Eating well on the Planet Earth

Your Ideal Weight

History of Weight Formulas

The first commonly used formula for finding a person's ideal body weight was devised in 1871 by a French doctor idd Broca. In 1974 a doctor idd Devine published basically the same formula only using the metric system, for the purpose of calculating the dosage of medications for patients. Unfortunately the formula wasn't even based on a real population, and isn't a good standard for healthy weight for many people. Here is the basic formula:

Devine Formula
For men: Ideal Body Weight (in kilograms) = 50 + 2.3 kg per inch over 5 feet.
For women: Ideal Body Weight (in kilograms) = 45.5 + 2.3 kg per inch over 5 feet.

This translates to 110 pounds for the first 5 feet of height in men, and 100 pounds for the first 5 feet in women. Then, you are allowed 5 pounds per inch of height after 5 feet! This is an unacceptable body weight for many people to maintain, and in fact is so close to the lean body weight (weight of just the bones and organs with no fat) in short women that it leaves room for no body fat at all! Many websites use the Devine formula in their body weight calculators, so if you think the ideal weight you are hearing is impossibly low, you may be right.

In 1984 two more formulas were published by a Doctor Robinson and a Doctor Miller.

Robinson Formula
For men: Ideal Body Weight (in kilograms) = 52 kg + 1.9 kg for each inch over 5 feet.
For women: Ideal Body Weight (in kilograms) = 49 kg + 1.7 kg for each inch over 5 feet.

This translates for men to roughly 115 pounds for the first 5 feet and another 4 pounds per inch. For women 108 pounds for the first five feet and another 4 pounds per inch.

Miller Formula
For men: Ideal Body Weight (in kilgrams) = 56.2 kg + 1.41 kg for each inch over 5 feet
For women: Ideal Body Weight (in kilograms) = 53.1 kg + 1.36 kg for each inch over 5 feet.

For men this is roughly 125 pounds for the first 5 feet and 3 pounds for every inch above that. For women it is 117 pounds for the first 5 feet and another 3 pounds for each inch.

These last two formulas present the same problems for taller men as the Devine does for shorter women, that it puts you at a weight that is impossible and unhealthy. None of these formulas takes into account age, health conditions, or muscle mass. Since everyone is unique and has their own body type and needs, it is probably not wise to try to pinpoint a single weight and say that we should all be striving for that number.

The Metropolitan Life Insurance company came out with a Height and Weight table in 1943 that gave a range of what they called "desirable" weights, or weights where you would find the lowest rate of mortality. These tables were revised in 1983. They are better because they offer a range rather than a specific target weight, and you select your range based on your frame size. However people tend to be subjective about choosing frame size, and once again the table gives an impossibly low weight range for some heights. You can take a look at the Met Life tables here.

Many doctors now use BMI, or Body Mass Index, to calculate whether a person's weight is within a healthy range. The formula for BMI is:

Metric system: weight (in kilograms) divided by [height (in meters) squared]
English system: weight (in pounds) divided by [height (in inches) squared] x 703

Note that these tables are written for adults over 20 years old, not for growing children. There is a different BMI calculation for children, and the height and weight charts are also different for the younger age groups.

The BMI doesn't account for muscle mass so that an athlete may register in the overweight group. Here is how the BMI number corresponds to weight:

Below 18.5 is underweight
18.5 to 24.9 is normal
25 to 29.9 is overweight
30 and above is obese

To summarize, there really isn't a foolproof way to determine your ideal weight. The best thing is to use a range for your height or age group such as listed in the MetLife tables, and then take into account your age, your activity level and muscle mass, and any other factors that make you uniquely you. At YOUR ideal weight you should feel healthy and comfortable with yourself and have a good level of energy. Check with your doctor or a dietitian if you are unsure what your weight should be, or if you have health problems that affect your weight and your diet.

Calculating Your Caloric Needs

The Harris-Benedict Equations were developed in the early 1900's by Francis G. Benedict, working at Nutrition Laboratory of the Carnegie Institution of Washington in Boston, Massachusetts. They were developed in order to give a benchmark for comparing the basal metabolism of people with certain diseases, but they still remain the most commonly used formula today for calculating energy needs. Here are the steps for finding the number of calories you need each day:

First: Find your basic calorie needs using the Harris-Benedict Formula.
Second: Multiply this number by an Activity Multiplier based on your activity level.
Third: Add or subtract calories from this number based on how quickly you want to gain or lose weight.

Harris-Benedict Formula for BMR

This method takes into account your height, weight, age and sex. You can use the English or metric system to figure out your BMR. I tried both ways and the result differed by only one calorie, so use whichever you are more comfortable with. Convert your measurements from English to metric, or vice versa.

For women: 655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)

Or, if you want to use metric measurements:
655 + (9.6 X wt in kg) + (1.8 X ht in cm) -(4.7 X age in years)

For men: 66 + (6.3 x weight in pounds) + (12.9 x height in inches) - (6.8 x age in years)

Or, if you want to use metric measurements:
66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)

You are going to figure out everything in parentheses FIRST. Then, do your adding and subtracting from left to right. For example with the women's calculations above you end up with 665 + total in parentheses + total in parentheses - total in parentheses.

See some examples to help with the math.

You can see from this formula how age affects your metabolism. That last number increases as you age, and you have to subtract that from the calories you are allowed to eat every day. So as you get older you must either eat less food, or increase your exercise in order to avoid a slow weight gain over the years. You can also see that men burn off WAY more calories than women. Life is so unfair.

The Activity Multiplier

Next you will calculate the extra energy you need for your activities. After finding the number of calories you need to just carry on, you will use an Activity Multiplier to take in to account the exercise you are getting, or your active lifestyle. If you are a real couch potato, the Activity Multiplier probably will not help you much. If you think the number you have so far is shockingly low, activity is your chance to bring it up to a level where you can eat a normal diet. You will multiply your BMR by a number based on your normal activity level. Here are the activity guidelines:

Examples of light activity are walking slowly, easy bicycling, light housework. Moderate activities are a brisk walk, dancing, playing ping-pong, skating, or anything that warms you up. Heavy activity would be running, bicycling fast or on hills, swimming, high intensity games like basketball or soccer. Basically, working up a sweat. Boxing, rowing and mountain climbing are extreme calorie burning activities. So what if you go for a light walk 6 days a week? Instead of using the light activity rate you could bump it up to the moderate rate. In other words, use your own judgement if you don't fit exactly in these guidelines, but be honest with yourself. You will be able to tell soon enough if your results are working to help you maintain or lose weight.

How to Use the Numbers

If you want to lose weight you must eat less calories than this amount, and if you want to gain you must eat more. Your body uses 3500 extra calories to store a pound of fat, and must burn off that much extra to lose a pound. Eating only 500 calories less each day will make you lose about a pound a week. For two pounds a week you will need to adjust your intake by 1000 calories, etc. Decide how many pounds per week you want to lose or gain, then multiply that number by 500 and add or subtract it from your Daily Calorie Needs. This is the magic number that will help you achieve your goal.

For example, lets say the 45 year old woman in the example exercises lightly about 3 times per week. She will multipy her daily caloric needs by an activity multiplier of 1.375. This means her energy needs are about 2439 calories each day. If this woman wants to lose a pound a week, she will need to subtract 500 calories, reducing her calorie intake to 1939 calories a day.

Now that you know how many calories you need, how do you keep track of how many you eat? This requires a little bit of discipline, being mindful of everything that goes into your mouth, and taking the time to write your information down. It gets easier as you remember information from day to day and learn the feeling of eating too much or too little. But that is a story for another day soon.

Examples to Help with Math

A 45 year old woman weighs 140 pounds, and is 5"5' (65 inches) tall.

655 + (4.3 x 140) + (4.7 x 65) - (4.7 x 45)
655 + 602 + 305.5 - 211.50
1774 calories per day

A 20 year old man weighs 90 kilos, and is 183 centimeters tall.

66 + (13.7 x 90) + (5 x 183) - (6.8 x 20)
66 + 1233 + 915 - 136
2078 calories per day

Convert measurements from English to metric or metric to English

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