Daniel M. Keller, PhD

September 13, 2011

September 13, 2011 (Lisbon, Portugal) — Thorough chewing stimulates the release of 2 intestinal peptides that reduce appetite and food intake in obese individuals, Masaaki Eto, MD, professor of clinical pharmacology and medicine at Ohu University in Koriyama, Japan, told delegates here at the European Association for the Study of Diabetes (EASD) 47th Annual Meeting.

In a study of obese nondiabetic individuals, thorough chewing stimulated postprandial increases of plasma glucagon-like peptide (GLP)-1 and peptide YY (PYY), both of which are secreted by intestinal L cells.

Dr. Eto said the study is the first to explore this effect in obese subjects. At last year's EASD meeting, he presented a similar study, but in 22 normal-weight adults.

GLP-1 reduces food intake and stimulates glucose-dependent insulin secretion. The 2 hormones have been implicated in the control of plasma glucose, triglyceride levels, and body weight. Plasma levels of both hormones rise after a meal in normal individuals, as does plasma insulin; plasma glucose remains relatively constant.

For this study, the investigators enrolled 9 subjects (5 male) with a mean age of 41 years. Mean body mass index (BMI) was 27.2 ± 0.4 kg/m2; in Japan, a BMI above 25 kg/m2 is considered obese. Mean fasting plasma glucose level was 99 ± 2 mg/dL, and mean blood pressure was 124/77 mm Hg.

After a 12-hour fast, subjects consumed a test meal in the early morning over a 20-minute period, chewing each mouthful 5 times. On another day, they chewed 30 times. The meal consisted of bread, margarine, a boiled egg, steamed vegetables, a banana, and milk (for a total of 630 kcal). Plasma levels of GLP-1 and PYY were measured before and 1 hour after the meal.

Dr. Eto reported that the postprandial plasma levels of both hormones were statistically significantly higher after chewing 30 times than after chewing 5 times (P < .01 for both). In addition, plasma GLP-1 levels were significantly higher after the meal than before it for both chewing regimens. He suggested that thorough chewing of food might have a clinically meaningful effect in controlling body weight in obese individuals.

Postprandial insulin levels rose to the same degree with both chewing regimens, and were approximately the same as in nonobese individuals.

Chewing Effects on Postprandial Rises in GLP-1 and PYY (Mean Levels)

Chewing Preprandial Postprandial
5 times 4.6 pmol/L 16.9 pmol/L
30 times 5.1 pmol/L 29.3 pmol/L*
Peptide YY    
5 times 35.8 pg/mL 41.3 pg/mL
30 times 35.7 pg/mL 65.9 pg/mL*
*P < .01 vs 5 times postprandial value

During a question period, session moderator Leszek Czupryniak, MD, PhD, from the Department of Diabetology and Internal Medicine at the Medical University of Lodz in Poland, asked Dr. Eto why he had chosen 30 times as the target number for chewing.

"In [Japan], 30 times chewing is recommended by the government to prevent obesity," Dr. Eto replied, raising a round of laughter from the audience. "Increased incidence of obesity is a very, very [big] problem, so since the old days in my country, 30 times chewing was recommended."

Dr. Czupryniak said that in Poland, "grandmothers always told growing children to eat slowly and to chew a lot, but they never gave any number of how many times to chew, so thanks for this advice."

Many audience members asked Dr. Eto if he had considered whether the mechanical act of chewing could stimulate the release of intestinal peptides. Although it is not possible to say definitively from this study, he said he now believes that well-chewed food probably acts in the intestine to better effect the release of the peptides.

Dr. Czupryniak told Medscape Medical News that "what is interesting here is that if you eat something slowly and chew it slowly, the rate of absorption is much slower, and actually, the meal becomes longer. That probably changes the way any hormones are secreted."

Nowadays, "we have instant products and we can eat a lot within 5 minutes, and that's probably wrong," he said.

In his view, the study was probably the most interesting one in the session for the audience because it was about everyday behavior and what dieticians generally recommend to obese individuals "because then you will feel full sooner, and perhaps you will not have to finish your meal."

Dr. Czupryniak suggested that future studies should investigate people with type 2 diabetes, "or even better, with [impaired glucose tolerance].... We have hardly any intervention for people with glucose intolerance, apart from increased physical exercise and dietary limitations, which are very difficult to follow." He also advised doing another study with longer-term follow-up, such as 1 month as opposed to a single meal, to see if it is at all feasible to expect people to follow the recommendation in the long term.

"It's interesting because it's a simple intervention," he said, but compliance might poor unless "you're an old-age, retired pensioner," and not someone with a rushed lifestyle.

This study received no commercial funding. Dr. Eto and Dr. Czupryniak have disclosed no relevant financial relationships.

European Association for the Study of Diabetes (EASD) 47th Annual Meeting: Abstract 17. Presented September 13, 2011.


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