It's no secret, portion sizes have been increasing for the last 50 years and we have become habituated to a new SUPER-SIZED normal.
Evolutionarily, we all want the best deal. Deep down we crave the cheapest most-delicious calorie-rich options…in our current environment that generally means nutrient-poor hyper-palatable snacks (AKA chips) or fast food.
When we are surrounded by larger packages, larger servings, and more variety of these items…we eat more.
“Larger than necessary meals promote passive overconsumption, and research has demonstrated a positive association between the portion size served and the amount consumed, though NO association between ratings of hunger and satiety and the portion size served was found.”
-Poelman et al., 2014 
More calories without more fullness! Eeeeek!
On the flip side, when people are provided with pre-portioned servings they seem to reduce their food intake without making up for it later.
What?!? Potentially less calories for the same fullness!
And the really REALLY cool aspect of switching to properly portioned whole food based meals is that over time we may actually be able to rewire a NEW NEW normal!!
1. Poelman, M.P., et al., Behavioural strategies to control the amount of food selected and consumed. Appetite, 2014. 72: p. 156-65.
2. Robinson, E. and I. Kersbergen, Portion size and later food intake: evidence on the "normalizing" effect of reducing food portion sizes. Am J Clin Nutr, 2018. 107(4): p. 640-646.