Abstract
Objectives
Individuals eat more when served larger portions, and this may be influenced by eating-related microstructural behaviors. In a controlled study, we explored whether microstructural components of eating such as eating rate, bite size, bite count, and meal duration influenced the portion size effect.
Methods
In a randomized crossover design, 44 adults aged 18 to 68 y (66% women; 45% with overweight or obesity) ate lunch in the laboratory once a week for four weeks. The meal consisted of a single dish of pasta (1.4 kcal/g) that was varied in portion size (400,500, 600, or 700 g) along with ∼700 g of water. Intake was assessed by weighing items before and after the meal. To characterize eating microstructure, meals were video-recorded to assess bite counts and meal duration, which were used to calculate mean eating rate (g/min) and mean bite size (g/bite). The influence of eating microstructure on the portion size effect was analyzed by random coefficients models.
Results
As larger portions were served, meal intake increased in a curvilinear manner (P < 0.0001). Compared to the smallest portion, intake of the largest portion increased by a mean (±SEM) of 123 ± 16 g (43%). As portions were increased, there were similar increases in bite count (35%) and meal duration (38%; both P < 0.0001), but only small increases in mean bite size (8%; P = 0.019) and no significant change in eating rate (P = 0.92). Measures of eating microstructure did not moderate the portion size effect but did have main effects on intake across all portions. Individuals ate more at the meal when they ate faster, took larger bites, took more bites, or ate for longer (all P < 0.0001). Body mass index did not influence eating microstructure or the strength of the portion size effect but had a modest negative effect on intake across all meals (−5.9 ± 2.7 g/unit increase in BMI; P = 0.046).
Conclusions
Eating-related microstructural behaviors influenced meal intake across portions, but did not moderate the effect of portion size on intake. Individuals who ate faster and took larger bites ate more across all portions, possibly as a result of reduced oro-sensory exposure, which can delay meal termination. Targeted interventions to alter components of eating microstructure have the potential as strategies to reduce overconsumption.
Funding Sources
NIDDK, Jenny Craig.
Mechanisms behind the portion size effect-visibility and bite size