Do sweeteners make people put on weight?

Consuming low-calorie drinks may increase the risk of putting on weight, according to media reports.

US researchers believe that people who choose diet drinks containing artificial sweeteners tend to over-compensate and consume more calories than those who do not choose diet drinks.

Researchers found that rats fed on yoghurt sweetened with the artificial sweetener saccharine consumed more calories and gained more weight than rats that were given yoghurt sweetened with glucose.

They propose that by breaking the connection between a sweet sensation and high-calorie food, the use of saccharine changes the body's ability to regulate how many calories it consumes.

What is the research?
The reports are based on a US study that tested the theory that artificial sweeteners could lead to increased body weight and obesity by interfering with the body's regulation of calories.

The study involved 15 adult male rats, weighing 300-350g, randomly assigned to receive either yoghurt sweetened with glucose or yoghurt sweetened with the artificial calorie-free sweetener saccharine.

Over the five-week study, each rat was fed 30g of yoghurt daily for six days a week. On the seventh day, the rats were given just rat feed and water.

The rats were weighed daily and were measured for changes in core body temperature throughout the five weeks.

At the end of the study, body composition was measured using X-ray absorptiometry.

The researchers found that rats fed yoghurt with saccharine consumed 5g more yoghurt a week than rats fed yoghurt with glucose.

At the end of the study, the saccharine-fed mice were 15-20g heavier than those given the sugary yoghurt. Body fat was also 8 per cent higher in rats fed the artificial sweetener than in rats fed sugar.

Rats that were fed saccharine showed a smaller rise in core body temperature after eating a meal than the rats that where fed glucose.

This indicates that the link between sweetness and high calorie food may have been blunted, leading to over eating, say the researchers.

What do the researchers say?
Lead researcher Dr Susan Swithers, from the ingestive behavioural research centre at Purdue University, Indiana, said: 'Data indicates that consuming food sweetened with zero-calorie saccharine can lead to greater body weight gain and adiposity than consuming the same food sweetened with a higher-calorie sugar.'

This is because sweet food indicates to the body that a lot of calories is about to be consumed, she explained.

'Ingestive and digestive reflexes gear up for that intake but when false sweetness is not followed by lots of calories, the system gets confused,' Dr Swithers said.

'Thus people may eat more or expand less energy than they otherwise would.'

Other artificial sweeteners such as aspartame, sucralose and acesulfame K could also have similar effects, she added.

What do other researchers say?
Bridget Aisbitt, a nutritional scientist at the British Nutrition Foundation, said: 'This is interesting research but it is important to remember that it was performed in rats and not humans.

'Studies have been carried out in humans that have not backed up the claims of this latest study'.

'Humans are unable to differentiate between sugar and artificial sweeteners accurately enough to influence calorie intake.'

There is no need to change guidance over artificial sweeteners, she said adding that they can help to reduce weight as part of a balanced diet.

Behavioural Neuroscience Online 2008

Informing patients

  • Consuming artificial sweeteners instead of sugar could lead to weight gain.
  • Rats fed yoghurt sweetened with the artificial sweetener saccharine gained more weight than rats fed yoghurt sweetened with glucose.
  • Studies performed in humans have shown that artificial sweeteners can help weight loss.

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