If your waist is more than half your height, you are in the 'overfat' category. REUTERS/David Gray

Having too much belly fat is the overwhelming norm in many developed countries, with as few as 10% of men and 20% of women having a healthy amount. While the overall obesity crisis appears to be levelling off, the proportion of people with unhealthy amounts of abdominal fat is still rising.

You might have an idea if you are overweight or obese – but you might not know that you can be of normal weight and still 'overfat'. Unlike the better known classifications, this is a measurement of belly fat, which is more harmful than fat stored elsewhere on the body.

Most people have an idea of whether they are underweight, healthy weight, overweight or obese. More than a quarter of the world's population is overweight or obese. Those are categories based on Body Mass Index (BMI) measurements, which take into account your height and overall weight. But BMI is far from perfect as a way to find out who is at risk of conditions such as diabetes, cardiovascular disease or cancer because of excess weight.

For example, BMI measurements don't take into account the amount of fat versus muscle you have. Athletes can come out with high BMIs despite having very little excess fat, because they carry a lot of muscle. But a sprinter's high BMI isn't going to be putting them at high risk of the health complications that come with being overweight or obese.

The overfat measurement isn't based on overall weight, like BMI is. Instead, it's simply that if your waist measurement if more than half your height, then you are overfat. This measurement focuses on abdominal fat, which is linked to an increased risk of illness and death compared with fat distributed more evenly over the body. Importantly, people can have a normal overall weight and still be overfat if they carry it disproportionately around their middles.

A new study finds that 90% of American men and 80% of American women are overfat. In addition, half of US children are thought to be overfat. Previous work has shown that excess weight in childhood and adolescence is very difficult to shift in later life due to habits formed as the brain is in its most formative phase.

The US, New Zealand, Greece and Iceland were the most overfat nations for men, all with more than 90% falling into the category. Women in those nations had less of a problem with abdominal fat than the men, but still with the high rates of 82%, 80%, 71% and 81%, respectively. About 50% of children in those four countries were overfat.

The prevalence found in the study is much higher than in other recent estimations, due to an increasing proportion of people with high levels of abdominal fat and a focus on BMI rather than overfat measurements.

"Reliance on BMI for determination of being overweight and obese may misclassify up to 50% or more of patients with excess body fat who may have increased health risks," the authors write in the study.

Greater efforts are needed to ensure people are clinically identified as at risk of health problems due to high levels of abdominal fat, despite not being overweight or obese, they write.

"The global overfat pandemic is a serious public health crisis that places a substantial burden on economic resources in developed countries," the authors write.

"Abdominal overfat is the most unhealthful form of this condition, so it is concerning that average waist circumference measures, generally indicative of abdominal overfat, have increased. Despite a levelling off appearance of being overweight and/or obese in some developed countries, the overfat pandemic continues to grow."

Budget 2017
Half of children in several developed nations have too much belly fat, putting them at risk of debilitating health complications. iStock