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What are calories? 

Calories are a measurement of energy.A calorie was originally defined as the amount of heat required to raise the temperature of 1 gram of water 1° Celsius at a pressure of 1 standard atmosphere.One calorie is equivalent to 4.18 kJ.

How many calories should I eat in a day?

The amount of calories an individual needs in a day varies greatly from person to person. Factors such as age, gender, body surface area, and activity level are all considered when estimating calorie needs. In general, women need roughly 2,000 calories per day and men need roughly 2,500 calories per day. As activity level increases, calorie needs will also increase. 

What is a calorie deficit?

A calorie deficit occurs when calorie intake is below the required calorie needs. A caloric deficit can be created by either eating less calories than needed to maintain weight, or by increasing physical activity to expend more calories. Either way, a calorie deficit will occur which results in weight loss overtime. 

How many calories should I eat to lose weight?

For healthy, sustainable weight loss, it is recommended to lose about 1 pound per week. One pound of body weight equals about 3,500 calories. Therefore, creating a calorie deficit of about 500 calories per day equates to 1 pound of weight loss per week. First, assess how many calories you are currently consuming per day. Then consider reducing caloric intake by up to 500 calories per day, or considering increasing your physical activity to burn up to 500 more calories per day. 

How many calories do I burn in a day?

The amount of calories you burn in a day depends on several factors such as gender and physical activity level to name a few. Most adults burn at least 1,200 calories a day just keeping the body alive. Outside of life sustaining activities, calories are also burned when being physically active. For example, individuals burn an average of 100 calories for every mile walked. As intensity of the physical activity increases, so do the amount of calories that are burned to perform the physical activity.To get a better idea of how many calories you burn in a day, you can experiment with different fitness tracking apps.

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Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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