IT’S CAFFEINE, NOT THE SWEETENER, THAT GETS PEOPLE HOOKED...

SIRIN KALE spent 27 years ‘addicted’ to Diet Coke. At one stage, the 32-year-old journalist from London was glugging up to seven cans a day, spending roughly £500 a year on her habit. Each morning she’d ‘pad to the kitchen’ for a swig before starting her day.

‘I’d get anxious if I didn’t have any in the fridge as bedtime approached, and run to the shop in the middle of the night to ensure there was a cold can waiting for me in the morning,’ she told The Guardian last year.

‘I recently spent a year on prescription medication for a stomach condition that was almost certainly triggered by my over-consumption of Diet Coke.’

When she attempted to quit last January, she was surprised at how tough it was to kick the habit. The first week brought agonising headaches, eased only by a sip of Diet Coke. Eventually, hypnotherapy worked.

Sirin, pictured above, says: ‘Though I still think about Diet Coke, it doesn’t consume my thoughts like it used to. I am not constantly monitoring how many cans I have in the fridge.’

Sirin’s story appears to offer proof that diet drinks – and the super-sweet artificial sweeteners that they’re loaded with – can be addictive. But most experts say that physical addiction to sugar or sweet food, similar to those to a drug or alcohol, isn’t possible.

‘In order for a substance to be physically addictive, you have to experience withdrawal symptoms or a “come down” when you stop having it,’ says psychologist Kimberley Wilson.

The official definition of addiction also requires the person to have cravings for the substance that impact their ability to function normally – which is yet to be proven for sweet foods.

In Sirin’s case, the unpleasant physical symptoms can be explained by withdrawal from caffeine. A can of Diet Coke contains the same amount as two-thirds of an espresso.

Research has shown that sugar can light up the brain’s pleasure centres. ‘We do have an in-built preference for sweet foods because they are high in calories,’ says Wilson, who specialises in eating behaviours.

‘When we eat sugar, levels of a stress hormone called cortisol get suppressed. So it is entirely feasible that people feel real stress relief when they eat or drink something sweet. Over time, it can become a habit.’