Poorer inhibitory control was related to greater food intake across meals varying in portion size: A randomized crossover trial

Individuals eat more food when larger portions are served, and this portion size effect could be influenced by inhibitory control (the ability to suppress an automatic response). Inhibitory control may also relate to obesogenic meal behaviors such as eating faster, taking larger bites, and frequent switching between meal components (such as bites of food and sips of water). In a randomized crossover design, 44 adults ate lunch four times in the laboratory. Lunch consisted of a pasta dish that was varied in portion size (400, 500, 600, or 700 g) along with 700 g of water. Meals were video-recorded to assess meal duration and bite and sip counts, which were used to determine mean eating rate (g/min), mean bite size (g/bite), and number of switches between bites and sips. Participants completed a food-specific stop-signal task, which was used to calculate Stop-Signal Reaction Time (SSRT). Across participants, SSRT values ranged from 143 to 306 msec, where greater SSRT indicates poorer inhibitory control. As expected, serving larger portions increased meal intake (p < 0.0001); compared to the smallest portion, intake of the largest increased by 121 ± 17 g (mean ± SEM). SSRT did not moderate the portion size effect (p = 0.34), but individuals with poorer inhibitory control ate more across all meals: 24 ± 11 g for each one SD unit increase in SSRT (p = 0.035). SSRT was not related to eating rate or bite size (both p > 0.13), but poorer inhibitory control predicted greater switching between bites and sips, such that 1.5 ± 0.7 more switches were made during meals for each one SD unit increase in SSRT (p = 0.03). These findings indicate that inhibitory control can contribute to overconsumption across meals varying in portion size, potentially in part by promoting switching behavior.

Factors associated with eating rate: a systematic review and narrative synthesis informed by socio-ecological model

Accumulating evidence shows associations between rapid eating and overweight. Modifying eating rate might be a potential weight management strategy without imposing additional dietary restrictions. A comprehensive understanding of factors associated with eating speed will help with designing effective interventions. The aim of this review was to synthesise the current state of knowledge on the factors associated with eating rate. The socio-ecological model (SEM) was utilised to scaffold the identified factors. A comprehensive literature search of eleven databases was conducted to identify factors associated with eating rate. The 104 studies that met the inclusion criteria were heterogeneous in design and methods of eating rate measurement. We identified thirty-nine factors that were independently linked to eating speed and mapped them onto the individual, social and environmental levels of the SEM. The majority of the reported factors pertained to the individual characteristics (n = 20) including demographics, cognitive/psychological factors and habitual food oral processing behaviours. Social factors (n = 11) included eating companions, social and cultural norms, and family structure. Environmental factors (n = 8) included food texture and presentation, methods of consumption or background sounds. Measures of body weight, food form and characteristics, food oral processing behaviours and gender, age and ethnicity were the most researched and consistent factors associated with eating rate. A number of other novel and underresearched factors emerged, but these require replication and further research. We highlight directions for further research in this space and potential evidence-based candidates for interventions targeting eating rate.

Eating rate and bite size were related to food intake across meals varying in portion size: A randomized crossover trial in adults

Serving larger portions leads to increased food intake, but behavioral factors that influence the magnitude of this portion size effect have not been well characterized. We investigated whether measures of eating microstructure such as eating rate and bite size moderated the portion size effect. We also explored how sensory-specific satiety (SSS; the relative hedonic decline of a food as it is eaten) was affected by eating microstructure and larger portions. In a randomized crossover design, 44 adults aged 18-68 y (66% women; 46% with overweight and obesity) ate lunch in the laboratory once a week for 4 weeks. The meal consisted of pasta that was varied in portion size (400, 500, 600, or 700 g) and 700 g of water. Meals were video-recorded to assess bite count and meal duration, which were used to calculate mean eating rate (g/min) and mean bite size (g/bite). At each meal participants also completed an assessment of SSS. The results showed that as larger portions were served, meal intake increased in a curvilinear manner (p < 0.0001). Measures of eating microstructure did not moderate the portion size effect but were related to intake across all portions; faster eating rate, larger bite size, higher bite count, and longer meal duration were associated with greater consumption at all meals (all p < 0.0001). SSS was not influenced by any measure of eating microstructure or by portion size (all p > 0.10). In summary, the portion size effect was not moderated by eating microstructure, but relatively faster eating rates and larger bite sizes at meals, along with large portions, combined to increase food intake.