"The Body Roundness Index is a novel body composition measurement that is touted as being a more accurate alternative to Body Mass Index."
The calculation is based on height and weight, and waist and hip circumference.
"In a large retrospective study of 33,000 US adults, researchers found a 'U-shaped' curve, indicating those with a Body Roundness Index below and above the normal range had an increased risk of death from any cause."
So... don't be a ball... or a twig.