The Truth About Fat: Horizon BBC2 20th March 2012

This was a programme by Gabriel Weston who is a surgeon with an interest in obesity.  We are all eating too much and getting fatter. It is an epidemic.  But we are not all the same shape.   It is all a bit random.  Why do some people balloon but others stay slim despite the fact that we are all exposed to the same amount of food?  It’s a good question.

Food is everywhere.  Most of us are eating about 200 calories more per day than we should do.  A quarter of the adult population is clinically obese.  Fat is just the body’s way of storing energy, so it isn’t an intrinsically bad thing.  Subcutaneous fat is the stuff just under your skin but it isn’t particularly dangerous to your health.  It is the visceral fat gathered around the organs is the stuff that causes the problem.  It leads to a surge of cytokines that send messages to the rest of your body that can lead to diseases including diabetes.

Carle Le Roux is a researcher who has come up with some new ideas based on his own experience.  He used to be a shot putter, but found it hard to build up his weight.  His body seemed to have a sort of ‘set point’.  His group looked at hormones, the chemical messengers that control our body’s day to day activity.  They discovered two new hormones that modify hunger and fullness.

To illustrate it he starved Gabriel for a day then took a blood sample.  As soon as she had given the sample she immediately tucked into the sweetest food available, showing just how hungry she was.  The Her hormones matched her food intake.  The hunger hormone level went down when she ate and the fulness hormone went up.  This was what you would expect for a normally shaped person like her.  It turns out that the same hormones in obese patients don’t respond as quickly, so they don’t experience the same variation in hunger and fullness, and so just keep on eating.

Is it just genetic?

Studies in identical twins show that they generally have the same weight, which shows that genetics does play a very big part.  But they found a few exceptions.  So if obesity is genetic, what  is going on?  It turns out that the obesity gene has to be present, but it also has to be activated.  The study of this kind of thing is called epigenetics and there is a bit of a buzz about it in science at the moment.  Some genes need certain conditions to activate them.  Stress seems to be trigger in this case.  The implication is that there is a switch, and it might be a switch that can be turned off again once it has been turned on.

They are also studying how what happens to mothers affects their offspring.  The time in the womb can have a big effect on the child’s later chances of suffering obesity.  If the mother eats sparingly or has an unbalanced diet, the baby is born light.  But the chances of  becoming obese later grow considerably, presumably an adaptation to being born into a food poor environment.

So what can be done about it?  Dieting isn’t really doing much. A more drastic solution is a gastric bypass that reduces the size of the stomach.  This would reduce the ability to absorb food, but also seems to affect people’s appetite.  It can change the patient’s life.  Typically they lose a third of their weight and keep it off for at least 20 years.

They interviewed a woman who had had one now felt full after eating a meal and no longer liked sweet and fatty food.  It looked like the operation on her stomach had also affected her brain.  And this can be investigated as well.  MRI techniques can study what is going on inside people’s brains. Fat people have a much bigger response to fatty food than people with normal weight.  After gastric band surgery the brain response is transformed to that of a normal person.

It was really thought provoking stuff.  My first reaction was it really showed that obesity is a medical problem not a moral failing.  Some people do simply have different make ups that predispose them in a particular direction.  It is also intriguing how close we might be to some effective treatment for the people affected, though sadly it isn’t here yet.  Definitely an eye opener.

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