‘Fat but fit’ is a myth, new study suggests

Thinking big: This map shows the percentage of the adult population classified as obese.

Scientists have long debated the extent to which weight impacts on health. Now a major study has found that overweight people are more at risk of heart disease. Should we take its advice?

Ten countries. Twelve years. Half a million people. A new study on the link between health and weight is certainly wide-ranging.

According to the work, people who are overweight or obese are 28% more likely to develop heart disease than those at a normal weight. The researchers controlled for other factors like blood pressure and cholesterol, suggesting that excessive weight is unhealthy in itself. Their finding is echoed by a similar study reported in May (but still unpublished).

This sounds like common sense — how often have we been told that thin is good and fat is bad? Last December, obesity was cited as one of the reasons why the life expectancy of Americans is falling. But the science behind fatness is far from settled; this new study is only the latest twist in a debate that has been raging for over a decade.

Scientists tend to agree that severe obesity is a health risk. For the moderately fat, however, things are less clear. In 2013, a major study found that overweight people actually live a little longer than their slimmer peers.

The true marks of fitness, it suggested, are not determined by how heavy you are. In other words, you can be “fat but fit”.

This study outraged many experts — one dismissed it as “a pile of rubbish”. Others supported it with similar findings. Few subjects are more divisive in the world of health.

One reason is that we still know little about how fat relates to the body’s functions. It seems to increase blood pressure and affect the production of insulin, leading to diabetes. On the other hand, it may help sustain the body through illness and cushion it against blows — but this is mostly speculation.

Another problem is that many studies — on both sides of the debate — rely on body mass index (BMI), a 185-year-old method for measuring weight adjusted for height. BMI has many shortcomings. For example, it cannot distinguish between fat and muscle, and the way it classifies people’s weight is arbitrary.

What should we make of all this?

Fat chance

“Time for a change,” say some. For too long, society has promoted slimness as an ideal, as if the science backed this up 100%. It does not. This ideal has more to do with old-fashioned notions of beauty than with health. Eating well and exercising are important, but nobody should be made to feel uncomfortable about their size.

“Don’t get carried away,” reply others. On the whole, the risks of being overweight have more basis in science than the benefits. The research may be inconclusive, and each individual is a different case, but that is no excuse to get as fat as we want. This new study is one of the biggest ever conducted. We should take it seriously.

You Decide

  1. Are you happy with your weight?
  2. Should we expect clear-cut advice from scientists?


  1. Calculate your BMI using the link in Become An Expert. Does the result reflect how you feel about yourself?
  2. Take up a new form of exercise over the next month. Keep a journal, noting how you feel. (The aim is not to lose weight, but to enjoy yourself in a healthy way.)

Some People Say...

“Research is what I’m doing when I don’t know what I am doing.”

— Wernher Von Braun

What do you think?

Q & A

What do we know?
That BMI is a crude way of measuring an individual’s health. To get a sense of what shape you are in, it helps to know your waist size, your blood pressure and sugar levels, your cardiovascular fitness, and so on. People naturally come in different shapes and sizes, so you do not necessarily need to worry if your BMI classifies you as “overweight” or “underweight”.
What do we not know?
Quite apart from the way in which fat interacts with health, there is another debate about how scientific findings should be presented to the public. Some argue that it is important to give people the full picture, even if it is unclear. Others say that simple messages — such as “Don’t let your BMI get above 25” — are less confusing and therefore more helpful. What do you think?

Word Watch

New study
Published in the European Heart Journal. The researchers looked at the health data of citizens in ten European nations.
In a study, variables related to what you are studying can sometimes distort your results. When researchers set up their study so as to minimise this distortion, they are said to “control” for the variables.
This means that the study’s findings have not yet been “peer reviewed” — ie, assessed and declared scientifically sound by experts.
The average life expectancy fell from 78.9 to 78.8 years between 2014 and 2015, according to the National Centre for Health Statistics.
Live a little longer
Those deemed “overweight” were 6% less likely to die across the study than those classified as “normal weight”.
Body mass index
Your BMI is your weight (in kilograms) divided by your height (in metres), then divided by it again. Those whose BMI falls below 18.5 are deemed “underweight”; 18.5–25 is “normal”; 25–30 is “overweight”; 30 and above is “obese”.
The boundaries of these categories (see above) have changed across time.


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