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How To Lose Weight Rationally

Is there just one real formula for weight loss? Not everyone wants to believe it, but your body weight is really the result of a mathematical formula. When you eat the same number of calories per day as your body burns, then your weight stays the same. Eat more than you burn and you gain weight. Eat less than you burn and you lose weight.

That's really all you need to know about losing weight. Or is it? What about all the diet plans that ask you to count points or grams of carbohydrate or grams of fat? What about the plans that say calories don't count? What about the plans that say they can "fool" your metabolism into violating the formula?

Well, the plans that use points or grams are really just giving you an alternate way of counting calories. There may be certain metabolic advantages to low carb plans, but in truth the jury is still out. As for the plans that try to trick your body into giving up weight some other way, all I can say is "You can't fool Mother Nature," at least not for very long.

Your body's food intake and energy expenditure works very much like a budget. When you earn more than you spend, you accumulate savings. When you spend more than you earn, you accumulate debt. In your financial budget savings are what you want, but in your calorie budget you're looking for a calorie debt or deficit if you want to lose weight. Just remember that weight loss equals calorie deficit, and you won't go wrong.

I'm about to go all mathematical on you, but please stay with me at least for the rest of this paragraph, because there is hope. If you don't want to bother with some arithmetic and a couple of formulas, go ahead and skip to the bottom of this article where I'll tell you about an automated alternative. But if you're interested in the details, keep going.

Here's the formula in mathematical terms:

(Calories Consumed) - (Calories Burned) = (Calorie Deficit if negative) or (Calorie Excess if positive)

Here are a couple of examples to make this clear.

Say you eat 2400 calories per day and you burn 2200. You have:

2400 - 2200 = 200

Since 200 is a positive number, you have an excess of 200 calories that day. If you keep it up, you'll gain weight.

Or say you eat the same 2400 calories but you burn 2700. Then you have:

2400 - 2700 = -300

This time the result is a negative number, -300, which means you have a deficit of 300 calories that day. If you keep it up you'll lose weight.

This raises some obvious questions, doesn't it? One, how much weight will I gain or lose? And two, how do I know how many calories I'm burning each day?

Very good questions. In the rest of this article I'll answer them and give some of the implications.

First, what's the relationship between the calories and the poundage? Approximately this: 3500 calories equals one pound. That's the rule of thumb. So if you could have a consistent calorie deficit of 500 calories per day, on the average you would lose weight at the rate of one pound per week (since 500 x 7 days = 3500 calories).

Notice that I said "on the average." That's because your weight does fluctuate from hour to hour and from day to day. It fluctuates generally within a three-to-five pound range due primarily to changes in water retention and to how full your stomach, bladder and bowel are at any given moment. So don't judge your results by a few isolated weigh-ins. Instead watch the trend over a period of weeks.

If instead of one pound a week you want to lose two pounds a week, you need to create a deficit of 1000 calories per day (since 1000 x 7 days = 7000 calories). That's a lot for most people. Unless you're extremely active (an athlete or a physical laborer) it will be very difficult to create a larger deficit and lose weight any faster.

Okay, now for the second question. How many calories are you burning? This is more difficult because the only way to get a really precise answer is to live inside a sealed chamber in a laboratory. But we do have some formulas that give an approximate answer based on averages. These are the best estimates available, but your mileage may vary. You really have to experiment on your own body to see.

These formulas have two parts. First you calculate your BMR, or basal metabolic rate. This is the number of calories you would burn if you did nothing but lie in bed all day. Then you multiply by a factor that represents how active you are (compared to lying in bed all day). That gives your approximate MR, or metabolic rate.

Here we go. The formulas for basal metabolic rate are:

For men, BMR = 66.4730 + (6.2507 x W) + (12.7084 x H) - (6.7550 x A)

For women, BMR = 655.0955 + (4.347 x W) + (4.698 x H) - (4.6756 x A)

Where BMR = basal metabolic rate (energy production) per 24 hours at complete rest in calories, W = weight in pounds, H = height in inches, and A = age in years.

That gives your basal metabolic rate (BMR). Then you apply one of these factors to account for your activity level and compute your metabolic rate (MR), the calories burned per day:

1. If you get little or no exercise: MR = BMR x 1.2

2. If you get light exercise 1-3 days/week: MR = BMR x 1.375

3. If you get moderate exercise 3-5 days/week: MR = BMR x 1.55

4. If you get hard exercise 6-7 days a week: MR = BMR x 1.725

5. If you get very hard exercise or have a very physical job: MR = BMR x 1.9

Let's do a couple of examples to be sure there's no confusion. Suppose you're a woman, age 34, 5 foot 4 inches tall, 128 pounds, getting moderate exercise. Here's the calculation. (Remember that 5 foot 4 equals 64 inches.)

BMR = 655.0955 + (4.347 x 128) + (4.698 x 64) - (4.6756 x 34)

BMR = 655.0955 + 556.416 + 300.672 - 158.9704

BMR = 1353.2131

MR = BMR x 1.55

MR = 2097 calories per day

Now we'll do one for a man, age 55, 5 foot 10 inches, 180 pounds, getting light exercise:

BMR = 66.4730 + (6.2507 x 180) + (12.7084 x 70) - (6.7550 x 55)

BMR = 66.4730 + 1125.126 + 889.588 - 371.525

BMR = 1709.937

MR = BMR x 1.375

MR = 2351 calories per day

Now, putting it all together, for our hypothetical man who's burning 2351 calories per day at his present weight and activity level, if he wants to lose weight at the rate of 1-1/2 pounds per week, he would need to create a calorie deficit of 5250 per week (that's 3500 x 1.5) or 750 per day. So he would need to consume 1601 calories per day (2351 - 750) consistently in order to lose at that rate.

Notice one interesting fact. If this man wants to eat more than 1601 calories a day and still lose weight at the rate of 1-1/2 pounds per week, he can raise his activity level to moderate from light. That changes his MR from 2351 to 2650. So he can eat about 300 more calories per day at this higher level of activity, and he'll still lose weight at the same rate.

Now, I promised you an automated way to do all these calculations. I know of only one online weight loss calculator that has all this built in. Read the resource box, below, to see where to find it.