Have you got the fat gene?

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We've all heard it before but obesity is on the rise - there are around 1.6 billion obese people in the world and unless we all do something to stay fit and healthy now, that number will just keep growing and we'll all face serious health problems in the future.

So, wouldn't it be nice if we could all blame a rogue gene for our expanding waistlines. Unfortunately, scientists say it's not that straightforward. There are actually several genes that may lead to obesity, or at least to the body storing more fat than normal.

Here we look at three fat genes:

Sar1b

This was found in people with some rare diseases and scientists discovered that Sar1b, which is needed by your body to absorb fat properly, doesn't work. This means you end up absorbing more fat from food than other people.

Leptin

There's a newly-discovered substance called leptin, which plays a role in human appetite - so if you don't produce enough leptin then you may feel more hungry than others and end up eating more. What's more, scientist found a link between leptin and a resistance to insulin, which can lead to Type 2 diabetes

MC4R

There's a sequence of genes called MC4R which are carried by nearly half the population of the world. A study found that MC4R influences how much we eat and how much energy we use and save. This sequence of genes is more common in Indian Asians, which scientists think could explain the unusually high levels of obesity and insulin resistance among this group. They are expected to account for 40% of global heart disease by 2020.

By Louise O'Connell