BMI Obesity Readings May Be Inaccurate for People Over 40

A recent study presented at the European Congress on Obesity reveals that BMI may not accurately reflect obesity in people over 40, as age-related changes in body composition can lead to underestimations of body fat. Researchers recommend adjusting the obesity BMI threshold for older adults to better assess health risks.

A new study presented at the European Congress on Obesity in Venice, Italy, suggests that the traditional body-mass index (BMI) may not accurately reflect obesity in individuals over 40. As people age, their body composition changes, leading to discrepancies between BMI and actual body fat content.

Study Details

Researchers from the University of Rome “Tor Vergata,” the University of Modena and Reggio Emilia in Italy, and the Beirut Arab University in Lebanon conducted a cross-sectional study involving 4,800 adults aged 40-80. Using dual X-ray absorptiometry (DXA) scans, they assessed body fat percentages, revealing significant differences compared to BMI measurements.

Key Findings:

• Participants:
  • Total: 4,800 adults (61% women)
  • Age Range: 40-80 years
• BMI Categories:
  • Normal weight (BMI 18.5-24.9): 1,087 participants
  • Overweight (BMI 25.0-29.9): 1,826 participants
  • Obese (BMI 30.0 and above): 1,887 participants
• Body Fat Percentage Cut-off Points:
  • Ages 40-59: 40%+ for women, 28%+ for men
  • Ages 60-79: 42%+ for women, 30%+ for men

Results:

• According to BMI, 38% of men and 41% of women were classified as obese.
• According to body fat percentage, 71% of men and 64% of women were classified as obese.
• Researchers recommend adjusting the obesity BMI threshold for people over 40 to a BMI of 27, rather than the current WHO standard of 30.

Limitations of BMI

BMI, a measure used for over a century, does not account for differences in muscle mass versus fat. This limitation is especially significant for individuals with high muscle mass, such as athletes, and for older adults who may experience muscle loss and increased body fat as they age.

Expert Opinions:

• Dr. Mir Ali, a bariatric surgeon, emphasizes that while BMI is easy to calculate, it is less accurate than other methods like DXA scans for measuring body fat.
• Melanie Murphy Richter, a registered dietitian nutritionist, points out that BMI does not distinguish between different types of fat, such as visceral fat, which is more dangerous and cannot be detected through BMI alone.

The study indicates that BMI standards for obesity may need to be adjusted for older adults to provide a more accurate assessment of health risks. Despite its ease of use, BMI’s limitations suggest the need for more comprehensive methods to evaluate body composition, especially in older populations.