The researchers, led by Martin Yeomans from the University of Sussex, investigated the difference between flavour preferences due to flavour and nutrients of sugar or artificially-sweetened beverages before and after eating, and found that preference for the sucrose sweetened drink increased after eating.
The result may help with the understanding of the proposed link between sweet-flavoured soft drinks and unhealthy diet and weight gain.
Over 300m adults are obese worldwide, according to latest statistics from the WHO and the International Obesity Task Force. About one-quarter of the US adult population is said to be obese, with rates in Western Europe on the rise although not yet at similar levels.
The Sussex-based researchers recruited 60 volunteers (48 women) with an average age of 23.5. Each participant was asked to drink one of three versions of a test drink at home either before or after lunch. The drinks were formulated to be: minimally sweetened (Control; three per cent sucrose, 40 kcal), artificially sweetened (3 per cent sucrose plus acesulphame-K, 40 kcal) and sucrose-sweetened (9.9 per cent sucrose, 132 kcal).
Unilever Research (Colwork, UK) provided the uncarbonated peach-flavoured iced tea test drink in 330 ml identical cans.
It was found that the perceived pleasantness of the sucrose-sweetened drink increased after eating, while both the artificially and control sweetened drinks did not result in significant changes in terms of perceived pleasantness.
The volunteers were subsequently 'trained' to like sweet flavours, and re-testing using the same drinks and conditions resulted in significant pleasantness ranking for the sucrose-sweetened drink both before and after eating.
A significant increase was observed in the perceived pleasantness after eating for the trained tasters of the artificially-sweetened beverage, while pleasantness for the control decreased by over 30 per cent for the control drink.
"Overall increases in pleasantness for the flavour in participants who consumed the sucrose drink when sated or the [artificially-sweetened] drink independent of hunger state, suggest that flavour-flavour learning occurred," wrote lead author Sirous Mobini in the journal Appetite (doi: 10.1016/j.appet.2006.05.017).
Flavour-flavour learning (FFL) refers to liking of a particular flavour based on already liking a similar flavour.
"Liking for the flavour of both sugar-sweetened or artificially sweetened drinks could develop through FFL since in general we express liking for sweet tastes," said the researchers.
The results have implications in the struggle against obesity with many soft drinks being targeted as a major reason for the growing epidemic of obesity because of concerns over the sugar content. Such claims have already resulted in many public and private institutions removing soft drink vending machines from their halls.
Carbonated drinks manufacturers have of course responded to growing consumer fears with the launch of numerous low calorie alternatives. The level of low calorie penetration in the developed world reflects the changing lifestyle of consumers, reaching 30 per cent in the key North American market, and 18 per cent in the number two volume region, West Europe.
Global drinks consumption rose by 2.5 per cent during 2005, according to globaldrinks.com, Zenith International's online database.
The total volume consumed was 1.47 million million (trillion) litres, equivalent to 227 litres per person.
The rise in beverage sales was driven mainly by soft drinks, whose worldwide consumption increased by 3.9 per cent to 499 billion litres, equal to 77 litres per person.
But in the context of growing concern about obesity levels and greater public interest in health, it is interesting to note that the advance of soft drinks was led by better for you categories such as bottled water, fruit drinks and functional drinks.
This trend is expected to continue, with bottled water set to beat carbonated soft drinks by 2009 and still drinks fast approaching the combined volume of dilutables, nectars and fruit juices.