Weight loss advocates are always talking about how we can lose weight if we watch what we eat. But can we lose weight if we are mindful about how we chew?
Chewing – or mastication – is the first step we take to eat and an important part in the digestion process. Saliva contains digestive enzymes, so the longer that we chew our food, the longer these enzymes have to break it down before it travels to our stomach and into the small intestine.
Celebrity doctor, Dr Xand van Tulleken tests whether chewing can help us to eat less in episode one, series two of The Diet Testers, airing on SBS Thursday 19 April at 9.30pm. To do this, he recruits the help of a research team and adapts a recent study on chewing to fit a sample size of 20 participants.
To make the test scientifically valid and to eliminate variances in gender, the participants selected were all female.
“Even 15 chews sounded, to me, to be quite a lot."
Volunteers were divided into two groups: both groups were served identical quantities of pasta to consume. The participants in group one were required to chew each mouthful of food 15 times. Group two had to chew each mouthful 35 times.
The women in both groups were instructed to eat as much as they wanted until they were full, after which point the amount of food left over would be weighed.
The purpose of designing the study this way was so that researchers could observe which group – on average – ate less food and whether chewing influenced how much was eaten.
“Even 15 chews sounded, to me, to be quite a lot,” says Dr Xand.
Results showed that the participants who chewed their food more felt just as full as those who chewed less, even though they had eaten fewer calories.
Some of the participants in the group which chewed more commented: “it took the taste out of the food” and “it made me eat less just because it was such an effort to get through it”.
The group who chewed each mouthful 15 times consumed 468 calories. Meanwhile, the group who chewed 35 times consumed 342 calories, eating 26 calories less just by chewing their food more.
“That, to me, is amazing,” says Dr Xand, directing his comments at the study’s participants, “that you all had the same food and same quantities and there’s more than a quarter difference”.
“I must say, I did not think chewing was a very important part of life but it’s safe, it’s free and it has no side-effects.
“There is some evidence that it works [to help you eat less]. And some of that evidence I have seen with my own eyes. So I would say why not give it a go?”
But why does chewing – of all things – make us eat less?
A study published in the American Journal of Clinical Nutrition in 2011 also looked at the effect that chewing has on food consumption, drawing a similar conclusion to Dr Xand’s test: chewing makes you eat less.
But the researchers also went one step further to ask why, testing the theory that chewing may impact energy intake and gut hormones.
The research conducted involved young males – 16 who were lean and 14 who were obese. All of the study participants were given a test meal 2200 kilojoules, which was consumed during two different sessions: one session tested 15 chews per bite and the other examined 40 chews per bite. Each bite of food weighed 10 grams.
“I must say, I did not think chewing was a very important part of life but it’s safe, it’s free and it has no side-effects."
Results showed that compared with lean participants, obese participants had a lower number of chews per one gram of food. However, when subjects chewed their food 40 times, they ingested 11.9 per cent less food compared to when food was chewed 15 times.
Compared with 15 chews, 40 chews resulted in lower energy intake for both obese and lean subjects.
Apparently, this was because chewing more caused levels of ghrelin – a peptide hormone known as the "hunger hormone" – to decrease. A higher postprandial glucagon-like peptide-1 (GLP-1) concentration – a secretion that signals meal termination – also occurred after participants chewed their food more.
“Interventions aimed at improving chewing activity could become a useful tool for combating obesity,” the study concludes.
Another study published in 2014 shows that eating slowly can make you feel fuller faster and it significantly lowers the amount you eat if you have a healthy weight. However, it does not generate the same impact in overweight or obese individuals.
Want to know more about what's behind some of the most popular dieting methods around? Watch series two of 'The Diet Testers', airing on Thursdays at 9.30pm on SBS from 19 April.
Episodes will be available to watch after broadcast on SBS On Demand.