People who chew their food more take in fewer calories, mainly because more chewing is related to the levels of hormones that regulate appetite, according to a Chinese study.
Chewing food 40 times instead of a typical 15 times caused the study participants to eat nearly 12pc fewer calories, the study, published in the American Journal of Clinical Nutrition, said.
"Compared with lean participants, obese participants had a higher ingestion rate and a lower number of chews per 1g of food," wrote lead researcher Jie Li from Harbin Medical University in China.
"Regardless of status, the subjects ingested 11.9pc less after 40 chews than after 15 chews."
Li's team gave a typical breakfast to 14 obese young men and 16 young men of normal weight to see if there were differences in how they chewed their food.
They also looked to see if chewing more would lead subjects to eat less and would affect the levels of blood sugar or certain hormones that regulate appetite.
Several previous studies have found that eating faster and chewing less are associated with obesity, while others have found no such link.
But in the current study, the team found a connection between the amount of chewing and levels of several hormones that "tell the brain when to begin to eat and when to stop eating".
More chewing was associated with lower blood levels of ghrelin, a hormone that stimulates appetite, as well as higher levels of CCK, a hormone believed to reduce appetite.
These hormones may represent "useful targets for future obesity therapies".
The study said the 12pc calorie reduction for the group who chewed their food 40 times could potentially translate into significant weight loss.
Average people who cut their calorie intake by that much lose nearly 25lb in a year, said Adam Drewnowski, of the University of Washington Centre for Obesity Research.
But since the typical diet includes foods that are not chewed, such as soup, the actual amount of weight one is likely to lose by chewing more is much less, he warned.