Obesity blamed on sweet tooth lasting into our adult lives

OBESE people may become fat because they never lose their childhood sweet tooth.

Normally, as young people reach adulthood, their preference for sweet foods decline.

But a study suggests that this desire for sugar does not fade for obese people, so they continue to seek out sweet foods and drinks.

Experts at Washington University in the US think that the brain’s ‘reward system’ may operate differently among the obese.

For people of normal weight, a taste for sugar is linked to a lower number of dopamine receptors in the brain.

Dopamine receptors receive the sensation of a sweet flavour and convert it into a pleasurable feeling.

However, in overweight people, a sweet tooth is linked to a higher number of the receptors in the brain.

The scientists suspect this is because being overweight changes the balance of hormones.

Researcher Professor Yanina Pepino said: ‘As we age, we have fewer dopamine receptors in a brain structure, called the striatum, that is critical to the reward system. We find that both younger age and fewer dopamine receptors are associated with a higher preference for sweets in those of normal weight. However, in people with obesity, that was not the case in our study.’ The team, whose work is published in the Diabetes medical journal, studied 20 people of a healthy weight and compared them with 24 people considered obese.

The participants, each aged between 20 and 40, received drinks containing different levels of sugar to determine the degrees of sweetness they preferred.

The researchers then scanned the brains of the volunteers.

Co-author Professor Tamara Hershey said: ‘The general trend in people of normal weight was that having fewer dopamine receptors was associated with a higher preference for sweets.’

The scientists suspect that insulin resistance, a change in hormones which is often a consequence of obesity, and is linked to diabetes, could be behind the change in obese people’s brain structure.