Nutritionists in China found when both lean and obese young men chewed more at a meal, they ingested fewer calories and
had more favourable levels of gut hormones in their blood, lending credence to the old Swedish proverb that says, among other
things, "Eat less, chew more", and "all good things will be yours". You can read about the study by Jie Li and colleagues from
the School of Public Health at Harbin Medical University, in the August issue of the American Journal of Clinical
Li and his team invited 16 lean and 14 obese young men to take part in two studies. In the first study, they observed the differences in chewing habits between the lean and the obese group.
In the second study, the participants were offered the same test meal on two separate occasions. For the first occasion they were asked to chew at a rate of 15 chews per 10-g bite of food, and on the second occasion at a rate of 40 chews per bite. The test meal was a breakfast with a total energy value of 2200 kJ (68% as carbohydrate, 21% as fat, and 11% as protein). The volunteers gave blood samples after each meal so the researchers could measure circulating levels of blood sugar and gut hormones.
The results showed that:
- Despite having a similar bite size as the lean participants, the obese participants ate faster and chewed fewer times per 1 g of food.
- Both obese and lean participants ate 11.9% fewer calories in the meal where they chewed 40 times per bite compared to the meal where they only chewed 15 times per bite.
- In both the lean and the obese participants, chewing 40 times per bite resulted in lower blood levels of ghrelin (a hormone that stimulates appetite) and higher levels of cholecystokinin (CCK, a hormone that signals fulness and tells the stomach to slow down digestion), than chewing 15 times per bite.
"Interventions aimed at improving chewing activity could become a useful tool for combating obesity."
One of the limitations of the study is that the volunteers were all young men, so the findings may not be true for other groups such as women and older people.
Another limitation is that not all calories people ingest comes from food that requires chewing: for example ice cream, sugary and alcoholic drinks, so it is unlikely that chewing more will cause people to reduce their calorie intake by 12%, as the participants did in this study, which was based on one solid food test meal.
However, the researchers do suggest that there is enough evidence here to warrant further investigation about whether changing chewing habits and other eating behaviours can help address the growing obesity problem.
Written by Catharine Paddock, PhD