Britannica Sources used in this answer

How do food labels show the energy and nutrient content of foods?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A woman with curly hair and a handbag shops at a busy outdoor farmer's market in Bulgaria, surrounded by stalls filled with fresh fruits and vegetables. — nutrition Vegetables are an important part of a balanced diet.

Food labels provide essential data for evaluating the energy and nutrient content of an individual's diet. These labels are standardized to ensure they are honest and informative, a requirement overseen in the United States by the Food and Drug Administration under the Fair Packaging and Labeling Act.12

Energy content on labels is typically expressed in kilocalories, commonly referred to as "calories." This value is derived from the energy-yielding components of the food: carbohydrate, protein, and fat. The physiological energy values used for these calculations are approximately:1

Carbohydrate: 4 kilocalories per gram1
Protein: 4 kilocalories per gram1
Fat: 9 kilocalories per gram1

By knowing the gram amounts of these substances, the total energy of a food can be estimated. Labels also provide information on other constituents, such as vitamins and minerals, which do not provide energy themselves but are vital for the body's metabolic processes.1