What's happening?

The office workers are counting down the minutes until lunchtime. It is the boss's birthday - and she has bought a giant chocolate cake to share with everyone.

This is the kind of thing that Professor Susan Jebb wants to stop. The food chief says that offering your co-workers cake is just as bad as smoking near them.

Cakes are high in sugar. In Britain, like many other countries, two in every three adults are overweight or obeseFor adults, obesity is defined as a Body Mass Index (BMI) of 30 or more. A BMI of 25 or more is classed as overweight..

But not everyone thinks we should listen to health advice. It is known for changing often - and some advice given in the past has turned out to be wrong.

In the 1800s, Austrians put a poison called arsenicA chemical element which is very poisonous. in their coffee. In the 1930s and 1940s, doctors said that smoking was a good way to help sore throats, even though we now know it causes many illnesses.

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Others point out that we know a lot more today than in the past. Modern health advice is much more likely to be helpful.

Can health advice be trusted?

Yes! Health advice is science - and sometimes, when we learn new things, we have to change our minds. The advice is right more often than it is wrong - and it has helped many people.

No! Advice is hardly ever perfect. Even if we choose to follow it, we should remember that it is not always right.