Sweeteners linked to higher weight gain: Rat study

By Nathan Gray

- Last updated on GMT

Sweeteners linked to higher weight gain: Rat study

Related tags Sucralose

Consumption of non-nutritive sweeteners such as saccharin and aspartame could lead to increases in weight, according to new data in rats.

There is a wealth of evidence to suggest that consumption of foods and beverages containing low, or no, calories can help to battle obesity by reducing the calorific value of products without affecting taste or subsequent feelings of hunger.

However, the new study – published in Appetite​ – examined how consumption of food containing a non-nutritive sweetener (NNS – in the form of saccharin or aspartame) affected the caloric intake and weight gain of rats when compared to consumption of food containing sucrose.

Led by Dr Marcello Casaccia Bertoluci from the Federal University of Rio Grande do Sul, Brazil, the research team found whilst total caloric intake was similar between groups, rats fed saccharin and aspartame had higher levels of weight-gain than those fed sucrose.

“We observed significantly greater weight gain among Wistar rats fed diets supplemented with NNS – whether saccharin or aspartame – compared with sucrose,”​ said the authors.

“It was surprising to find that the NNS were able to induce weight gain without an increase in total caloric intake, suggesting that other mechanisms such as decreased caloric expenditure may occur after NNS use,”​ they added. “We speculate that a decrease in energy expenditure or increase in fluid retention might be involved.”

Study details

Bertoluci and his team fed 29 male Wistar rats a plain yogurt sweetened with either 20% sucrose, 0.3% sodium saccharin or 0.4% aspartame, in addition to chow and water ad libitum, while physical activity was restrained.

The team then measured cumulative body weight gain, total caloric intake, caloric intake of chow and caloric intake of sweetened yogurt for 12 weeks.

According to their analysis, Bertoluci and his colleagues found the addition of either saccharin or aspartame to yogurt resulted in increased weight gain compared to the addition of sucrose, despite total caloric intake being similar between all the groups.

“Although saccharin and aspartame promoted relatively fewer calories from yogurt intake when compared to sucrose, increases in calories from chow intake effectively compensated for decreases in calories from yogurt, in such a way that there was a similar total caloric intake among all groups after the 12-week period of the experiment,”​ said the authors.

“These data are consistent with the hypothesis that animals adjust for calories consumed on one occasion by reducing their caloric intake on subsequent opportunities to eat,”​ they said.

Bertoluci and his team said further studies that address energy expenditure after NNS exposure in rats, in addition to long-term clinical trials to evaluate weight gain increases in humans, are now needed.

Source: Appetite
Volume 60​, Pages 203–207, doi: 10.1016/j.appet.2012.10.009
“Saccharin and aspartame, compared with sucrose, induce greater weight gain in adult Wistar rats, at similar total caloric intake levels”
Authors: Fernanda de Matos Feijó, Cíntia Reis Ballard, Kelly Carraro Foletto, Bruna Aparecida Melo Batista, et al

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Poor design

Posted by John Fry,

There are several inadequacies in the experimental design:-
1) the rats receiving sweeteners derived only 12.6% of their energy from artificially-sweetened yogurt, the rest from a fully-balanced lab chow. The rats receiving sugar derived 24% of their energy from yogurt containing 20% sugar. The "sugar" rats thus received a nutritionally inferior diet compared to the others.
2) There was no "all chow/no sugar" control group.
3) Only 10 rats per group.
4) Unrealistic levels of sweetener used: aspartame was 650% more than would be used in practice, saccharin was 2600% higher than would be allowed in the EU.

This is indeed a difficult area experimentally, and the conclusion is more complex than your story suggests.

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Difficult experiment

Posted by Jurgen Denecke,

Although the rat experiment sounds simpler than working with human test groups, it is still a very difficult experiment. To state that weight gain was higher despite similar total caloric intake may be incorrect, if the quality of the food intake is more suitable for weight gain. One would have to compare glucose with the same amount of starch (a non-sweet glucose polymer) to guarantee identical caloric quantity and similar nutritious quality.
However, I thought it was well established for humans that sweet food sensations in the mouth induce insulin production, leading to lower blood sugar levels, inducing hunger, and leading to further food consumption.

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