Low-fat or nonfat means no calories.

Fact: A low-fat or nonfat food is often lower in calories than the same size portion of the full-fat product but many processed low-fat or nonfat foods have just as many calories as the full-fat version of the same food or even more calories.
They may contain added sugar, flour, or starch thickeners to improve flavor and texture after fat is removed. These ingredients add calories.

Tip: Read the Nutrition Facts Panel on a food package to find out how many calories are in a serving. Check the serving size too it may be less than you are used to eating.