How to Calculate Calories for Weight Loss

This was my project for this morning: figuring out how many calories I can eat and still lose weight. The fact is, no matter how healthy and low-fat I eat, if my calories in, exceed my calories out (by physical activity and just being alive), I am still going to gain weight. Duh. So, I went online searching for tools to help me determine how many calories I should cut to lose weight, without lowering my metabolism.

I already know that I don't have to get extreme with calorie cutting, in fact, it is counter-productive to do so. Cutting too many calories will cause my metabolism to slow way down, and I will lose muscle mass instead of fat. Besides, it is too hard to keep up over time. So, the easiest way to cut calories without "feeling" it, is to cut back a little at a time. Now, there are two ways to do this:

The first method I thought up was to determine how many calories I need to maintain my current weight, and how many I would need to maintain a weight of 5 lbs. less, then eat that amount until I lose 5 lbs. I can just repeat until I reach my goal!

Looking online, I found I can also use a formula to determine optimum calories for weight loss at each level of weight, based on my BMR and body fat %. I found some great tools at the following sites to do just that!

At http://www.freedomfly.net/Articles/Nutrition/nutrition14.htm Tom Venuto explains the difference between three current methods of figuring caloric needs, as well as three formulas to do it yourself.

There is the quickie formula that simply says "Fat loss = 12 - 13 calories per lb. of body weight; Maintenance = 15 - 16 calories per lb. of body weight; and Weight gain: = 18 - 19 calories per lb. of body weight." Now, this method does not take into account your activity or exercise levels, or lean body mass, so it will not be very accurate for those extremely overweight. I did the calculations and compared my results to the other methods listed below. The numbers were in line with the calories needed to lose weight along with moderate exercise for both the following formulas, so, it seems if you are planning to at least walk 30 minutes a day 3 days a week, then you can use this method to plan your caloric intake with reasonable accuracy.

There are two methods based on your BMR (Basal Metabolic Rate)that are considered more accurate than the one above: The Harris Benedict formula and the Katch-McArdle formula.

The Harris Benedict formula uses height, weight, age, and sex to determine BMR. It does not take lean body mass into consideration, though, so it will not be as accurate for those who are extremely muscular or overly fat. The formulas use kg. and cm. for weight and height so I have included the conversion information for those using lbs. and inches. The formulas are:

2.54 cm. = 1 inch
1 kilogram = 2.2 lbs.

Harris-Benedict formula:

Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)
Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X age in years)

You then multiply the BMR number of calories you get in the formula, by a number based on your level of exercise:

Sedentary = BMR X 1.2 (no or little exercise)
Lightly active = BMR X 1.375 (light exercise 1-3 days per week)
Moderately active = BMR X 1.55 (moderate exercise 3-5 days per week)
Very active = BMR X 1.725 (hard exercise 6-7 days per week)
Extremely active = BMR X 1.9 (hard daily exercise or physical job, or twice-daily training for marathons, contests, etc.)

The result is the number of calories you need each day to maintain your current weight. Eat 15-20% fewer calories to lose weight!

The other formula is the Katch-McArdle formula, which is considered the most accurate method as it takes your lean body mass into account. Even if you have not had a body composition test, you can still use this formula by finding out your body fat %. Go to http://www.healthyforms.com/helpful-tools/body-fat-percentage.php to use a free calculator to determine your body fat % quickly and easily.

BMR (men and women) = 370 + (21.6 X lean mass in kg), then multiply by the number above based on activity levels, as before. This is the amount of calories needed to maintain your current weight, so anything less will enable you to lose weight!

For example, today I weighed 126 lbs. I am 44 years old, 63 inches tall and my body fat % is 29. Using the quick method above, the calories I should be able to eat in order to maintain that weight are between 1890 and 2016 calories a day. This method predicts I should eat between 1512 to 1638 calories a day for weight loss.

Alternatively, I can use the calories needed to weigh 120 lbs. as my initial calorie goal, which is 1800-1920 calories a day. Now, if I do nothing more than sit on the couch and breathe all day, it will take me about a month to lose a lb. of weight (3500 calories), but any way you slice it, eating only the calories needed to maintain 120 lbs. weight will inevitably result in my weighing 120 lbs.

To make the calculations easier, I used the Body Fat Percentage Calculator and the Calorie Calculator downloaded from the above sites and got the following results using the Katch-McArdle and the Harris-Benedict formulas:

Katch-McArdle Formula Men and Women (considered most accurate method)
Activity Levels Maintain Build Mass Lose Weight
Sedentary 1498 1723 - 1798 1198 - 1273
Lightly Active 1716 1974 - 2060 1373 - 1459
Moderately Active 1935 2225 - 2322 1548 - 1645
Very Active 2153 2476 - 2584 1723 - 1830
Extra Active 2372 2728 - 2846 1897 - 2016
*Katch-McArdle Formula requires input of Weight and Body Fat Percentage only.

OR:

Harris-Benedict Formula Women
Activity Levels Maintain Build Mass Lose Weight
Sedentary 1538 1768 - 1845 1230 - 1307
Lightly Active 1762 2026 - 2114 1409 - 1498
Moderately Active 1986 2284 - 2383 1589 - 1688
Very Active 2210 2542 - 2652 1768 - 1879
Extra Active 2435 2800 - 2921 1948 - 2069


So, final tally for losing weight (with no exercise):
My 5 lb.s at a time method: 1800-1920 calories a day.
Quick formula: 1890-2016 calories a day.
H-M formula: 1230-1307 calories a day.
K-M formula: 1198-1273 calories a day.

Obviously, there is quite a bit of disparity between the first two methods and the last two. Since I do use my treadmill six days a week, walk my dogs daily, and garden now that the weather is nice, I am going to use the K-M formula with moderate exercise, which allows me about 1600 calories a day. I am going to break that up into 5 meals, ending at 8 p.m. nightly, of 320 calories each. Yes, I am planning a glass of wine or beer, and/or dessert into that last meal! I will let you know how it goes. Right now I am going to eat lunch - the whole 320 calories of it!

Some resources for you to help count calories:
The Complete Book of Food Counts, 8th Edition

Rocketech Count Down to Slim Calorie, Carb and Fat Counting System

The Everything Calorie Mini Book: Quick and Easy Calorie Counts for All the Foods You Love to Eat (Everything (Mini))

Weighmax Nutrition Scale. Counts Calories, Salt, Protein, Fat, Carbohydrate, Cholesterol & Fiber - Kitchen & Diet Scales