The Happy Meal isn't just for kids anymore. According to a study in the "Journal of Experimental Psychology: Applied," when a small incentive is offered with a meal, as is the case with the toys found in McDonald's Happy Meals, people are motivated to limit their portion size. As it turns out, the combination of a half-sized portion and a non-food gift stimulates the same part of the brain - the area responsible for reward, desire, and motivation - as the full-sized portion alone.
The study also discovered that, regardless of hunger, most people will choose a half-sized portion of food if it's paired with a toy or monetary prize rather than a full-sized portion at the same price. Even though they ate less, people who chose the incentivized option didn't consume more calories later in the day. So, if you're looking to shed some pounds, opt for the Happy Meal: you'll get to keep your skinny jeans and have a new toy!