Chewing, Eating Rate, and Weight Status in Children

Objectives Primary Objective: To examine whether there is an association between the eating duration of a standard meal and weight status (as BMI Z-score) among children aged 6-11.

Secondary Objectives:

1. To determine whether there is an association between the number of chews of a standard meal and the weight status of children aged 6-11.
2. To examine whether there is an association between chewing rate (total weight of food consumed/total eating time) during a standard meal and daily energy intake among children.
3. To examine whether there is an association between chewing rate during a standard meal and body composition among children.
4. To examine whether there is an association between the eating duration of a standard meal and the reported satiety level of children aged 6-11.
5. To examine whether there is an association between the eating duration of a standard meal and total daily energy intake.
6. To assess whether the associations between chewing behaviors, eating characteristics, and dietary intake differ between boys and girls.
7. To assess the relationship between chewing-related behaviors and salivary ghrelin responses before and after meal consumption.

Study Design and Methodology Study Design: This doctoral project is a randomized, crossover, laboratory-based experimental study conducted among healthy children aged 6-11 years. Participants will attend multiple assessment sessions during which they will consume standardized isocaloric test meals differing only in food texture and chewability characteristics. The crossover design enables within-subject comparison of oral processing responses under different meal conditions while reducing inter-individual variability. All experimental sessions will be conducted under standardized laboratory conditions.

Study Population: The study will include approximately 70 children aged 6-11 years, including those with normal weight and those with obesity, according to World Health Organization BMI-for-age z-score criteria. Children with medical conditions or dietary restrictions that may affect eating behavior, appetite regulation, or food consumption will be excluded. The selected age range represents a critical developmental stage during which eating patterns, satiety regulation, and obesity-related behaviors may still be influenced through behavioral and nutritional interventions.

Primary Outcomes: Primary oral processing variables will include: Chewing duration; Number of chews; Eating duration; Eating rate; Amount of food consumed.

Secondary Outcomes:

1. Satiety Assessment: Subjective hunger and satiety responses will be evaluated using validated Visual Analog Scale (VAS) ratings before the meal, immediately after the meal, and during the postprandial period.

Hormonal Assessment: Salivary ghrelin concentrations will be measured before and after test meals using standardized saliva collection and biochemical analysis procedures. Ghrelin was selected due to its established role in appetite regulation and meal-related hunger signaling.

Methods Study Procedure: Participants will consume standardized test meals developed to differ in texture and chewability while maintaining comparable caloric and macronutrient composition. Meals will include foods categorized according to oral processing difficulty and chewing demands. During meal consumption, oral processing behaviors will be objectively assessed using synchronized behavioral and physiological measurement systems. To account for familial and shared environmental influences on eating behavior, at least one parent will undergo a parallel assessment, conducted separately from the participating child.

Meal consumption will be recorded using panoramic video cameras, and chewing-related behaviors will be coded by independent evaluators. In addition, meals will be administered using the Universal Eating Monitor (UEM), a concealed scale-based system that continuously records food intake throughout the meal and enables high-resolution assessment of eating microstructure.

Anthropometric and Body Composition Assessment: Children and parents will undergo standardized measurements of: Weight and height; BMI-for-age z-score/Parental BMI; Body composition using InBody 770; Upper-body muscle strength using JAMAR dynamometry.

Dietary and Behavioral Questionnaires: Additional assessments will include: 24-hour dietary recalls; Physical activity questionnaires; Sociodemographic questionnaire; Children's Eating Behavior Questionnaire (CEBQ) (children only); AUT-EAT questionnaire (to assess eating behaviors and challenges specifically in children on the Autism Spectrum) (children only); parental eating behaviors questionnaire. Parents weight, height and eating behaviors will be recorded during one meal session.

Statistical Analysis: Statistical analyses will be conducted using IBM SPSS Statistics, version 31.0. Descriptive statistics will summarize participant characteristics overall and by weight-status group. Continuous variables will be assessed for normality and presented as means ± SD or medians and interquartile ranges, as appropriate; categorical variables will be presented as frequencies and percentages. Group comparisons will be performed using t tests, Mann-Whitney U tests, chi-square tests, or Fisher's exact tests, as appropriate.

Given the randomized crossover design, primary analyses will use linear mixed-effects models to account for repeated measurements within participants across meal conditions. Models will include participant as a random effect and meal texture, weight status or BMI-for-age z-score, visit order, and relevant covariates, including age, sex, and socioeconomic characteristics, as fixed effects. Interaction terms will be used to examine whether responses to soft versus hard meals differ by weight status or sex.

Primary behavioral outcomes, including eating duration, chewing duration, number of chews, eating rate, and food consumed, will be analyzed in relation to BMI-for-age z-score, body composition, satiety ratings, ghrelin responses, and total daily energy intake. Satiety and salivary ghrelin changes will be examined using repeated-measures models and pre-to-post meal change scores. Parent-child associations in eating behaviors and anthropometric measures will be explored using correlation and regression analyses.

Exploratory mediation analyses will assess whether satiety and ghrelin responses partially explain associations between oral processing behaviors and weight-related outcomes. Model assumptions will be evaluated, and sensitivity analyses will be conducted for missing or extreme values. Statistical significance will be set at p \< 0.05, with effect sizes and 95% confidence intervals reported alongside p values.