New Danish Research Challenges Assumptions About Overweight, Obesity, and Mortality Risk

Recent research presented at the European Association for the Study of Diabetes (EASD) annual meeting in Vienna, Austria, has provided fresh insights into the relationship between body weight and mortality risk. Traditionally, higher Body Mass Index (BMI) levels—such as overweight and obesity—have been associated with increased health risks, including heart disease, diabetes, and certain cancers. However, the Danish study suggests that this association might not be as straightforward as previously thought.

The study analyzed health data from over 85,000 individuals, predominantly women, with a median age of 66.4 years. The researchers found that people with a BMI in the overweight category and some with obesity were not more likely to die during the five-year follow-up period than those within a normal BMI range of 22.5–25.0 kg/m². Interestingly, the research also showed that individuals with a BMI at the lower or upper ends of the normal weight spectrum, as well as those underweight, had higher mortality rates.

Specifically, underweight individuals (BMI < 18.5) were nearly three times more likely to die compared to those in the healthy BMI range. Conversely, people with severe obesity (BMI 40 and above) had more than double the risk of mortality. Surprisingly, those in the overweight range (25–30 kg/m²) and the lower obese range (30–35 kg/m²) did not show an increased risk, a phenomenon sometimes termed "metabolically healthy obesity" or "fat but fit." However, BMI values between 35 and 40 kg/m² still correlated with a modest increase in mortality risk.

One key consideration highlighted by the researchers is the potential for reverse causation, where illness leads to weight loss, skewing the association between low BMI and higher mortality. Since many participants had health scans for existing issues, some of the findings could be influenced by pre-existing health conditions.

Furthermore, the study emphasizes that BMI alone is not the definitive indicator of health or body fat distribution. Fat stored deep within the abdomen—called visceral fat—can pose a higher health risk than fat stored in hips, thighs, or buttocks, even if BMI is similar. This underscores the importance of personalized health assessments, considering factors such as fat distribution and metabolic health when evaluating obesity treatment and health risks.

In conclusion, the findings challenge the traditional view that overweight and obesity are immediate threats to longevity. Instead, they suggest a nuanced understanding of weight-related health risks, especially in older adults, and highlight the importance of a comprehensive approach to health management.

Source: https://medicalxpress.com/news/2025-09-overweight-obesity-dont-early-death.html