In people with heart disease, having a body mass index around 27 is linked to the lowest chance of dying from any cause, while both lower and higher BMIs are associated with higher risks.

The pattern where both very low and very high body mass index increase death risk in heart disease patients holds true regardless of whether they smoke, are physically active, or have different education levels.

People with heart disease who are obese (BMI 30 or higher) have a 23% higher chance of dying from any cause compared to those who are overweight (BMI 25-30).

People who are too thin have a much higher chance of dying early—even more than those who are obese—suggesting being underweight is just as dangerous as being very overweight.