Understanding Nutrition Labels and Information Here is a guide to understanding what those nutritional claims mean: Low Calorie: Less than 40 calories per serving. Calorie Free: Less than 5 calories per serving. Fat-Free: Less than 0.5 grams of fat per serving. Sugar-Free: Less than 0.5 grams of sugar per serving. High Fiber: 5 grams or more of fiber per serving.