The saddest thing about the world’s obesity epidemic is that so many children, some very young, are getting fat, and this is a new development over the last twenty years.

I said in my last blog that we don’t know what causes obesity. Well, some scientists now think they do.

The conventional wisdom is that people eat too much because they want to – they have no “self-control”.  And then they get fat, because if you eat more than you need the energy will have to be stored, and it will be stored as fat. But can that really apply to children? No child wants to be fat – they suffer teasing and get ostracized by their peers and have a lower quality of life than their thin schoolmates.

The alternative idea, that I mentioned in my previous blog, is that people get fat because of their biochemistry and the type of food they eat, and then their bodies tell them to eat more. So eating too much is a result of the obesity, not the cause.

And scientists are finding out why this might be.

Insulin is the problem. It is a very important hormone in the body; it is what we produce when we eat sugar, as insulin is essential to get sugar into the cells where it is used to release energy for use by the body. In most people insulin is well regulated, but in many obese people the fact that they have been eating the wrong diet has caused the system to go awry, and the body makes too much insulin. Insulin is also the fat making hormone – it diverts more of the sugar to be set down as fat.  So even if children eat the same foods as their thin schoolmates they will get fatter.

It gets worse as over time as the body gets used to these high insulin levels and the cells become insulin resistant, setting off a cascade of reactions.

We all have a switch in our brains telling us that our food stores are full and we don’t need to eat; this is activated as a result of biochemical signals (insulin again and another signaling substance, leptin), coming from our food stores. But in these children the excess insulin paradoxically acts against lepton’s signal that the food stores are full and prevents the switch working, resulting in increased food intake and decreased physical activity. In fact the brain is mislead into thinking the body is starving.

So these children have no choice in the matter – they have to eat. Their behaviour isn’t really under their control any more. The excess insulin acting on the brain also increases pleasure derived from food even when their bodies’ store of energy is full.

It gets into a really vicious circle. Eating more carbohydrate and especially sugars increases the supply of insulin (to allow more sugar into the cells). The more insulin there is, the fatter people get, until eventually the supply of insulin dries up and diabetes is the result.

So these children overeat because they have to, not because they are greedy. If they don’t overeat they will feel tired, hungry and have no energy.

We doctors have been telling people that all they have to do is to eat less and exercise more. But it isn’t really their fault that they can’t do it. The over eating is a result of their obesity not its cause.

We know that dieting does not work for most people over the long term. We know that many attempts at dieting reach a plateau after 3 -4 months, and scientists have found that this is because the insulin has caused the body to think it is being starved. The starvation response reduces expenditure of energy and increases the amount of food energy going to fat. This happens in adults as well and even when drugs are used to help lose weight.

So how do some children, and adults of course, get this abnormality?

We know it is partly inherited. Some racial groups have a much higher incidence of obesity than others – African-Americans, some native Americans, some Polynesians and so on. It is related to insulin resistance which is the underlying cause of diabetes. But scientists now think that many of us can develop this condition if we continually eat the wrong foods. Our diets now can make us produce too much insulin, which over the long term in children can cause this syndrome.

So what are these foods?

We all know now that the worst offenders are free sugars or sugar sweetened beverages. Our bodies are not equipped to deal with so much sugar. Sugar was first refined thousands of years ago, and before that we could only eat the sugar we found in fruit and honey. Since that time more and more sugar has been refined and in the developed countries sugar is a huge component of our diets. Modern fruit drinks contain much more sugar than they used to, and this plus the modern tendency to try to eat less fat so that we end up eating more carbohydrate, has resulted in an overload of sugars.

And of course lack of exercise is also a factor, as now children have lots of interesting things to do with their computer games, social networking and texting, that they don’t ever get bored and can stay in their chairs all day.

How have we got into this situation, that we are causing so much ill health to our children? You can’t really blame the food companies. You have to blame our culture and the faulty science that we have been promoting all these years.

No one has had time to individually prepare meals using fresh ingredients. People are busy making ends meet, with both parents working. Food companies therefore produce food which can easily be put on the table or the tray. Scientists told them that they should reduce fat, because lipids and cholesterol are known to cause heart attacks in older people. The fat in food is the tasty bit, so if you take out the fat, it doesn’t taste good, and people won’t buy it. So the food companies put sugar in it instead and this makes it tasty. So any ready meal, any sauce in a bottle will be high in sugar and carbs. Add in the drinks and you have a perfect recipe for obesity.

So what can be done about it?

The easy bit for a parent to do is to get rid of the sweet drinks. They aren’t necessary “for energy” even for sports, as scientists have proved that they don’t improve sports performance.  They just mess up your sugar balance. Perhaps governments could help by putting pressure on the drinks companies, or taxing high sugar content drinks.

It will be more difficult to get people to alter their diet to reduce sugar and other carbs. The injunction “eat real food” is easy to say, but difficult to do. It takes more time and it can be expensive. Protein, as I said in the previous blog, is expensive because meat especially is a very inefficient way of eating calories and very bad for the environment. Poor people have to eat carbohydrates. And as there are more mouths to feed in the world, especially in the developing world that want to eat more meat, richer people in the west will have to eat more carbohydrate as well.

But one thing should change. If you are obese and go to your doctor, she should not blame you. With more understanding, obese adults should be able to get more useful advice than just “eat less and exercise more”. And perhaps a new generation of children can be prevented from getting obese in the first place.

AUGUST 2006 VOL 2 NO 8 LUSTIG NATURE CLINICAL PRACTICE ENDOCRINOLOGY & METABOLISM 451