This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
About a century ago, a new craze gripped the country's health conscious: mastication. Chewing each bite of food precisely 32 times would help people control how much food they consumed—turning them from gluttons to epicureans—according to the early 20th-century dietician Horace Fletcher.
Among his many ardent adherents the tactic became known as "Fletcherizing." And Fletcher, in turn, has gone down in dietary history as "The Great Masticator," with the purported catch phrase: "nature shall castigate those who don't masticate."
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The theory, almost quaint in its specificity, soon fell out of popularity to be replaced by more familiar mid-20th-century forms of calorie-limiting diets.
But a recent study out of China provides a new look at the role that chewing might have in helping our bodies regulate the amount of food we take in—without having to consult calorie labels.
Jie Li of the School of Public Health at Harbin Medical University and colleagues found that both healthy-weight and obese men consumed fewer calories (about 12 percent less) at an unlimited half-hour meal when they chewed their food more.
Wolfing down a whole meal is often considered poor form, and previous research has linked slower eating habits with a healthier weight. The common wisdom is that eating more slowly gives the body more time to "feel full."
But as logical as it is that slower eating—coupled with or aided by more chewing—might be linked to consuming less, the specifics have yet to be fully worked out. One theory is that breaking food down in the mouth via more chewing allows the body easier access to nutrients, which would allow less consumption for the same nutritional benefit. But how does the body know when it should stop stuffing its face?
"Mastication apparently plays a role in the gut hormone profile, which consequently influences energy intake," the scientists wrote in their paper, published in July in the American Journal of Clinical Nutrition. Hunger is largely controlled by hormonal signals, including that from ghrelin, which spurs the feeling of hunger. The team found that when study participants chewed more, their ghrelin levels were consistently lower post-mealtime. It might be that the longer the body senses food in the mouth, the more ghrelin is released.
The study centered on a series of experimental breakfasts. Young men recruited for the study—16 of whom had body mass indexes (BMIs) of 18.5 to 23, which is considered lean for Asian men, and 14 of whom had BMIs of 27.5 or greater, which qualified them as obese for their demographic, sat down each morning to 300 grams of pork pie (a standard Chinese breakfast dish), with an option for additional servings. Researchers videotaped each subject eating and subsequently counted how many times they chomped down on each bite. The range across subjects was roughly 15 to 40 chews. During subsequent breakfasts, each subject was told to chew their bites either15 or 40 times.
Left to their own devices, all of the men had roughly the same preferred bite size (about 10 grams), but obese men ate each gram of food more quickly and with fewer chews than those who were leaner.
But after breakfasts during which they had to chew each bite 40 times, subjects consumed 11.5 percent fewer calories overall—and had lower concentrations of the hunger-piquing ghrelin hormone in their bloodstream afterward—than after morning meals during which they chewed each bite only 15 times.
So will more mastication help people slim down or keep the pounds from piling on in the first place? The researchers suggest "interventions for improved chewing activity" as a possible means for helping to stem obesity. The new study was too preliminary to tell whether The Great Masticator's historical message could help rein in expanding waistlines for the long term. But the new findings at least give us something to chew on.
Image courtesy of iStockphoto/Lighthaunter