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Do You Know How Many Calories To Eat Today? Most Americans Don't


According to a study published this week by the International Food Information Council Foundation, only one out of every eight adult Americans knows how many calories he or she should consume in a day. Calculating calorie needs is important throughout the lifespan, to ensure children have enough for growth and adults have enough for weight maintenance.

In a national online survey of just over 1,000 people over the age of 18, 63% cannot accurately estimate how many calories they need in a day and 25% won’t even try to guess. The study was conducted by Cogent Research of Cambridge, MA.

“There is confusion on all sides of the calorie equation,” says Wendy Reinhardt Kapsak, director of the IFICF. Although food labels often reference 2,000 calories a day for the “average American”, the information is just an estimate – each individual’s needs is different and based on factors such as age, sex, health status, and physical activity levels.

In fact, calorimetry – the measurement of energy expenditure (and therefore calorie needs) – can only actually be accomplished through laboratory testing. However, there are calculations that can help you find an estimate as a starting point for your own calorie needs.

In a clinical setting, dietitians often use a calculation called the “Harris-Benedict” equation which calculates calorie needs at rest based on age, height, and weight. The online site (bmi-calculator.net) will calculate it for you, or you can use the following equations:

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Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )

Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in years )

Once you understand your basal metabolic rate (another name for calorie needs at rest), you use an activity factor to determine your daily calorie needs:

1. If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
2. If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
3. If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
4. If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
5. If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

According to the survey, losing weight is the number-one reason why Americans calculate their calorie needs and change their diets. To best determine a calorie level for weight loss, take the above resulting calculation and subtract 500 calories. For example, if your daily calorie needs including activity factor equals 2000 calories, in order to lose one pound per week, subtract 500 and aim for 1500 calories per day.

The Harris-Benedict equation provides a good starting point for daily calorie needs. Once you adjust your intake to best meet your needs, you can monitor your progress to see if you need to adjust up or down. For example, if you are not losing weight at 1500 calories per day, subtract another 100 calories or increase your activity to burn another 100 calories. However, health experts recommend to never go under 1200 calories, as you will not meet your nutrient needs for basic good health at a lower level.