Health experts have debunked the idea that people can be overweight but medically fit, according to a study which is being presented at the European Congress on Obesity.

The research found that ‘healthy’ obese people are still at a higher risk of cardiovascular disease such as heart failure or stroke than people of normal weight.

The study, which was conducted by Dr Rishi Caleyachetty and colleagues at the University of Birmingham, UK, is being presented at the congress in Porto, Portugal, this week (17-20 May).

People with metabolically healthy obesity (MHO) - known as "fat but fit" - are clinically obese in terms of their body mass index (BMI), but do not have metabolic complications that usually come with obesity, such as abnormal blood fats, poor blood sugar control or diabetes, and high blood pressure.

The researchers used health records from 1995 to 2015 to assemble a cohort of 3.5m individuals aged 18 years or older and initially free from cardiovascular disease.

To determine metabolic health, they divided the population into groups according to BMI and the presence or absence of three metabolic abnormalities (diabetes, high blood pressure, and abnormal blood fats) which were added together to create a metabolic abnormalities score. To be classified as MHO, individuals had to have none of these metabolic abnormalities.

 The authors found that, compared to normal weight individuals with no metabolic abnormalities, individuals with MHO had a 50 per cent higher risk of coronary heart disease; a 7 per cent increased risk of cerebrovascular disease and a doubled risk of heart failure.

 The analysis also showed that the risk of cardiovascular disease events in obese individuals grew with increased number of metabolic abnormalities present.

The research also found that regular physical activity and less sedentary time reduces the build-up of dangerous liver fat.

 Dr Caleyachetty said: “This is the largest prospective study of the association between metabolically health obesity and cardiovascular disease events. Metabolically healthy obese individuals are at higher risk of coronary heart disease, cerebrovascular disease and heart failure than normal weight metabolically healthy individuals. The priority of health professionals should be to promote and facilitate weight loss among obese persons, regardless of the presence or absence of metabolic abnormalities.

“At the population-level, so-called metabolically healthy obesity is not a harmless condition and perhaps it is better not to use this term to describe an obese person, regardless of how many metabolic complications they have.”