Some associate obesity with anyone who is overweight, which is not necessarily true. Obesity is characterised by body mass which exceeds a certain percentage. Using the body mass index (BMI), a person’s weight in kilograms (kg) is divided by the person’s height in metres (m) squared to equal the percentage range in which one’s BMI should fall.

People that have a BMI of 30 or greater are generally considered obese, although very muscular people (especially young males), children and teenagers can be exceptions to this definition.

Normal Weight Obesity

Normal weight obesity is a condition of having normal body weight, but high body fat percentages and poses the same health risks as obesity.

Fat But Fit

You’ve probably heard someone say, ‘I’m fat but fit.’ Several recent studies have suggested this could be true, but a comprehensive review of these recent studies has found that ‘healthy obesity’ is just a myth.

Scientists know that overweight people can be what they call ‘metabolically healthy.’ This means that despite having a high body mass index, someone can have a small waistline, normal blood pressure and low cholesterol levels, and show little to no risk for developing diabetes. The opposite is also true; thin people can be metabolically unhealthy, with high blood pressure, high cholesterol and fat that accumulates only around their middle.

The researchers evaluated the eight studies, which included a total of more than 60,000 participants. All of the studies had recorded participants’ BMI and their metabolic status, as well as any fatal or nonfatal cardiovascular events, such as a heart attack.

The results

As they expected, the researchers found that their control group – the normal weight, metabolically healthy people – had the fewest cardiovascular events of all the groups.

They also found that being metabolically unhealthy puts you at a higher risk for cardiovascular disease, even if you’re in the normal BMI range. In fact, the metabolically unhealthy thin people had the same risk as the metabolically unhealthy obese group in the short-term.

Perhaps more surprising was that they found little difference in the risk for heart disease between metabolically healthy overweight individuals and metabolically healthy normal weight people. The same was true for metabolically healthy obese people.

The Fat but Fit myth was busted as this study could monitor participants over a longer period, and has changed the way experts are looking at Fat but Fit patients, previously not considered to be at a higher risk of obesity related disease and complications.

Generally speaking, the more body fat you’re carrying, the higher your health risk. However, the amount of weight gained throughout your adult years also contributes to the risk. For example, a middle-aged person who weighs 10 kg more than they did in their early 20s has an increased risk of high blood pressure, stroke, diabetes and coronary heart disease.