How healthy is it to be ‘fat but fit’?

‘No such thing as “fat but fit”, major study finds,’ ran the headline in the Guardian. The BBC report was even more emphatic. ‘Fat but fit is a big fat myth,’ it declared. Yet the foundation for these claims is shaky to say the least.

They were based on a press release put out by the European Congress of Obesity about a yet to be published study by a research team at the University of Birmingham.

Its novel finding related to cardiovascular disease. It looked at whether obese patients who were ‘metabolically healthy’ and who did not have diabetes, high blood pressure or raised blood fats (cholesterol) were at increased risk of the disease.

The researchers used routinely collected data from 3.5 million patients from general practices in Britain from 1995 with a follow-up period of 20 years.

They concluded that ‘metabolically healthy’ obese patients were 1.5 times as likely to develop cardiovascular disease and about twice as likely to suffer heart failure compared to ‘metabolically healthy’ lean patients. For example, if there are 50 cases of cardiovascular disease in 1,000 lean, healthy, non-smoking men aged 55 over the next 10 years, there would be 25 extra cases in the ‘metabolically healthy’ obese men.

This study does not prove you cannot be fat and fit because being at risk of cardiovascular disease is not the same as having a health problem or being unfit.

We know that increasing levels of body fat raise the risk, more so in men than women. We know that a lean smoker is more likely to get cardiovascular disease than an obese non-smoker, but that the combination of smoking and obesity is worse.

We also know that blood pressure and blood cholesterol increase with body weight and their relationship with cardiovascular disease is continuous (the higher the value, the greater the risk).

However, this latest risk estimate for cardiovascular disease associated with obesity is much greater than indicated by previous research. Earlier studies had suggested that a person’s risk could largely be calculating without including obesity, by relying on other factors such as age, blood pressure, smoking habit, family history, and the presence or absence of other medical conditions.

There are a few problems with the study, however. One weakness is that it used cut-offs to define elevated blood cholesterol and blood pressure. The study may therefore have underestimated the effect of obesity on these risk factors. A further limitation is that it did not appear to adjust for the impact of type-2 diabetes, a potent risk factor for future cardiovascular disease.

A proper interpretation of the study cannot be reached until it is published in a peer-reviewed journal.

So is it possible to be fat and fit? The answer is clearly yes, at least in the short term. Fitness is the ability to undertake daily activities and moderate exercise without getting out of breath. Being fit, even if fat, reduces the risk of dying prematurely as well as getting diabetes. It is sound advice to extol increased physical activity, including everyday activities such as walking, climbing stairs and standing rather than sitting.

Ideally, one should aim to maintain a healthy body weight throughout adult life. If your waistline is expanding my advice is to eat less. However, a certain amount of weight gain with age is almost inevitable, and so it is important to remain fit, even if you are fat, by taking regular exercise.