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Last Updated: Friday, 30 April, 2004, 22:58 GMT 23:58 UK
Why obesity gives you diabetes
By Pat Hagan

Waist measurement
Obesity is common among people with diabetes
IT seems like a fairly simple equation. If you eat too much you get fat and if you get fat you are more likely to suffer heart disease.

But the process by which the current obesity epidemic could lay waste to a whole generation of youngsters before their parents is not quite that straightforward.

In fact, it's the development of diabetes - a direct consequence of poor diet and inactive lifestyle - that is the crucial factor in this deadly chain of events.

Yet some experts are worried that the public's lack of understanding of this complex disease and how it relates to what we eat, could undermine any attempts to change children's dietary habits before it is too late.

"It's an area that needs a lot of work," said Dr Stephen Lawrence, a GP who is lead clinician for diabetes at Medway Primary Care Trust in Kent.

"The idea of curative medicine is easy to sell to the public.

"But with this we are saying if you do something now then the chances are you will not get this disease later in life.

"It involves a less sexy approach but at the moment we have one million people in the UK walking round with diabetes without even knowing it."

So how exactly does a fatty diet and excess weight lead to diabetes and, in turn, cardiovascular disease?

Stage one - Insulin resistance

Insulin is a hormone produced by the pancreas. It plays a crucial role in helping the body's cells mop up glucose from our diet and turn it into energy.

Dr Lawrence said: "Think of a corridor full of doors. You need a key to unlock each door so you can put a parcel (glucose) in each room. Well, insulin is that key."

The problem is that abdominal fat releases a particular protein - called TNF alpha - which 'messes up the mechanism of the lock', according to Dr Lawrence.

In other words, the body's cells become resistant to insulin.

The key point here is that the damaging protein is only released by the type of fat that gathers round the waist and not, for example, on the buttocks. So diet and lifestyle are crucial.

Stage two - Increased insulin production

Once the pancreas senses the insulin it is producing is not being used effectively, it compensates by making even more of the hormone.

This process can go undetected for years but is the building block for type two diabetes.

With cells becoming resistant to insulin and the pancreas overproducing, there are raised levels of the hormone in the blood.

Stage three - Insulin output drops

Eventually, the pancreas becomes exhausted and can no longer produce enough, or any, insulin.

"The pancreas cells have been producing far more insulin than in someone without diabetes and they eventually burn themselves out," said Dr Lawrence.

Even at this stage, you may have no symptoms at all. Some people get tired, thirsty and lack energy but many feel nothing.

Yet irreversible damage may already be under way to the heart, eyes and kidneys.

Stage four - Blood sugar levels rise

Without the insulin 'key', the glucose from our diet cannot be converted into energy and so blood sugar levels also start to rise.

Excess blood sugar is another key factor in the development of diabetes.

Stage five - Inflammation

This combination of factors - insulin resistance, reduced insulin production and raised blood sugar levels - eventually combines to have a devastating effect on the body's vital organs.

Blood pressure can go up, circulation can be affected and problems with vision can occur.

It's believed that much of this damage is due to inflammation in blood vessels triggered by the whole process.

As the lining of blood vessels becomes damaged - a process called atherosclerosis - the risk of arteries becoming blocked increases.

If they do, a heart attack could be inevitable.

What worries experts like Dr Lawrence is that few people may understand the connection between carrying a few extra pounds round the waist in early adulthood and the risk of life-threatening diabetes later on.

Yet the solution, he adds, is simple.

"The most important thing is to look at limiting weight gain and by taking regular aerobic exercise of at least 30 minutes three times a week."

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