Published on 1st May 2017


A recent study has suggested that drinking carbonated drinks, both diet and non-diet, could be making us fat.

Fizzy drinks have long been considered to be a factor in obesity, with both non-diet and diet drinks being implicated. On the one hand, it is generally thought that sugar is the culprit, while with diet drinks it has been proposed that the effect of sweeteners on the brain can stimulate the appetite. What is different about this research, however, is that it has focused on carbonated water, which is an ingredient that is present in both diet and non-diet sodas.

A team of scientists from Birzeit University in Palestine (1) found that over a period of six months, rats given either diet or non-diet carbonated drinks ate more and gained more weight than rats that were given either flat soda or plain water. The rats’ weight gain was associated with increased production of ghrelin, commonly known as the ‘hunger hormone’, which is produced by rats and humans alike, and which would account for the rats’ bigger appetites.

Following these findings, the team then carried out a study on a group of 20 men aged 18-23, looking at the effects of carbonated and flat soda. An hour after a light breakfast, the subjects were given either: tap water; regular degassed (flat) soda; regular carbonated soda; or diet carbonated soda. Blood tests revealed that the men who drank the carbonated soda, whether diet or regular, had higher ghrelin levels afterwards.

Published in Obesity Research and Clinical Practice, the research found that in the case of rats, weight gain was more significant and similar among the rats that drank the fizzy drinks. The slowest weight gain out of all four groups was found in the rats that only drank plain water. Among the human subjects, it was found that ghrelin levels after drinking carbonated drinks were three-folds higher than after drinking flat soda, and six-folds higher than after drinking plain water.

Whilst carbonated drinks alone cannot be blamed for the obesity epidemic we are currently witnessing in the UK and elsewhere, the research does suggest that plain water may be a more reliable option if we are trying to watch our weight.


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