Keith Ayoob answers the question: 'What are Calories, Why Do They Matter?' February 1, 2009 -- Question: What is a calorie and why is it important to know how many calories there are in certain foods?

Basically, a calorie is a unit of energy; it measures how much energy a food provides to the body. Here are a few points to help clear up calorie confusion: How many calories are in a pound? It has ...

Calories and kcal are used interchangeably and refer to the same amount of energy, but kilojoules require conversion. Usage may differ depending on where you live. Calories are a measure of energy.

Paired with your daily calories burned, you can determine your total calorie expenditure.

Many foods are high in calories, but fat contains the most calories per gram. Some high calorie options, such as avocado, nuts, and seeds, are also dense in nutrients. There are many reasons people ...

Calories alone won't tell you if a food will make you gain weight because they don't account for nutritional value, Dr. Robert Lustig told Insider.