In other words, is it time to say goodbye to BMI?
That’s exactly what a new study looked at. It was done by researchers from the University of Virginia, published recently in the British Journal of Sports Medicine (13th November 2024).
The Study
The study (Weeldreyer, 2024), was a systematic review and meta-analysis of research looking at whether cardiorespiratory fitness or body mass index (BMI) had a bigger effect on cardiovascular disease and all-cause mortality risk.
They were looking at this because obesity rates have increased significantly over the past four decades, with roughly two in five adults now classified as overweight or obese. With that, more people are at risk of cardiovascular disease and mortality.
Public health strategy tends to involve promoting weight loss to increase health outcomes for these people. The problem? Many regain weight within 10 years, and intentional weight loss alone has not consistently shown improvements in mortality risk.
One thing that has been proven to reduce the risk of cardiovascular disease and death is being fit – so much so that the authors of this study suggested it could be the fifth ‘vital sign’.
So, they analysed 20 articles, looking at a very large number of people (a total of 398,716).
The Results
The main result from this study is that overweight-fit and obese-fit people had the same risk of all-cause mortality as normal weight-fit individuals. A closer deep dive into the stats showed:
- Compared with normal weight-fit individuals, there was a two-fold increased risk of all-cause mortality in unfit people who were normal weight, overweight and obese.
- Similarly, compared with normal weight-fit individuals, there was no greater risk for cardiovascular disease in fit people who were overweight or obese.
- Unfit people who were normal weight, overweight and obese had a 2-3 fold increased risk of cardiovascular disease.
Dr Angadi, the lead researcher, said,
Our study found that obese fit individuals had a risk of death that was similar to that of normal weight fit individuals and close to one-half that of normal weight unfit individuals”
Conclusion
The results demonstrated a significant reduction in both CVD and all-cause mortality risk in fit compared with unfit individuals – regardless of BMI. These results add to a growing body of evidence that higher cardiovascular fitness is a positive predictor of longevity. It may not be time to drop BMI yet. But the relationship between weight and survival seems more complex than first thought.
