Obesity is a major health concern. The incidence is on the rise around the world, thanks to an abundance of ultra-processed food and lack of activity. And it’s affecting people from all corners of the globe. The health implications are even more concerning. Being overweight or obese leads to insulin resistance and a higher risk of diseases that insulin resistance fuels, like type 2 diabetes and cardiovascular disease.
Here’s the surprising part. Even people who think they’re healthy because their weight is normal can experience insulin resistance and poor metabolic health. Why? Because we use body weight and body mass index (BMI) to label people as obese or normal weight and it’s not the most reliable way to determine whether a person is metabolically healthy and their health risks.
There’s a condition called metabolically obese normal weight (MONW). People with MONW fall within the healthy BMI range, yet they are not metabolically healthy. They suffer from insulin resistance and prediabetes, which negatively impacts their health and future health risks. For example, they have a higher risk of developing type 2 diabetes and cardiovascular disease. But these normal-weight, metabolically unhealthy people slip through the system because we measure obesity by calculating BMI.
To address this issue, researchers from TAU’s Faculty of Medicine are taking a closer look at how we measure and think about obesity. As part of a large study, they looked at health data from about 3,000 folks, both women and men. In the process, they uncovered surprising findings that could change the way healthcare providers and others think about and measure obesity.
While body mass index (BMI) is still the standard by which healthcare providers measure body composition and health risks, it’s not reliable in all cases, as it can miss people with MONW. The study found that 40% of females who are normal weight by BMI standards and 25% of males are unhealthy from a metabolic standpoint. These men and women have issues like insulin resistance that place them at higher risk of health issues. Plus, they think they’re healthy based on their body weight.
To add to the confusion, some people deemed overweight or obese are not unhealthy from a metabolic standpoint. These individuals are overweight or obese, based on the scale, aren’t at greater risk of health problems because of their weight. BMI also misclassifies individuals from certain groups, such as Black and Asian populations, leading to potential misdiagnoses. So, you can’t reliably judge how metabolically healthy someone is based on their weight or BMI.
A better measure is body fat percentage, according to the researchers. This is the percentage of your body composition that’s fat. It’s a better indicator of whether someone’s healthy or at higher risk of cardiovascular disease and type 2 diabetes.
Is There a Better Measurement of “Obesity?”
Based on the results of this study, researchers point out that we can better assess metabolically significant obesity by measuring body fat percentages rather than relying on a standard scale or BMI measurement. Currently, the standard is to calculate BMI from a person’s height and weight. Body Mass Index (BMI) is a person’s weight in kilograms (or pounds) divided by the square of height in meters (or feet). You can plug the values into a BMI calculator, widely available online to find your own BMI. Instead, healthcare providers should measure body fat percentage. To do this, they could use electrical conductivity devices or calipers to measure skinfolds.
Why is body fat percentage a better measure? Body fat percentage distinguishes fat from muscle whereas body mass index (BMI) does not, as it only looks at weight and height. Based on BMI, an athlete or weightlifter could fall into the obese category because they have a high body weight relative to their height. Yet for the weightlifter, the weight is mostly muscle, rather than fat.
In the same way, an older person with a normal BMI based on calculation, might have enough muscle loss that they fall into the normal weight category, despite being overweight or obese with regard to body fat percentage. When they weigh themselves, they think they’re healthy because their body weight falls in the healthy range. It’s deceiving!
Using Waist Measurements to Determine Health Risks
Along with measuring body fat percentage, another useful measure is waist circumference. Knowing your waist size says something about how much visceral fat you have hiding deep in your belly. Visceral fat, also known as inflammatory fat, is especially harmful to your long-term health and it doesn’t get enough attention in the press. We tend to lump all fat together, rather than distinguishing between harmful fat, like visceral fat, and fatty tissue that’s less likely to harm your health.
Visceral fat is stealth fat you can’t see. It wraps around organs like your liver, kidneys, and pancreas and it’s more metabolically active. Visceral fat produces inflammatory chemicals that fuel insulin resistance and metabolic syndrome, which is why it’s so harmful.
At least one study shows that waist size is a better measure of metabolic health than body fat percentage and it’s an easy measurement to make. To measure your waist size accurately:
- Stand with your feet shoulder-width apart. Don’t slouch!
- Wrap the tape measure around your waist at the midpoint between your lowest rib and the top of your hip bone. Make sure the tape is horizontal to the floor and not tilted up or down.
- Take a normal breath and then exhale gently. Tighten the tape measure around your waist without pressing it into your skin too tightly or leaving it too loose.
- Record the measurement in inches or centimeters.
- For increased accuracy, repeat the measurement two or three times and take the average of the readings.
- Double-check that the tape measure is still at the correct midpoint and parallel to the floor before recording each reading.
How large is too large? Women who have a waist size greater than 35 inches are at higher risk of metabolic problems, like insulin resistance and cardiovascular disease, based on their waist measurement. If you’re a man, health risks rise with a waist size over 40 inches. Know your numbers!
Conclusion
BMI could be old news soon and there may be a new sheriff in town – body fat percentage. It could become the gold standard for screening for obesity. It tells us more about health risks than BMI, as it also measures muscle mass. Body fat percentage gives a better idea of body composition than BMI, which doesn’t distinguish between the two types of tissue.
References:
- Yair Lahav, Aviv Kfir, Yftach Gepner. The paradox of obesity with normal weight; a cross-sectional study. Frontiers in Nutrition, 2023; 10 DOI: 10.3389/fnut.2023.1173488.
- “Calculate Your BMI – Standard BMI Calculator – NHLBI, NIH.” https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm.
- “Body Mass Index (BMI) | Healthy Weight, Nutrition, and Physical ….” 03 Jun. 2022, https://www.cdc.gov/healthyweight/assessing/bmi/index.html.
- “Body Mass Index (BMI) In Adults | American Heart Association.” 01 Aug. 2014, https://www.heart.org/en/healthy-living/healthy-eating/losing-weight/bmi-in-adults.
- “Tool: BMI and waist circumference calculator – Mayo Clinic.” https://www.mayoclinic.org/diseases-conditions/obesity/in-depth/bmi-calculator/itt-20084938.
- “Measuring Obesity | Obesity Prevention Source | Harvard T.H. Chan ….” https://www.hsph.harvard.edu/obesity-prevention-source/obesity-definition/how-to-measure-body-fatness/.
- “Better Ways than BMI to Measure Obesity – Scientific American.” 05 Jul. 2023, https://www.scientificamerican.com/article/better-ways-than-bmi-to-measure-obesity/.
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