The idea of "healthy obesity" is a myth, a study of 3.5 million Britons suggests.

Having excess fat increases the risk of suffering heart disease by half - even when blood pressure and cholesterol levels are normal, according to the research.

People regarded as obese but healthy also have an increased risk of stroke and almost double the risk of heart failure, researchers found.

Experts have long debated whether or not people can truly be "healthy obese" or "fat but fit", characterised by having normal markers of metabolic health despite having a body mass index (BMI) of 30 or more.