(CNN) Excessively high or low body mass index measurements have been linked to an increased risk of dying from nearly every major cause except transport accidents, new research says.

The study , published Wednesday in The Lancet Diabetes and Endocrinology and conducted by scientists at London School of Hygiene and Tropical Medicine , revealed that BMI that's either too high or too low is tied to increased morbidity from a range of major diseases.

Krishnan Bhaskaran, lead author of the study and associate professor of statistical epidemiology, noted that his team found "important associations" between BMI and most causes of death.

"BMI is a key indicator of health. We know that BMI is linked to the risk of dying overall, but surprisingly little research has been conducted on the links to deaths from specific causes," he said.

"We have filled this knowledge gap to help researchers, patients and doctors better understand how underweight and excess weight might be associated with diseases such as cancer, respiratory disease and liver disease."

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