Official guidelines have long recommended that we should aim to stay a ‘normal weight’ for our size and age if we want to remain in good health.

However, the results of a recent international study challenge this view – they suggest that slightly overweight people may live longer than their slimmer counterparts.

The study of almost three million people by the US Centers for Disease Control and Prevention found that, while obesity increases the risk of dying early, being ‘slightly overweight’ appears to extend life.

Indeed, people with a body mass index (BMI) of 25-29 (officially overweight) were six per cent less likely to die than any other group in the study. This is a BMI that would give proportions similar to that of chart-topping singer Adele – slightly chubby rather than obese – on average, about 10kg heavier than what doctors tend to call “normal” weight.

THE MORE THINGS CHANGE

However, the severely obese – those with a BMI higher than 35 – were a shocking 29 per cent more likely to die by the end of the study than those of normal weight.

This US study was a systematic review that aimed to summarise existing research in the area, such as a Canadian study, published in the journal Obesity. That study found that underweight people (with a BMI of less than 18.5) had the highest risk of dying, morbidly obese people had the second-highest risk, but slightly overweight people had a lower risk of dying than those of normal weight.

One theory for these seemingly counterintuitive findings is that a little extra weight might protect the elderly when their health is ailing – by acting as padding when they fall, thereby preventing fractures. Fat reserves might also help older people survive longer when they develop life-threatening diseases.

JUST THE FACTS

Professor David Haslam, chairman of the UK-based National Obesity Forum, says the study was part of a strand of research that experts call the “obesity paradox”.

‘Occasionally, a study appears to contradict the view that being obese is detrimental to your health,” he says.

However, he stresses that the new study, which was published in the Journal of the American Medical Association (JAMA), was not a green light to overeat, and he points out that it had only looked at death rate and not rates of health and disease.

He adds that the results of this study may also be skewed because it uses BMI, an imperfect measure of fatness that ignores fat distribution and muscle bulk: it cannot determine, for example, whether weight is muscle or dangerous tummy fat. Plus some people may be of so-called “normal” weight because they have a chronic illness such as cancer.

THE OBESITY PARADOX

Some studies show that, for some people, a little extra weight may extend life, possibly because

  • People who can rely on fat reserves may fare better if they fall ill when they are older.
  • Health risks such as high blood pressure, heart problems and diabetes are often picked up and treated earlier in overweight people because they are monitored more often.
  • Research shows it may be better to stay a bit fatter than to constantly yo-yo diet.
  • Some people’s genes may protect them against the health consequences of being slightly chubby.
  • Extra weight may help the elderly survive falls unscathed.
  • Some slightly overweight people may be healthier than those who constantly starve themselves or smoke to suppress their appetite and stay thin.

THE WHOLE STORY

The increase in life expectancy for the slightly overweight is also modest and doesn’t necessarily mean they had better health or better quality of life than others in the study. So it might mean living longer but suffering from more weight-related conditions such as diabetes, painful joints and high blood pressure.

Another limitation is that the study combined all causes of death, rather than the risks of dying from diseases associated with excessive weight, such as heart disease.

‘There might be an obesity paradox, but you can’t conclude from it that people in the normal weight range should deliberately try to put on a bit of weight so they can live longer,’ says Professor Haslam. ‘The consensus is that avoiding obesity and – above everything – eating a healthy, balanced diet is best for most people’s health,’ he adds.

UNDER PRESSURE

Physiotherapist Sammy Margo says it’s also important to remember that being overweight can bring added stresses and strains to your body – particularly your joints – that can reduce quality of life, but the study hasn’t taken account of this.

‘I would also caution that when people are a bit overweight, very often that creeps into being a lot overweight as they gradually pile on the pounds over the years.

‘You are more likely to avoid morbid obesity and its associated health risks if you aim to keep your weight within the “normal” weight range,’ she says.

‘Good health is more than a BMI number – it’s feeling better because you have a healthy lifestyle, eat well and are physically active and less stressed,’ she adds.

Indeed, if you are tempted to quit running and instead eat a big, fatty burger or a luscious cake, don’t: the consensus is that it’s unwise to interpret this study as proof that being chubby is, in and of itself, healthy.

Rather, it may show that being slightly overweight is slightly less unhealthy than previously thought and it definitely shows that being very overweight increases your risk of early death. So keep running, stay in shape and enjoy life.

HOW DOES BEING A BIT OVERWEIGHT AFFECT YOUR RUNNING?

Physiotherapist Sammy Margo says that your joints are subjected to eight to ten times your body load when you run. Hence, the heavier you are, the more stress you put on your body. She says that being a little overweight isn’t of great concern for your joints when you are running, but staying a normal weight is still better for your body when you exercise. ‘Every pound you lose, you reduce your risk of injury,’ she says. ‘That’s reason enough to make sure you stay within a healthy weight range.’

Running coach Judith Ladd advises caution if you are above normal weight. ‘If you are new to running, start slowly to protect your joints – just running for one minute and walking for one minute, and then gradually run for longer and further. If you are carrying weight, don’t suddenly up the intensity or distance of your running, because every foot strike carries higher impact on your joints if you are heavier.’ It’s also important to have a gait analysis and to wear the correct trainers.

‘Running at a higher intensity than usual may feel good on your heart and lungs, but it also carries greater risk for your knees and joints if you are overweight, because it takes time to build up neuromuscular endurance,’ says Ladd.

‘However tempting it is to go hard, always take it slowly to allow your bones, joints and muscles to catch up with your aerobic fitness and your enthusiasm for running.’

Words by Liz Hollis