Turns out that the same part of our brain that tells us we're full also triggers sugar cravings.

Researchers say from an evolutionary perspective sugar is rare in nature, so our 'caveman' brains are wired to get it where we can.

The study found that mice who ate until they were full could barely eat any of the second serving of their main meal.

However, the mice ate six times as many calories when they were offered a sugary treat instead,

Researchers found that the brain lit up in an area called the paraventricular thalamus.

A group of appetite and regulating nerve cells called the pro-opiomelanocortin (PMOC) neurons lit up as soon as the mice were given sugar, which enabled their appetite.

Researchers found that not only did the PMOC neurons release signalling molecules to tell the body it was satiated, but they also released a bodily opiate, ß-endorphin.

The opiate pathway was only activated in the rodents’ brains when they were offered sugary food, not additional regular food or fatty food.

In a follow-up experiment on humans, scientists discovered that the same part of the human brain reacted to the sugar as it did in the mice.

Thus, proving that humans really do have “dessert stomachs”.

Senior author of the study from Max Planck Institute for Metabolism Research, Dr Henning Fenselau, said: “Like many people, I find it difficult to say no if there is a very chocolatey and sweet dessert available.

“It can be very hard to resist and, from an evolutionary perspective, that makes sense as sugar provides rapid energy and is hard to find in nature, so our caveman brains are programmed to get it when we can.

Fenslau added that the findings could help in future research into the treatment of obesity.

"There are already drugs that block opiate receptors in the brain, but the weight loss is less than with appetite-suppressant injections," Fenselau noted.

"We believe that a combination with them or with other therapies could be very useful. However, we need to investigate this further."