. Too much belly fat has been associated with an increased risk of heart disease, diabetes, cancer and dementia. That's because these fat stores are metabolically active, meaning that the fat functions like an endocrine organ, secreting hormones that influence how your body functions.
But even thin people who still conform to the BMI scale can be carrying around too much belly fat, which can increase their risk of chronic illness. It's all about where the fat is stored in the body and how it alters the way the metabolism works. Metabolism is the process by which your body converts calories from the food you eat into energy to power your activities and bodily functions each day. If you consume more calories than you need to meet those needs, your body will store the excess as fat. And that's the issue when it comes to being overweight.
The BMI is intended to help doctors spot patients who might need to shed some excess fat. Brenda Braslow, a registered dietitian nutritionist and certified diabetes care and education specialist with MyNetDiary, a calorie and exercise tracker launched in 2007, explains that the BMI is “primarily meant to be used as a screening tool to assess weight status.”
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Calculating Your BMI
You determine your BMI with a relatively simple calculation that divides your weight in kilograms by your height in meters squared: BMI = weight (kg)/height (m2). The National Institutes of Health also provides a free BMI calculator online.
You can use the resulting number to see which BMI category you fall into:
A BMI of less than 18.5 means you’re underweight.
A BMI of between 18.5 and 24.9 means you’re normal weight.
A BMI of 25 to 29.9 means you’re overweight.
A BMI of 30 or greater means you’re obese.
According to the BMI scale:
A 5’8” tall person who weighs 150 pounds has a BMI of 22.8 and is considered normal weight.
A 5’2” tall person at that same 150 pounds has a BMI of 27.4 and is in the middle of the overweight category.
The BMI does not consider the body type of either individual or whether their weight is mostly muscle or fat. Indeed, many Olympic athletes – who we tend to think of as the fittest of the fit – would register as overweight or obese according to the BMI scale because they have a larger proportion of strong muscles, which is denser than fat.