Saturday, May 29, 2010

What is BMI: The Truth Revealed

With all the talk about it these days, you might be wondering, “What is BMI?” There's no magic to it, no secret formula, even though sometimes the way it's talked about it sounds like some sort of mantra for weight loss and health. BMI isn't a meditation or an exercise or diet plan, it's simply the measure of your body mass. It compares your weight and height, and boils that ratio down to a number. Depending where your number is on the scale, it tells you if you're underweight for your height, overweight, or obese.

So what is BMI, in general? BMI, or body mass index, is a tool of body mass measurement that was created in the early 1800s by Adolphe Quetelet. This is why sometimes you might see BMI referred to as the Quetelet index. Adolphe Quetelet was mathematician, statistician, and an astronomer, among other things. He developed the BMI while working on social physics. The BMI is still used today with very few variations on his original invention.

What is BMI, specifically? BMI doesn't measure body fat, but instead compares a person's weight and height to estimate a healthy body weight for that person's height. It's widely used to determine if someone is technically overweight or obese. Though it's the not the final tool in diagnosing obesity or overweight, because it's not without its flaws for certain body types, it's still in use in the medical community.

The formula for BMI is simple: Take your height in meters squared (your height times itself) and then divide your weight in kilograms by that number. For example, if I'm 5 feet tall, that's about 1.5 meters. 1.5 squared (1.5 times 1.5) equals 2.5. If I weigh 120 pounds, that's about 54.5 kilograms. So I need to divide 54.5 by 2.5 which gives me a result of 21.8 as my BMI. So what does that number mean? A BMI of 18.5 or below indicates that an individual is underweight. The normal weight range is from 18.5 to 24.9. Overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity. Someone five feet tall weighing 120 pounds falls into the normal weight range.

Where BMI fails is with extremely muscular people. It doesn't distinguish between muscle and fat, instead using total weight as the measure. So according to the BMI, bodybuilders are likely to measure as obese which is inaccurate. Most athletes like wrestlers, footballs players and any athletes with a large amount of lean muscle are going to measure as overweight or obese. But for most people, BMI is a fairly accurate measure of their level of underweight or overweight.

Now that you know the formula, you know that BMI is as simple as a single math problem, and a single number. Next time you're faced with the question, “What is BMI?” you'll know there's no magic to it, it's simply a measure of a person's body weight compared to his or her height.

Friday, May 28, 2010

Tips About the BMI Index

The BMI Index is a tool that was invented in the early 1800s. While there aren't many health and fitness tools that were created in the eartly 1800s that we're still using today just as they were, the BMI index is relatively unchanged in almost 200 years. It's still a popular tool used to figure out if a person's weight is healthy. The BMI simply compares your weight to your height and decides if you're underweight, a normal weight, overweight or obese. Most of us can look in the mirror or notice whether or not we're having to squeeze into our pants, and determine this without the use of numbers and calculations. But that doesn't stop the BMI from being widely used by doctors, and worse, insurance companies.

Insurance companies frequently use a person's BMI to determine if the person is a risk to insure. Health insurance costs can be higher for those who have a BMI in the overweight or obese range, and life insurance can be higher or it can be refused completely. While it's within these companies' rights to refuse to insure anyone, the use of the BMI index to make that determination represents flawed thinking, unless other factors are considered, too.

The BMI Index determines a person's BMI by dividing their weight by their height squared (their height times itself). When kilograms and meters are converted into pounds and feet or inches, the formula changes very slightly, but the resulting BMI number is very close the number obtained by using kilograms and meters. For most people, the BMI Index is a decent measure of their weight in proportion to their height. But for some, it comes up with a label that's far off.

Consider a championship bodybuilder. He's one of the best in the world in the lightweight division, at 5' 3” and 154 pounds. The man is solid muscle, and he's in amazing physical shape. The BMI Index says he's overweight and needs to lose weight. When you take his height times itself and divide that into his weight, he comes up with a BMI of almost 27. The cut-off for normal weight is 24.9. Clearly, he's not overweight, with barely an ounce of body fat anywhere. But an insurance company won't care about that, they could refuse him insurance based on his 'high-risk' BMI.

Once you've used the formula to figure your number on the BMI Index, you can see where you rank as far as healthy weight. A person is underweight with BMI of 18.5 or below. The normal weight range is from 18.5 to 24.9. From 25 to 29.9 indicates that you're overweight. And anyone with a BMI of 30 or over is considered obese. Try plugging in some professional athletes' heights and weights, and see how many are classified obese with the BMI Index.

This makes it clear that while it's a valuable tool, common sense, appearance and body fat must be considered along with the BMI Index to determine a person's ideal weight.

Thursday, May 27, 2010

The Truth About Mothers and their Daughters' Resemblance on BMI Charts

Is it true that mothers and their daughters' resemblance on BMI is a sure thing? It's easy to assume that a daughter might take after her mother's eating habits and have a similar BMI as her mother, for many reasons. But they might not be the reasons you'd think. But first, let's make it clear what BMI is.

BMI or body mass index is nothing more than the measure of a person's weight in relation to her height. A person's weight in kilograms is divided by a person's height in meters, squared (which is simply a person's height times itself—if I'm 1.5 meters tall, I would take 1.5 times 1.5). The resulting number is her BMI. A normal BMI is anything from 18.5 to 24.5, and 25 to 29.9 is considered overweight, with anything above that considered obese. A BMI below 18.5 is considered underweight. BMI is a good general measurement for most people, although very muscular people usually measure as overweight or obese because BMI doesn't distinguish between muscle weight and fat weight.

So, back to mothers and their daughters' resemblance on BMI, does it guarantee that a daughter will be overweight if her mother has a high BMI? Will a normal weight mother raise a normal weight daughter? Will the daughter be underweight if the mother is too skinny? While nothing is certain 100% of the time, there are some factors that push those answers more toward a yes than a no.

Genetics do play a part in a person's tendency toward staying thin or gaining weight. Hereditary factors like body type are impossible to change. Tendency toward a slow metabolism can be boosted by exercise, good nutrition and a healthy lifestyle, but genetics will help determine how easy or difficult keeping a high metabolism may be for a daughter.

The environment is a huge factor. When a mother is overweight, for example, and she generally cooks for the family, the family eat what she eats to a large degree. So it's easy to see why mothers and their daughters' resemblance on BMI is often very similar. Living with a person, especially someone with the influence a mother has on a daughter, also tends to shape a person's attitudes. So if the mother is very active, eats healthy and stays physically fit, it's more likely than a child, especially a daughter, will do the same. Conversely, a mother who is overweight, rarely gets exercise and doesn't seem overly concerned with weight loss or health is likely to bring up her daughter with the same outlook. In both cases, it's no surprise that their BMIs might be similar.

So not only do the attitudes about food and fitness filter down from mothers to daughters, the type of food eaten, and even the amount of food eaten, can filter down, too. Mothers and their daughters' resemblance on BMI charts is no coincidence, and only shows the need for families to be aware of their health and fitness even when children are small.

Wednesday, May 26, 2010

The Truth About BMI, Body Fat and Health

Though one of the most popular tools used today to determine whether someone is at a healthy weight or not is the BMI, body fat and lean muscle tissue don't figure into the equation. This has led many experts to discount BMI as an archaic measurement that isn't accurate for many people. What is BMI, and why is it a good measure for some, maybe, and completely wrong for others?

BMI, or body mass index, was created in the early 1800s by Adolphe Quetelet. Because of that, it's sometimes called the Quetelet index. It's nothing more than a way of comparing a person's weight to his or her height, and determining if his or her weight falls into a healthy and normal range. The BMI is still used today pretty much as it was when Quetelet invented it.

The formula for figuring BMI (body fat, bone and frame size, muscle and body type aren't included in that) is this: Take your height in meters squared (your height times itself) and divide your weight in kilograms by that number. For example, if I'm 5 feet tall, that's about 1.5 meters. To square that number, take 1.5 times 1.5. The result of that is 2.5. So if I weigh 120 pounds, that's about 54.5 kilograms. Divide 54.5 by 2.5 and I get 21.8 as my BMI. The normal weight range is from 18.5 to 24.9, so 21.8 is classified as a normal weight. Underweight is considered 18.5 and below, while overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity.

BMI, body fat and general health can all be used as signs of how fit a person is. But where general health is pretty self-explanatory and the percentage of body fat clearly shows whether a person gets enough exercise or not, BMI is a bit trickier.

People with a lot of muscle don't show accurate BMI readings. Because muscle weighs so much heaver than fat but takes up less space, a relatively small statured person can carry a lot of muscle weight without looking huge. BMI doesn't take that into account. Football players, professional wrestlers, bodybuilders, and virtually any athlete who has a lot of muscle is going to measure as overweight and even obese according to the BMI. So it's not accurate for them. Is it accurate for everyone else?

The answer to that is yes, and no. It depends on you. The BMI typically doesn't show an accurate result for children. And extremely tall or large-framed people will show overweight or obese classifications more easily because of the extra weight from their bones and muscles. So for very short, tall or muscular people, the BMI appears to not be a good tool.

There's also no distinguishing between men and women in the BMI. Body fat is more natural for women who are supposed to have more than men, so some sort of distinction in the measurement of the sexes would help the BMI's accuracy.

Tuesday, May 25, 2010

Learn the Secret of BMI Calculations

BMI calculations might seem like some esoteric and complicated process that you have no hope of figuring out. That's not true. BMI isn't magic or some scientific secret withheld by those in the know. If you've ever used a BMI calculator online, then you know that you put in your height and weight, and it cranks out special number. There's always a chart handy, or the website interprets it for you, and tells you whether you're underweight, normal weight, overweight or obese, all based on this single number. The website did the calculations for you, but you might be wondering just how it arrived at that number. BMI calculations are fairly simple once you understand the basic formula. But first, let's look at what BMI is and what BMI calculations are used for in the first place.

BMI is the measure of body mass. By comparing your weight and height, specifically dividing your weight by your height, squared, the BMI calculations give us a single number. Depending on where that number falls on a special scale, it tells you if you're underweight for your height, in the normal range, overweight, or obese.

BMI doesn't measure body fat, however, so often the number is wrong when it comes to athletes or very muscular people. Muscle weighs more than fat, so for them, BMI isn't an accurate measure at all. For most people, though, it's a very good estimate of weight in relation to height. So what BMI calculations allow us to arrive at that magic BMI number?

BMI calculations may seem complicated, but they're really not. At its most basic, the formula is kg/m2. Or your weight in kilograms divided by your height in meters, squared (your height in meters times itself). A person who's five-and-a-half-feet tall stands about 1.7 meters. Square that number (1.7 times 1.7) and you come up with 2.89. A person who weighs 150 pounds weights about 68 kilograms. So the BMI calculations to determine this person's BMI would be 68 divided by 2.89. The result of that is about 23.5.

A BMI of 18.5 or below indicates that an individual is underweight. The normal weight range is from 18.5 to 24.9. Overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity. So a person with a BMI of 23.5 is within his or her normal weight range, according to the BMI calculations.

If you don't want to convert feet and pounds to meters and kilograms, then you can use one of the other BMI calculations to figure your number. This person's new formula would be weight in pounds, 150, times 4.88, or 732, divided by height in feet squared (5.5 times 5.5) which is 30.25. Then divide weight by height squared (732 divided by 30.25) and the result is 24.1, very similar to the metric formula's result. BMI calculations can also be done by taking weight in pounds times 703, and dividing by height in inches, squared.

Monday, May 24, 2010

Calculating BMI, Made Easy

Before we start calculating BMI, let's discuss what BMI is, and what it isn't. BMI, or the body mass index, is a tool that's used to determine whether or not a person is at a normal weight for his or her height. It was invented between 1830 and 1850 by mathematician and scientist Adolphe Quetelet. Though it's been almost 200 years since he created the BMI, it's used today almost exactly as he outlined.

While BMI isn't the final word in whether or not someone is at a normal weight, it's one of the first tools often used to determine if someone's overweight. Because the BMI doesn't distinguish between weight from fat and weight from muscle (other tools must be used to determine the actual amount of fat) it doesn't work well for very muscular people like athletes. But for most of us, BMI is a pretty accurate measure of whether we're underweight, a normal weight, overweight or obese.

Calculating BMI isn't difficult once you understand the formula. The basic formula is weight divided by height squared, or kg/m2. You simply take your height in meters and square it which means you take the number of meters times itself. Then divide that number into your weight in kilograms. So a person who's five-and-a-half-feet tall stands about 1.7 meters. To get 1.7 meters squared, you simply multiply 1.7 times 1.7, which equals 2.89. Now, convert weight to kilograms.

So if someone weigh 200 pounds, that's about 91 kilograms. To determine the BMI of someone about five-and-a-half-feet tall who weights 200 pounds, or who stands 1.7 meters tall who weights 91 kilograms, we divide the weight by the height squared, or 91 divided by 2.89. That gives us the result of about 31. This individual is classified as obese. How do I know that?

A BMI of 18.5 or below indicates an underweight person. The normal weight range is from 18.5 to 24.9. Overweight people will have a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity. So a person with a BMI of 31 is in the obese range, but not by much. By calculating BMI again with different weights, you can see that the person would only need to lose 5 kilograms, or about 11 pounds, to no longer be obese, but merely overweight. And a loss of 19 kilograms, or about 42 pounds, will put this person within a normal weight range. Calculating BMI to determine how much weight one should lose can be a big help for someone who's not sure.

Calculating BMI can be made even more simple if you're not sure how to convert to kilograms or meters. Simply take your weight in pounds times 4.88. Then divide that number by your height in feet, squared. So a 200 pound person who is 6 feet tall: 976 divided by 36 = 27.1. After calculating BMI, it's clear this person is within a normal and healthy weight range.

Sunday, May 23, 2010

Body Mass Index (BMI): Are You at a Healthy Weight?

The body mass index, or BMI, helps clarify an important distinction between being overweight or being obese. If you weigh too much, you're obviously overweight. But if you have a very high proportion of body fat, you're obese. Based on your body mass index, your doctor or other health professional will classify your weight as healthy, overweight, or obese.

According to the National Heart, Lung and Blood Institute (NHLBI), the BMI "describes body weight relative to height and is correlated with total body fat content in most adults". In almost all cases, this means that the BMI will accurately reflect your weight and proportion of body fat as a function of your height and weight when categorizing you as healthy, overweight or obese.

Calculating your approximate body mass index is relatively straightforward, although you'll probably need a calculator just to save time. To get your BMI, multiply your weight in pounds by 703. Next, divide that result by your height in inches. Then divide that result by your height in inches one more time.

As an example, let's say you weigh 180 pounds and are 5 feet 10 inches tall.

Multiply 180 by 703 to get 126,540. Next, divide this by 70 (70 inches is the same as 5' 10") to get 1807.7. Now, divide 1807.7 by 70 one more time. The result -- 25.8-- is your approximate BMI or body mass index. If you don't have a calculator handy, you can get the same result using the free interactive BMI calculator.

If the above example sounds you, you might be surprised to learn that you're ever so slightly heavier than your doctor might like. A BMI from 18.5 up to 25 is considered healthy, from 25 up to 30 is classified as overweight, and 30 or higher is obese.

Generally, says the NHLBI, the higher a person's BMI, the greater the risk for health problems. In addition to causing your BMI to skyrocket, excess body fat is a well recognized health risk. Men and women with waist lines in excess of 40 and 35 inches, respectively, are much more at risk for health problems like Type 2 diabetes, high blood pressure and high cholesterol.

Like every rule of thumb, this one also has it exception. Body builders, for example, often have a body mass index above 25 and sometimes even above 30. In this case, however, the higher BMI reflects the fact that body builders have more muscle mass without having more fat.

Finally, there's still only one sure way to lower your BMI if you're overweight or obese: Eat less and exercise more. Your body will burn more calories than you eat and your body mass index will go down over time.