Chancellor George Osborne has announced a new tax on the soft drinks industry, in an attempt to tackle the UK’s obesity crisis.

Manufacturers will be taxed according to the volume of the sugar-sweetened drinks they produce or import. Products will also be categorised into two bands according to whether they contain 5g of sugar per 100ml or 8g per 100ml.

The tax was announced following intense pressure on the Government from campaigners, including the chef Jamie Oliver.

What is sugar?

Sugar is obviously the crystalline white or brown substance that you sprinkle in your tea, or the powder that you puff over freshly baked cakes. But it also describes carbohydrates which provide energy. These are split into two groups: monosaccaride and disaccharide molecules.

These are further broken down into fructose and glucose found in fruits, vegetables, and honey; sucrose, or table sugar; lactose, found in milk, and maltose, known as malt sugar found in drinks such as beer.

Such molecules occur naturally in food such as fruit, or can be added during manufacturing, for example to chocolate.

Why is sugar harmful?

Unlike salt, sugar is not toxic in itself and it is only directly harmful to the teeth, according to Graham MacGregor, chair of Action on Sugar and Professor of Cardiovascular Medicine at the Wolfson Institute of Preventive Medicine at Queen Mary, University of London. The substance decays teeth, and is therefore the commonest cause of severe pain in children.

Eating sugar in moderate amounts in the form of complex carbohydrates is not harmful. However, if the energy gained by sugar is not used, the body will store it as fat. In turn, this can lead to obesity which can trigger type 2 diabetes as the body becomes resistant to insulin.

The amounts of sugar in food and drink Show all 6 1 /6 The amounts of sugar in food and drink The amounts of sugar in food and drink Minstrels A 42g bag contains 28.9g of sugar The amounts of sugar in food and drink Dairy Milk A 49g bar contains 26.8g of sugar The amounts of sugar in food and drink Skittles 45g of Skittles (about a quarter of a large 174g pouch) contains 40.4g of sugar The amounts of sugar in food and drink Ribena A 500ml bottle of Blackcurrant Ribena contains 23g of sugar, down from 50g/500ml after it was reformulated to avoid the government's tax on sugary drinks The amounts of sugar in food and drink Coca Cola A 330ml can of Coca Cola contains 35g of sugar The amounts of sugar in food and drink Innocent Smoothies A 250ml bottle of strawberries & bananas Innocent Smoothie (the middle size) contains 26g of sugar

What does it do to your body?

When we digest sugar, enzymes in the small intestine break it down into glucose.

This glucose is then released into the bloodstream, where it is transported to tissue cells in our muscles and organs and converted into energy.

Beta cells in the pancreas constantly monitor the amount of glucose in the bloodstream and release insulin to control it.

This means that if you consume more sugar than your body needs right away, it can be stored for later to keep your blood-sugar levels constant.

If your body stops producing any or enough insulin, or if your cells become resistant to it, this can result in diabetes, leaving your blood-sugar levels to rise to dangerous levels.

What happens to your body?

Sugar is essential for the human body as it powers the cells that keep us alive. However, eating too much of it can also have a negative effect on our health. Foods with added sugar that does not occur naturally contain empty calories, meaning that they have no other benefit than to provide energy. If we eat more sugar than our energy levels require, then our bodies have to find something else to do with it, creating a whole host of problems. Excessive sugar consumption is one of the leading causes of obesity, heart disease and diabetes.

Why do we crave sugar?

You get a sugar “high” when your blood sugar spikes after eating a large amount of carbohydrates.

This is followed by a crash where insulin drives the sugar out of the blood and into your muscles for energy.

However, different forms of sugar create different effects. Table sugar creates a faster spike than complex carbohydrates found in brown rice, for example, Abigail Wilson, a member of the British Dietetic Association and CEO of Isos Health, said.

“You need some sugar in your bloodstream to function. However if you skip meals your blood sugar levels will become low resulting in you craving foods such as simple carbohydrates,” said Ms Wilson.

We crave this feeling because we need to keep the equivalent of around 2 teaspoons of “sugar” in our bloodstream at a time for our body to function normally. But if we consume large meals containing sugar, our bodies react by producing large amounts of insult in order to process the substance.

"Once we stop eating the sugary meal we then may have an excess of insulin in the blood stream that causes our blood sugars to drop further and make us feel hungry again," said Ms Wilson.

What sugar should be avoided at all costs?

Ms Wilson said she would above all avoid consuming sugar drinks as fluids should only be a source of hydration, and not energy.

“Drinking sugary drinks do not have nutritional benefits and adds unneeded calories,” she said.

What should be done about sugar?

The steps taken to reformulate foods to cut the salt content is what needs to be repeated for sugar, said Professor MacGregor. This would involve setting the food industry targets to reduce sugar in food and drink gradually over several years. This allows conumsers’ pallets to adapt to the different flavour, and gives manufacturers time to change their practices.

Action on Sugar is calling for a 50 per cent reduction in sugar over five years, and 20 per cent in fat over five years. That would lower the calorie intake by around 200 calories per person per day: stopping people from becoming obese and developing type 2 diabetes.

Malcolm Clark, co-ordinator of the Children’s Food Campaign, called the sugar tax an "important victory" for children's health which will encourage people to choose healthier drinks, and send a wider message about cutting down on sugar for consumers and businesses.

But he added: "On its own, a sugary drinks tax won’t solve the UK’s childhood obesity crisis, which is why it needs to be coupled with robust restrictions on unhealthy food marketing online and across all forms of media, including a 9pm watershed for TV advertising of junk food, alongside a series of other measures on reformulation, labelling and the provision of healthier, more sustainable food in our communities."

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said the tax was "a step forward but only one very small step."

"What we need this tax to create is differential prices for sugary drinks compared to those that are diet versions with limited calories so that the price differential helps the consumer change his or her behaviour."