Just because you buy in bulk doesn't mean you have to eat in bulk. In fact, buying in bulk can actually help you reach your goals to healthy living by making healthy foods more budget-friendly and by giving you the tools needed to control portions.
The study concluded that varying the "regular" portions affected how much the subjects actually ate. Subjects ate more food when the portion was labeled "regular" than when it was labeled "double-size" despite the fact that the two sizes were actually the same size.
Many of us don't understand what a healthy portion size is, and for good reason. A pasta portion in a restaurant is easily three cups, and many steaks are at least a pound. Getting used to normal-sized portions is not an easy task.