Hardness (difficulty of chewing) of the habitual diet in relation to body mass index and waist circumference in free-living Japanese women aged 18–22 y

Abstract

Background: Animal studies suggest the beneficial effect of hardness of diet on body weight and adiposity. No human studies have examined hardness of diet in relation to obesity. Objective: We examined cross-sectional associations of hardness of the habitual diet with body mass index (BMI; in kg/m 2 ) and waist circumference in free-living humans. Design: Subjects were 454 female Japanese dietetic students aged 18 -22 y. Dietary hardness was assessed as an estimate of masticatory muscle activity for the habitual diet (ie, the difficulty of chewing the food). The consumption of a total of 107 foods was estimated by means of a self-administered, comprehensive diet history questionnaire, and masticatory muscle activity during the ingestion of these foods was estimated according to published equations. Waist circumference was measured at the level of the umbilicus. Results: Mean BMI was 21.4 (95% CI: 21.1, 21.6), and mean waist circumference was 73.6 (72.9, 74.3) cm. Mean dietary hardness was 178 (175, 181) mV ⅐ s/1000 kcal. Dietary hardness was not significantly associated with BMI. However, it was negatively associated with waist circumference (P for trend ҃ 0.005). This association remained after adjustment not only for potential confounding factors (P for trend ҃ 0.028) but also for BMI (P for trend ҃ 0.002). Conclusions: Whereas no association between dietary hardness and BMI was seen, increasing dietary hardness was associated with lower waist circumference even after adjustment for BMI in freeliving young Japanese women. This finding could make innovative contributions to the literature and raise issues for future studies regarding diet and obesity.Am J Clin Nutr 2007;86:206 -13. KEY WORDSHardness of diet, body mass index, waist circumference, Japanese, women, diet history questionnaire, epidemiology

Differences in eating behaviors and masticatory performances by gender and obesity status

“…In the present study, the higher chewing power is related to the lower score of disinhibition in both non-obese and pre-obese participants. This may be related to the cross sectional observations reported that greater dietary hardness was associated with healthier dietary patterns, including lower energy and fat and higher protein and dietary fiber and associated with lower waist circumference in young adults [35]. Further study needs to confirm whether the activation of chewing muscle can stimulate the neuronal or cognitive inhibition of impulse eating and its efficacy against obesity.…”

Interleukin-6 Maintains Glucose Homeostasis to Support Strenuous Masseter Muscle Activity in Mice

“…We speculate that in such conditions, involving unusually high levels of masseter muscle activity, IL-6 may be produced and function as a defense mechanism to maintain glucose homeostasis. Soft-food dietary habits are now seen as a health problem, and the importance of hard food is being re-evaluated (Oka et al 2003;Suzuki et al 2005;Murakami et al 2007). Possibly, IL-6 should be considered to be an emergency signal and/or as a factor that allows MM to sustain abnormally high levels of activity.…”

Involvement of apoptosis and proliferation of acinar cells in atrophy of rat parotid glands induced by liquid diet

“…Although modern diets feature soft foods which do not require extensive mastication (Murakami et al 2007), an easily chewable diet is thought to have unfavorable effects on the craniofacial region (Hanihara et al 1981;Varrela 1992). Many experimental studies using laboratory animals have investigated these effects; influence of liquid diet has been confirmed in the craniofacial skeleton (Ito et al 1988;Yamamoto 1996) and masseter muscles (Maeda et al 1990; Kitagawa et al 2004).…”