Saturday, 18 April 2009

How Many Calories Do We Need?

There are two schools of thought when it comes to counting calories for weight loss:

1. Don't waste your time and focus on the quality of your diet.

2. It's an essential tool for weight loss.
As one
doctor specializing in weight loss I worked for put it: "before you buy something it's a good idea to know how much is in your bank account, how much you make a month and how much it costs. As far as weight goes, it's currency is Calories and therefore it's a good idea to know how many Calories you burn in a daytime, how many you've had and how many you want".

I go back and forth on this one. However, if you agree with the latter school of thought, the following will help you:

How to determine how many calories you consume?

1. Measure your serving size using measuring cups and spoons.

2. Read the label: look at the serving size and the calories for that serving size.

3. Calculate and write down the calories in your serving.

For example: If you ate 4 cookies and the label on the cookie bag indicates that there are 100 calories for 2 cookies, you ate (2 x 100 calories) 200 calories.

You can use the online program
Calorie King to determine calories in foods without labels (ie. produce).

How to determine how many calories you need?

Of course, caloric needs vary widely, depending on factors like gender, age, height, weight and physical activity.
Dietitians use various equations to calculate caloric needs and in 2005, the Journal of the American Dietetics Association published a review of the various equations used (Harris-Benedict, Mifflin-St Jeor, Owen, WHO/FAO/UNU). The Mifflin -St Jeor equation was found to be the best (for both obese and non-obese individuals), predicting Resting Metabolic Rate within 10% of the measured value.

The Mifflin-St Jeor equation below estimates your Basal Metabolic Rate (BMR: the minimum number of calories your body needs to maintain your weight at complete rest). You must multiply the value obtained by an Activity Factor.

Remember that this equation is an estimate only of your caloric needs since many factors affect metabolic rate. It is meant only for healthy, non-pregnant adults.


Male: 10×weight + 6.25×height - 5×age + 5

Female: 10×weight + 6.25×height - 5×age - 161

Weight: in kilograms. If you know your weight in pounds, divide by 2.2 to obtain to get your weight in kilograms.

Height: in centimeters; if you know your height in inches, multiply by 2.54 to get your height in centimeters

here for an online BMR calculator that uses the Miffline-St Jeor equation. You must multiply your BMR with the appropriate Activity Factor to determine your daily caloric needs for weight maintenance:

Activity factor:

If you are sedentary (little or no exercise) : 1.2

If you are lightly active (light exercise/sports 1-3 days/week): 1.375

If you are moderately active (moderate exercise/sports 3-5 days/week): 1.55

If you are very active (hard exercise/sports 6-7 days a week): 1.725

If you are extra active (very hard exercise/sports and physical job or intense training, ie. twice a day): 1.9

Is weight loss a goal for you?

For a reasonable and healthy weight loss of 1lbs a week, subtract your total daily caloric needs measured above by 500 calories:

Daily caloric recommendation for weight loss: (BMR x Activity Factor) - 500

Remember that a woman should never consume less than 1200 calories a day and a man should never consume less than 1500 calories a day.


Balance, Joy and Delicias! said...

really good post, thanks for the info. Can i link it in my blog? And also I'd like to share your answer to my previous question in my blog, I think my blog friend would love to read about it.

Dietitian for Hire said...

nice post

Sybil Hebert, RD said...

Thanks Coco- of course you can link it in to your blog :)

Sweta said...

Very informative post.

Kevin in Manila said...

Here's a little more simple formula for caloric needs:

How Many Calories Should I Eat?

The numbers end up being similar to what you have mentioned.