Recent research suggests that the waist-to-hip ratio (WHR) is a better predictor of critical health outcomes, such as cancer, heart disease, and mortality, compared to the traditionally used body mass index (BMI).
Historically, BMI has been the primary tool for evaluating an individual’s weight and overall health. However, its accuracy and usefulness have been challenged in recent times, with some claiming it might even be misleading.
In a study released in JAMA earlier this month, lead author Dr. Guillaume Paré, a professor of medicine at McMaster University, and his team aimed to identify the most effective metric for determining risk factors associated with chronic diseases. They compared the effectiveness of WHR, BMI, and fat mass index (FMI) in assessing mortality risks. The goal was to determine which of these measures had the most robust and consistent correlation with lifespan.
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Waist-to-Hip Ratio vs. BMI: A Study’s Findings
Analyzing health data from nearly 400,000 individuals with an average age of 60, sourced from the UK Biobank, researchers endeavored to determine the most accurate health indicator. This Biobank provides an expansive collection of anonymous health data for around half a million UK residents.
The team utilized Mendelian randomization in their study, factoring in obesity-linked genetic variants. Their objective was to identify an adiposity marker, indicative of stored body fat, that showed a strong, direct, and consistent link with health results.
The findings revealed that the waist-to-hip ratio (WHR) consistently demonstrated the most significant association with both overall and specific-cause mortality. Notably, this correlation was more pronounced in men. Additionally, a potential causal link was identified between WHR and mortality risk.
Elaborating on their methodology, Dr. Paré stated, “Given that previous research primarily utilized mortality as a key health metric, we followed suit.” He added, “Our analysis highlighted WHR’s superior performance across all our set criteria.” Essentially, their research suggests WHR to be a more telling health indicator than BMI.
Dr. Paré emphasized that this study reinforces a growing consensus in the medical community about the superiority of WHR over BMI.
However, an external expert, Ryan Glatt, Director of the FitBrain Program at Pacific Neuroscience Institute in California, highlighted a limitation. He pointed out that the study’s demographic was restricted to Caucasian Europeans, which might not reflect the broader global population.
Should We Rethink Using BMI as a Health Metric?
Dr. Paré believes that the use of BMI as a health indicator might be outdated. He suggests that the waist-to-hip ratio (WHR) is a more accurate marker for determining body fat. He pointed out the flaw in BMI; it doesn’t factor in the composition of the body, which can misrepresent the body fat levels in short and tall individuals.
The National Heart, Lung, and Blood Institute echoes this sentiment, noting that BMI might misjudge the body fat in athletes with a muscular physique and underestimate it in elderly people or those with reduced muscle mass.
Mike Matthews, a certified personal trainer and author of “Bigger, Leaner, Stronger”, highlighted that one of BMI’s significant drawbacks is its inability to differentiate between muscle and fat. This makes it a questionable measure for those with a muscular build. He further emphasized that BMI often underestimates the level of overweight in individuals compared to methods like assessing body fat percentage. Citing past research, Matthews revealed that many individuals classified as “average weight” or “overweight” by BMI standards were actually clinically obese when considering their actual body fat percentage. In essence, he suggests, “BMI offers a more optimistic view of health than what might be the reality.”
However, shifting away from BMI isn’t straightforward. Dr. Paré mentioned the challenges of such a transition, especially given that BMI has deep roots in medical procedures, from determining eligibility for weight loss surgeries to diagnosing specific eating disorders. “Transitioning to WHR wouldn’t be a simple change,” he expressed.
On the other hand, Glatt believes that while BMI has its limitations, it shouldn’t be disregarded entirely. Instead, it should be considered alongside other health markers and demographics to provide a more comprehensive view of an individual’s overall health.
Understanding the Waist-to-Hip Ratio: A Simple Guide
Calculating the waist-to-hip ratio (WHR) is straightforward, and there are informative videos available to guide you, as Dr. Paré highlights.
General guidelines suggest that for men, a WHR less than 0.95 and for women, less than 0.80, indicate a reduced risk of health complications like heart disease. However, Dr. Paré notes that these benchmarks may require adjustments based on race and ethnicity.
Here’s how the National Heart, Lung, and Blood Institute suggests you calculate your WHR:
- Stand Upright: Ensure you’re standing in a neutral position, not slouching.
- Waist Measurement: Using a tape measure, find the narrowest part of your torso, typically situated midway between your lowest rib and hip bone. Wrap the tape measure around this point, ensuring it’s parallel to the ground.
- Hip Measurement: Measure the circumference of the broadest part of your hips, which includes the fullest part of your buttocks and thighs.
- Calculate WHR: Divide the waist measurement by the hip measurement to get your WHR.
For accurate results, experts recommend:
- Consistency in Measurement Zones: Always measure the same areas to maintain precision.
- Maintain a Regular Timing: Your body measurements can vary during the day due to factors like fluid intake and perspiration. To maintain consistency, measure at the same time each day.
- Proper Tape Position: The tape measure should lay flat against your skin, neither too snug nor too loose.
Ryan Glatt emphasizes that while WHR is a valuable metric, it shouldn’t be the sole determinant of health outcomes. It’s merely one of many tools health professionals utilize to gauge your risk of diseases.
- Surrogate Adiposity Markers and Mortality
- Assessing Your Weight and Health Risk
- Accuracy of body mass index in diagnosing obesity in the adult general population