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Friday, December 13, 2013
If you pick up any health or fitness magazine, you’ll likely see an array of calorie recommendations. Some say 1200 per day. Another may say 1500 per day. So, how much is enough? Calories come from all the different foods and beverages we consume and provide energy for our bodies. The energy in food is measured in kilocalories (Kcal), also known as Calories (C). However, it is common practice in non-scientific writing to use the term "calorie," with a lowercase c, when discussing the energy value of food. When you see the term "calorie" in relation to diet and nutrition, it refers to the kilocalorie. Both calorie and kilocalorie are units of energy. To be precise:
1 calorie = the amount of energy (heat) needed to raise 1 gram of
water 1 degree Celsius.
1 kilocalorie (Calorie) = the amount of energy (heat) needed to raise 1 kilogram of water 1 degree Celsius.
The fat in the foods we eat provides 9 calories per gram, alcohol provides 7 calories per gram and carbohydrate and protein each provide 4 calories per gram. This is why many health professionals recommend cutting back on fat to aid in weight loss. Reducing fat intake may also be beneficial in reducing risk of heart disease, diabetes and certain cancers.
The calories (or energy) we consume from food are needed for breathing, metabolizing and absorbing nutrients, maintaining body temperature and other physiologic functions, including exercise. To maintain body weight, calories you consume must equal calories you burn (through normal bodily functions or exercise). When excess calories are eaten and not burned up by the body, the extra calories are stored as fat and result in weight gain. When fewer calories are eaten than are burned, weight loss is the result.
You can estimate calorie requirements through a variety of formulas that are based on a person's:
Therefore, everyone's calorie requirements are different. In general, most individuals need a minimum of 1200 calories per day to maintain normal physiological functions. If you consume less than this, your body may feel as though it is ‘starving’ and will lower your metabolism. You will also likely not consume enough calories to meet the RDAs for most nutrients. Very low calorie diets are not recommended for weight reduction.
A common formula used to estimate calorie needs is called the Harris-Benedict Equation (named after the scientists that developed it). It is used to determine a person's basal energy expenditure (BEE, also called basal metabolic rate, or BMR). This represents the amount of energy (calories) the person uses for basic bodily processes, such as breathing and maintaining blood pressure. The BEE does not take into account a person’s physical activity.
Your TEE, or total energy expenditure, is your BEE multiplied by an activity factor. This is the amount of energy you use during a normal day, including calories for physical activity. To put this in context, your BEE are the calories you need to carry out normal bodily functions such as breathing and maintaining body temperature. Your TEE takes into account how active you are. Are you a couch potato, or a marathon runner? The TEE takes into account the extra calories your body needs to keep up with your daily activity.
Decreasing your daily activity level, or eating more calories than you need to support your daily TEE will lead to weight gain. Increasing your activity level, or eating fewer calories than your body needs, will lead to weight loss. To calculate your BEE and TEE,
Last Reviewed: Mar 31, 2006
Lisa Cicciarello Andrews, MEd, RD, LD
University of Cincinnati