Abstract
Increases in food portion sizes have been identified as a possible contributor to the increased prevalence of obesity in humans. However, little is known about the origin of behavioural tendencies to overeat from larger portion sizes or whether other non-human animals are affected by meal portion size. In the present experimental study, we examined the effect that larger portion sizes have on meal consumption among domesticated dogs (N = 32). Dogs were fed three meals that varied in size on different occasions (150%, 200% and 300% of usual portion size). A repeated measures design was used and food consumption was measured for each meal. Portion size positively affected food consumption, with dogs eating significantly more food as the portion size of meal increased. The effect of portion size on food consumption was also observed when the dogs that finished all available food were excluded from analyses, however not among dogs who did not finish any of the meals. We conclude that the influence larger portions have on food consumption observed in humans is also observed in domesticated dogs. However, it is unclear whether portion size directly biases the amount of food dogs choose to consume, as has been suggested in humans. Further research is now warranted to examine commonalities between human and non-human animal eating behaviour to understand shared behavioural tendencies and their origins.
Highlights
Human energy intake from food is affected by portion size: we eat more when offered a larger portion compared to smaller portions
Dogs tended to eat more from the 300% portion size than the 200% portion size, and the 150%
We investigated the effect of portion size on food consumption in domesticated dogs
Summary
Human energy intake from food is affected by portion size (i.e., the amount of food that is served on a specific eating occasion): we eat more when offered a larger portion compared to smaller portions. This effect known as the ‘portion size effect’, and has reliably been shown across a range of food types and participant groups (Hollands et al, 2015; Zlatevska, Dubelaar, & Holden, 2014). To date, the extent to which domesticated dogs will overeat when served larger portions of food has not been empirically tested and at present we do not know whether, like in humans, portion size biases how much dogs consume during a meal. We hypothesised that voluntary food intake in dogs would be increased when served larger portions of food
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