Why Do Some People Never Seem to Get Fat?

BBC Article.

With the increase in the amount of people in the UK now classed as ‘clinically obese’, the obsession with our weight has reached epidemic proportions. Despite the amount of advice and diets available, Sir Liam Donaldson, Chief Medical Officer for England, has said that we are facing an ‘obesity time-bomb’.

In order to find out why some people gain weight rapidly whilst others can eat whatever they like and never gain an ounce, Ethan Sims, a Medical Researcher, carried out an experiment in 1967 at a Vermont State Prison in the USA.

He recruited inmates to take part in the experiment by eating as much as they could in order to gain 25% of their body weight in exchange for an early release from prison.

Despite eating 10,000 calories a day, some of the volunteers could not reach their target weight, resulting in Ethan Sims declaring that obesity was near impossible for some people.

With this in mind, the BBC recently conducted an experiment for their program ‘Horizon’, using 10 slim volunteers (who were not on a diet) to eat as much high fat food as possible without doing any exercise and severely limiting how much they walked during the experiment.

One volunteer, Medical Student Katherine Hanan, stated that she had always been able to eat whatever she liked without putting on weight.

‘I’ve always eaten whatever I want and have always been slim. I’m really lucky and my friends hate me’ she said. Katherine had never been on a diet or done any significant exercise.

During the experiment, the volunteers were asked to double the amount of food they normally eat to see what happened. This meant eating around 3,500 calories for women and 5,000 for men which was easier for some but not for others.

One volunteer, Thomas, found it easy to eat the amount required as he was used to doing it in preparation for a run, but the ban on exercise was extremely difficult for him.

The volunteers were limited to 5,000 steps per day and some of them were physically sick with the amount of food they needed to consume for the experiment. Other volunteers found that they just couldn’t eat the amounts needed to reach the required calorie intake.

After 4 weeks, Katherine had gained almost 7% of her body weight and Thomas had gained 9%.

The outcome of the experiment could support the theory of Dr Rudy Leibel of Columbia University in New York, that we all have a natural biological weight that our bodies will stick to. He says that 50% of our weight is down to our genes and the other 50% is down to the environment that we live in.

Think of it like a thermometer, in that everyone has a certain point that is normal for them.

To emphasise the different ways our bodies behave towards access calories, out of the 2 volunteers that struggled to eat the excess food, one gained 1% in body weight whilst the other actually saw their body fat go down despite putting on some weight.

One expert, Professor Jane Wardle, puts it all down to a gene which can influence appetite leading some people to overeat and others to stop once they are full.

In one volunteer, the excess weight had been converted into muscle instead of fat as his metabolic rate had risen 30%. The reason for this is also down to genetics – something none of us have any control over.

This increase in muscle also explains why some people don’t look any different despite putting on weight and the same can be said for people who lose weight and nobody notices.

Our weight thermometer controls our ‘normal’ levels and many of the volunteers found that they went back to their previous weight naturally without having to do any excessive exercise or dieting.

The moral of the report (as far as I can see) is that we should all stop beating ourselves up about our weight and concentrate on eating healthily and getting a good level of exercise. It is so easy to lose motivation when dieting without putting ourselves under pressure for something that is all in the genes.

Read the full report on the BBC website