But while some fast-food items are healthy, it's very easy to go wrong with fast food and have a few meals undermine your resolutions.
We looked at nutritional data from restaurant chains to find the worst of the worst. Over time, some nutritional data may change slightly - but these items are still high in calories.
Find out which items have the most calories, fat, saturated fat, sodium, and cholesterol.
You'll want to steer clear of them if you're watching your waistline.
Here are the offenders, in order of least to most calories.