Dieters who regularly add artificial sweetener to their favourite beverage or consume diet food and drinks containing sucralose could end up feeling hungrier and eat 30 per cent more than usual, according to a new study in animals revealing the unintended consequence of using fake sugar.
Australian research, published in Cell Metabolism today, finds that the artificial sweetener called sucralose could make us eat more and possibly put on weight because sucralose affects a system in the brain that senses and balances the sweetness and energy content of what we consume.
The study on fruit flies, co-led by the University of Sydney’s Charles Perkins Centre and the Garvan Institute of Medical Research, shows the brain’s reward centres integrates sweet sensations with energy content. So when the brain perceives that we are getting a certain amount of sweetness – achieved by consuming artificial sweeteners in our food and drinks – it expects to receive a related amount of energy.
But when sucralose fails to provide the equated number of kilojoules, the brain’s ‘sweetness versus energy’ equation falls out of balance. The brain then recalibrates and increases total kilojoules consumed.
"There’s a gauge that switches on in the brain and makes it say ‘I need more calories’.”
“We didn’t see an immediate effect when we added extra sweetness to the animals’ diet using artificial sweeteners but chronically over time, around five days, the animals became extra hungry and ate more,” says lead researcher Associate Professor Greg Neely from the University of Sydney’s Faculty of Science.
“They ate around 30 per cent more calories [kilojoules] after a chronic exposure to artificial sweeteners.
“So from our experience with fruit flies and mice, if we create an imbalance between the perceived sweetness of food and the actual sweetness of food, then over a long time, it changes the brain. There’s a gauge that switches on in the brain and makes it say ‘I need more calories’.”
A/Prof Neely explains that the fruit flies were given twice a much fake sugar than the amount of real sugar they would normally consume day-to-day.
He adds that after five days of treating the animals with an artificially sweetened diet, real sugar was re-introduced.
When this happened, the animal’s taste perceptions changed as they became more sensitive to real sugar.
“We also believe that’s why they started eating more,” he says.
“This phenomenon reverses after three days so if the fruit flies ate artificial sweetener for five days, on day eight their body would return to normal. The good news is that after the animals stopped consuming artificial sweetener, there was no permanent damage or effect and no change to life span.”
The researchers also found artificial sweeteners promoted hyperactivity, insomnia and decreased sleep quality – behaviours consistent with a mild starvation or fasting state.
The artificial sweetener, sucralose is often added to add sweetness to food that requires baking, sugary drinks or products with a longer shelf life, without adding kilojoules.
The study, the first to identify how artificial sweeteners might stimulate appetite, raises questions over the use of sucralose as a dieting tool to treat obesity and promote weight loss.
“These findings further reinforce the idea that ‘sugar-free’ varieties of processed food and drink may not be as inert as we anticipated,” says study co-author, Professor Herbert Herzog from the Garvan Institute.
“Artificial sweeteners can actually change how animals perceive the sweetness of their food, with a discrepancy between sweetness and energy levels prompting an increase in caloric consumption.”
“Sometimes low sugar jam or low sugar brownies have sucralose in them and it’s hard to see that they contain artificial sweetener."
A/Prof Neely also cautions constant dieters about the possible dangers of eating artificial sweetener, hidden in ‘low sugar’ products like diet soft drinks, over the long-term.
“Sometimes low sugar jam or low sugar brownies have sucralose in them and it’s hard to see that they contain artificial sweetener,” says A/Prof Neely.
“I personally believe that everything is fine in moderation but with people drinking 10 litres of diet soft drink, that could have an effect on their brain.”
The study’s results, while proven in animals, have not yet been tested on humans. Yet A/Prof Neely says he believes the main theme of study’s findings should translate to people: “excessive artificial sweetening of the diet could have unintended consequences”.