What gets you moving? Is it a picture of the swimsuit you want to wear on vacation, or the satisfaction of achieving a tough goal? Instead of a reward, think about punishing yourself. Researchers at the University of Pennsylvania have found that punishments are more effective than rewards when it comes to encouraging physical activity.

It’s the psychological concept of loss aversion, meaning that most people prefer to avoid losses rather than acquire gains. The study, published in the journal Annals of Internal Medicine, evaluated the habits of more than 200 overweight people for 13 weeks.

Separated into four groups, the subjects were enticed to lose weight in various ways. Two of the groups had cash at stake for walking 7,000 steps a day. One group earned $1.40 every day they met the goal, while the other group lost $1.40 from a $42 “virtual account” every day they failed to meet the goal.

The third group was eligible to win either a $5 or $50 lottery each day they achieved their goal. The fourth group received nothing except feedback.

So which group was most successful? The group that was penalized financially for missing its goal. They met the walking goal 45 percent of the time, while the groups that earned a monetary reward or the lottery entry were successful 35 percent of the time. Participants in the no-reward group only succeeded 30 percent of the time.

If weight loss is your goal, start with your mind. Visualize a slimmer you, set realistic expectations for gradual weight loss and consider setting up a system for penalizing yourself. Every missed workout can be a withdrawal from a real or virtual account, and bring you one step closer to your fitness goal.