## Being Too Thin Can Be Deadlier Than Being Overweight,Danish Study Reveals
A recent Danish study has revealed a surprising link between body mass index (BMI) and mortality,finding that being underweight or at the lower end of a healthy weight range can be more perilous than being overweight,even reaching into the lower levels of obesity.The research, analyzing data from a large cohort, challenges conventional wisdom about weight and health.
The study followed participants and tracked mortality over time, with 7,555 (8%) experiencing death during the follow-up period. Researchers discovered individuals classified as underweight were 2.73 times more likely to die compared to those with a BMI between 22.5 and <25.0 kg/m2, which served as the reference population.
Surprisingly, the increased risk wasn’t limited to those severely underweight. Individuals with a BMI of 18.5 to <20.0 kg/m2 – at the lower end of the healthy weight range – faced double the risk of death compared to the reference group. Even those in the middle of the healthy range, with a BMI of 20.0 to <22.5 kg/m2, showed a 27% higher likelihood of mortality.
Conversely,the study found that individuals with a BMI in the overweight range (25 to <30 kg/m2) and those with a BMI in the lower obese range (30.0 to <35.0 kg/m2) experienced no increased risk of death compared to the reference population – a phenomenon sometimes described as being “metabolically healthy” or “fat but fit.” A BMI between 35 to <40.0 kg/m2 was associated with a slightly increased risk of death, at 23%. Those with a BMI of 40 kg/m2 and above (severe obesity) were more than twice as likely (2.1 times) to have died compared with the reference population.
The researchers, led by Dr. Gribsholt, were surprised to find no increased mortality associated with BMI up to 35 kg/m2, and only a slight increase for those between 35 and <40 kg/m2. “One possible reason for the results is reverse causation: some people may lose weight because of an underlying illness,” Dr. Gribsholt explained.”In those cases, it is indeed the illness, not the low weight itself, that increases the risk of death, which can make it look like having a higher BMI is protective.” The researchers acknowledge that, as the data came from individuals undergoing health scans, they cannot entirely rule out this possibility. They also suggest that protective traits in longer-living individuals with higher BMIs could influence the results.
Professor Bruun emphasized that BMI is not the sole indicator of health. ”Other critically important factors include how the fat is distributed,” he stated. Specifically, visceral fat – stored deep within the abdomen – is metabolically active and can negatively impact health. He explained that individuals with the same BMI can have vastly different health profiles depending on where their excess fat is located, with abdominal fat (“apple-shaped”) posing a greater risk than fat distributed on the hips and thighs.
The study underscores the need for personalized obesity treatment, taking into account factors like fat distribution and the presence of conditions like type 2 diabetes when setting weight goals.
All results were adjusted for sex, comorbidity level and education level, and the pattern remained consistent across different ages, sexes, and education levels.