Obesity Discussion Forums

[MikeB]

Body Mass Index (BMI) FAQ

What is the Body Mass Index?
The Body Mass Index or BMI is a method of classifying whether an individual is overweight, underweight, obese or normal weight based only on their height and weight and is not gender specific. To calculate your BMI see the online BMI calculator. What are the classifications of the Body Mass Index?
A BMI of less than 18.5 is underweight, normal weight is between 18.5 and 25, overweight is between 25 and 30 and obese is greater than 30.
What are the BMI limitations?
The BMI does not make a distinction between fat and muscle. We have compiled a list of athletes who won Gold medals at the Athens 2004 Olympics and would be considered overweight using the BMI scale. See our BMI for athletes section, which shows that all members in the Gold medal winning GB rowing coxless four would be considered overweight using this scale. This highlights a person with a lot of muscle (such as an athlete) may have a BMI in the unhealthy range, but still be healthy and have little risk of developing diabetes or having a heart attack. BMI also may not accurately reflect body fatness in people who are under 5 feet and in older people, who tend to lose muscle mass as they age.
Can the BMI predict my ideal weight?
Yes, see our online ideal weight calculator which also calculates your BMI and estimates the time taken to achieve your ideal weight.
How is the Body Mass Index Calculated?
BMI is found by dividing a person's weight in kilograms by height in meters squared. The mathematical formula is:


BMI = weight (kg) / height squared (m²)
To determine BMI using pounds and inches, multiply your weight in pounds by 704.5,* then divide the result by your height in inches, and divide that result by your height in inches a second time. Alternatively use the online BMI calculator. Who decided the BMI ranges and how?
In 1995, the World Health Organization recommended a classification for three "grades" overweight using BMI cutoff points of 25, 30, and 40. (see Physical status: The use and interpretation of anthropometry. Report of a WHO Expert Committee. World Health Organization: Geneva, 1995 (WHO Technical Report Series; 854)).
A similar definition was released in a report in June 1998 (see Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. National Institutes of Health, National Heart, Lung, and Blood Institute. June 1998). This report was from an expert panel convened by the National Heart, Lung, and Blood Institute (NHLBI) in cooperation with the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), both part of the National Institutes of Health (NIH).
The panel identified overweight as a BMI > 25 to less than (<)30, and obesity as a BMI > 30. These definitions, widely used by the Federal government and increasingly by the broader medical and scientific communities, are based on evidence that health risks increase more steeply in individuals with a BMI > 25.
What is the relationship between body fat and the Body Mass Index?
BMI does not directly measure body fat percentage. Deurenberg et al. produced a formula to predict body fat from BMI which can be accessed from our body fat and Body Mass Index calculator An alternative to the Deurenberg calculator is the Gallagher body fat calculator. We also have alternative body fat calculators based on body part dimensions and skinfold measurments from calipers.
How accurate are the BMI classifications?
BMI cutoff points are a guide for overweight and obesity and are useful for comparative purposes across populations and over time; however, the health risks associated with overweight and obesity are on a continuum and do not necessarily correspond to rigid cutoff points. For example, an overweight individual with a BMI of 29 does not acquire additional health consequences associated with obesity simply by crossing the BMI threshold > 30. However, health risks generally increase with increasing BMI.
Is the distribution of weight important?
Excess weight, as measured by BMI, is not the only risk to your health. So is the location of fat on your body. If you carry fat mainly around your waist, you are more likely to develop health problems than if you carry fat mainly in your hips and thighs. This is true even if your BMI falls within the normal range. See our waist to hip ratio calculator. Women with a waist measurement of more than 35 inches or men with a waist measurement of more than 40 inches may have a higher disease risk than people with smaller waist measurements because of where their fat lies.
What are the dangers of extra weight?
Extra weight can put you at higher risk for these health problems - type 2 diabetes (high blood sugar), high blood pressure, heart disease and stroke, some types of cancer, sleep apnea (when breathing stops for short periods during sleep), osteoarthritis (wearing away of the joints), gallbladder disease, liver disease and irregular menstrual periods.
Who invented the Body Mass?
The modern Body Mass Index or BMI calculation is based on the work of the Belgian mathematician, Lambert Adolphe Jacques Quételet who published a study of the average man in 1835 entitled "A Treatise on Man and the Development of His Faculties" ISBN 0820110612. This also explains why the BMI is sometimes referred to as the Quetelet index.
What are the alternatives to the Body Mass Index?
An alternative classification scheme uses the waist to hip ratio (see our online waist to hip ratio calculator) to measure vascular health risk. Other methods estimate body fat percentage and use this value to suggest whether an individual is overweight. These methods range from body fat calculators based on body circumference through to esimates of body fat from calipers using skin folds. More complicated methods include underwater weighing, bioelectrical impedance, and computerized topography.
Are there any units to the Body Mass Index?
Yes, the units are kg/m².
Which organisations use the Body Mass Index?
The U.S. National Heart, Lung and Blood Institute and National Institutes of Health, and the World Health Organization recommend the body mass index to classify obesity.
Is the body mass index a better predictor than body fat?
Although body mass index is useful because it is easy to measure it has been shown in a recent publication that body fat may be a better method to evaluate obesity (see Ten-year comparison of BMI, body fat, and fitness in the workplace, Am J Ind Med 2006 49(4) 223-230 and Relationship between adiposity and body size reveals limitations of BMI, Am J Phys Anthropol. 2006 129(1) 151-6.)

[D-Nuck]

What are the dangers of extra weight?
Extra weight can put you at higher risk for these health problems - type 2 diabetes (high blood sugar), high blood pressure, heart disease and stroke, some types of cancer, sleep apnea (when breathing stops for short periods during sleep), osteoarthritis (wearing away of the joints), gallbladder disease, liver disease and irregular menstrual periods.

Does it matter if its fat weight or muscle weight??????-- i am confused

[MikeB]

Absolutely...

[D-Nuck]

it just says extra weight- whats the difference???

[MikeB]

Muscle is not considered extra weight, it's considered part of the lean body mass. It is healthy to have and helps burn calories. Fat is not, it just takes up resources to and drains off your body.
BTW for me to be "normal" with BMI I'd have to weight under 195lbs at 196lbs I'd be overweight. I can tell you there is no way in hell I'm getting to 195lbs...

[D-Nuck]

so what woudl you weigh if your BF was 6% wich would be lean and mean dude, espicially on 6'4 frame

[D-Nuck]

MASS is weight, reagrdless, your bones carry the wieght ,your heart and lungs provide O2 to the mass regardless, or am i wrong??

[MikeB]

Originally Posted by D-Nuck

so what woudl you weigh if your BF was 6% wich would be lean and mean dude, espicially on 6'4 frame

I'm approximately 190lbs muscle and bones only so at 6% I'd weigh 201.4lbs. I'm shooting for a more realistic 10% body fat so 210lbs. As I gain muscle my total weight will go up.

[MikeB]

Originally Posted by D-Nuck

MASS is weight, reagrdless, your bones carry the wieght ,your heart and lungs provide O2 to the mass regardless, or am i wrong??

Absolutely wrong, there is a huge difference between fat and muscle and the way it interacts with your body.
Here's another article to try and help explain it to you. Although I don't know how you can summarize that fat is the same as muscle...

Muscle vs. Fat
by author David Lige, BHK
Stepping on the scale is "over weighted." To determine healthy body composition, consider your percentage of body fat in proportion to muscle mass.
Understandably, many of us measure our ideal weight with a scale. Insurance companies and health professionals have used height versus weight scales (body mass indicators, or BMIs) for years to determine overall health. However, these are not always suitably informative because they fail to determine whether a person is muscled or fat.
Scales cannot differentiate between muscle and fat. You will obtain an accurate measurement of your weight, but you do not know how much is lean mass and how much is fat. Lean mass is simply your muscles, bones, connective tissue and organs. The remainder falls into the fat category. You do require a percentage of fat to function, but that consists of only about three per cent of your total body weight.
Studies indicate that, in terms of overall weight, most college-level football players are considered overweight and therefore more susceptible to health risks. In reality, this is far from the truth. The athletes are generally in excellent physical health but have a larger percentage of lean muscle mass.

Proportions Count

When determining your overall health, it’s important to consider your percentage of body fat in proportion to muscle mass. Someone weighing 200 pounds with a body fat percentage of 25 is carrying around 50 pounds of extra fat. That same person weighing 200 pounds with 10 per cent body fat would be carrying around only 20 pounds of fat. This is significant in terms of health, not to mention how exhausting it is to carry around 30 extra pounds of fat. In addition, the person with 50 pounds of fat has only 150 pounds of lean mass to carry that weight, whereas the person with 20 pounds of fat has 180 pounds of lean mass to sustain it. That factor alone will have a dramatic impact on energy level, joint stress and mobility.


THIS PORTION RIGHT HERE IS WHY I HATE DIET PILLS AND DIET SURGERY!!!
Thinner does not always mean healthier, either. Extremely thin people often have a lower-than-desired lean mass percentage. When we do not ingest enough calories, not only do we lose a percentage of our fat, we also diminish the percentage of lean mass. Starvation studies have indicated that parallel losses of lean mass and fatty tissue left subjects with the same percentage of body fat after weeks of starvation. In addition, our metabolic rates diminish as we reduce our percentage of lean mass. Our bodies require far more energy to move lean mass than to move fat. Remember, fatty tissue is an energy source and does not require energy to move. If we have a larger percentage of muscle mass, not only is it easier to move, but we also require more energy to do it. This is why exercise is so important in maintaining a healthy body type. Exercise and movement promotes the utilization of calories as well as the growth of lean muscle mass.

Measuring Up

Fat takes up more than four times as much space as lean muscle mass. So if you want to reduce your size, then reduce your percentage of body fat. An obvious indicator is your waistline. If your pants are becoming baggy but your weight is not changing too much, you know you are heading in the right direction.
Another way to determine body fat is by taking measurements. This is easy to do, cost effective and can be easily monitored. Use a tape measure and record your neck size, chest (just across the nipple line), upper arms around the biceps/triceps region, waist (just below the rib cage, slightly above the navel), thighs and calves. Where applicable, measure both sides of your body and, if possible, measure at the same time of the day. Do this regularly once a week to track your results.




For a professional opinion, have a skin fold measurement conducted. Skin fold measurements are taken by a skin fold caliper at different regions of the body. The caliper obtains an accurate measure of the percentage of body fat by measuring the layer of subcutaneous fat (just below the skin).

What’s Your Ideal Body Fat Percentage?

Remember, body mass index (height-weight) calculators can incorrectly suggest fatness in athletic or muscular people. Keeping this in mind, there is a standard ideal percentage of body fat, which differs between males and females. Use the above tests to better determine your proportion of muscle to fat.
The standard ideal percentage range of fat for males is 10 to 20 percent. Twenty to 25 percent is moderately high, 25 to 30 percent is high and 30 percent and above is considered obese. Females generally need a body fat measurement five to 10 percent higher than males. The ideal range for females is 15 to 25 percent. Twenty-five to 30 percent is moderately high, 30 to 35 percent is very high and above 35 percent is considered obese. Values exceeding 20 percent in males and 25 percent in females may lead to an increase in health problems such as diabetes, high blood pressure and heart disease.
By determining your percentage of body fat in proportion to lean muscle mass, you will have a clearer understanding of what you need to do to be fitand healthy. Do not get caught in the weight trap, but use it as a guide in your quest for health. If you have a high percentage of fat, your overall weight will diminish with a balanced diet and exercise, but remember to fuel those working muscles to increase mass. If you are looking to shed that extra 10 pounds, don’t get too caught up in how much you weigh, but consider your measurements, how you feel and how you look. The mirror is a good indicator of how much good and bad weight we carry. Remember, it is not how much you weigh, but rather what makes up the weight that counts.

The ideal percentage range of fat for males is 10 to 20 percent.

The ideal range for females is 15 to 25 percent.

Thinner does not always mean healthier, either. Extremely thin people often have a lower-than-desired lean mass percentage.

[D-Nuck]

ok i understand what your saying now-- but research suggests that people with a BMI over 29 or under 19 regardless of muscle or fat have a higher risk of chronic disease and premature death.. thats my point

[MikeB]

Originally Posted by D-Nuck

ok i understand what your saying now-- but research suggests that people with a BMI over 29 or under 19 regardless of muscle or fat have a higher risk of chronic disease and premature death.. thats my point

I'm saying that you can't make that assumption at all. Just because they have a specific BMI you don't know what their bodyfat percentage is and you are make a bad generalism.

If however you said that people with a bodyfat percentage over 25% are pre-disposed towards chronic disease and death you would be MUCH more accurate.

Let's look at this hypothesis:
People over 25% bodyfat have a high BMI (this is not necessarily true, there are "skinny fat people" out there too). The problem is not everyone with a high BMI is over 25% bodyfat. See the problem?

Same logic:
Women named Sue have red hair BUT not every Sue has red hair neither are all red heads named Sue.
Get it?

[D-Nuck]

HEALTH IMPLICATIONS OF OBESITY
With the rise in obesity levels in America over the past two decades, the impact of greater levels of obesity are beginning to be recognized in several health areas. It has been postulated that obesity causes approximately 300,000 deaths per year in America.16 The Surgeon General has warned that obesity related deaths could rival deaths caused by smoking in the near future.17 Individuals with a BMI of 30 kg/m^sup 2^ or greater comprised 80 percent of the deaths due to overweight or obesity.18 Individuals with BMI of 30 kg/m^sup 2^ have an increased mortality rate of 50 percent to 1OO percent from all causes, including cardiovascular disease, versus individuals with BMIs in the range of 20 to 25 kg/m^sup 2^.19
Obesity has been recognized as contributing to a number of health concerns including "hypertension, insulin resistance and diabetes mellitus, cardiovascular disease, hypertriglyceridemia, low high-density-lipoprotein cholesterol, and, in some studies, high total and low-density-lipoprotein cholesterol."20 Addition
FDCC Quarterly, Summer 2006 by Alford, Helen Johnson, Lampkin, James W II




Mike, weight is weight, mass is mass, muscle and fat have both. 50lbs of muscle puts the same stress on you bones as 50lbs of fat, they weigh the same dude,

you could be solid muscle with 2% BF and have a BMI of 32- do you agree thats possible or something close to it. This person could be a triathlete, NBA allstar, volunteer firefighter for all i care, it doesnt matter, what i am trying to say is that if your BMI >29 studies show you are more likely to gwt hypertension, cancer, diabetes, stroke, MI and die sooner, might not happen but likely it will.

"skinny FAT people" WTF is that, can you show me a pic- haha

BMI is measuring weight, not fat- if you have extra weight and its mostly comprised of FAT, then you really got something to worry about except whats for dinner!!!

overweight is over weight
over fat is over fat- GET IT???

[MikeB]

Originally Posted by D-Nuck

HEALTH IMPLICATIONS OF OBESITY
With the rise in obesity levels in America over the past two decades, the impact of greater levels of obesity are beginning to be recognized in several health areas. It has been postulated that obesity causes approximately 300,000 deaths per year in America.16 The Surgeon General has warned that obesity related deaths could rival deaths caused by smoking in the near future.17 Individuals with a BMI of 30 kg/m^sup 2^ or greater comprised 80 percent of the deaths due to overweight or obesity.18 Individuals with BMI of 30 kg/m^sup 2^ have an increased mortality rate of 50 percent to 1OO percent from all causes, including cardiovascular disease, versus individuals with BMIs in the range of 20 to 25 kg/m^sup 2^.19
Obesity has been recognized as contributing to a number of health concerns including "hypertension, insulin resistance and diabetes mellitus, cardiovascular disease, hypertriglyceridemia, low high-density-lipoprotein cholesterol, and, in some studies, high total and low-density-lipoprotein cholesterol."20 Addition
FDCC Quarterly, Summer 2006 by Alford, Helen Johnson, Lampkin, James W II




Mike, weight is weight, mass is mass, muscle and fat have both. 50lbs of muscle puts the same stress on you bones as 50lbs of fat, they weigh the same dude,

you could be solid muscle with 2% BF and have a BMI of 32- do you agree thats possible or something close to it. This person could be a triathlete, NBA allstar, volunteer firefighter for all i care, it doesnt matter, what i am trying to say is that if your BMI >29 studies show you are more likely to gwt hypertension, cancer, diabetes, stroke, MI and die sooner, might not happen but likely it will.

"skinny FAT people" WTF is that, can you show me a pic- haha

BMI is measuring weight, not fat- if you have extra weight and its mostly comprised of FAT, then you really got something to worry about except whats for dinner!!!

overweight is over weight
over fat is over fat- GET IT???

Absolutely WRONG, you couldn't be farther from the truth and that's the problem with people reading these BMI calculators and saying what you're saying. That a healthy muscular person is overweight due to their BMI score. Get real, all of my close friends are overweight or obese according to BMI due to their muscularity and most of them are/were national/world/olympic wrestlers.

I really can't believe that you think that overweight includes people who are in shape and carry muscle mass. It's ridiculous and unfortunately I can't help you learn the correct scenario for this except maybe go to your Dr. and spout your terrible understanding of this flawed calculation. I hope that you do not have a job at an insurance company because you would deny coverage for people like Jay Cutler or Ronnie Coleman or most of the world's college or olympic level athletes along with a majority of the physically fit/weight lifting crowd.

If you've never heard of skinny fat people it's a person who shows a normal BMI who is of "normal weight" but is over 20% bodyfat and is completely out of shape. Please try and watch Penn&Teller Bullshit!! Obesity episode. I already thought this way but it debunks the crap the government/weight loss industry is forcing down our throat right now.

I won't respond to any more of your posts on this, do the research and figure out how badly flawed your viewpoint is, please. Your saying that people who are overfat is overfat but also saying people with 2% muscle mass but over a BMI of 29 are the SAME. Bodyfat percentage is the more accurate way to calculate somebody's health, not BMI. By your thinking the people in this photograph are just as pre-disposed for health risks as a group of people who are over 20% bodyfat. All 3 of these guys are >29 BMI btw...

[Treasure]

MikeB, how accurate are the machines that calculate body fat and BMI? I just got an Omron fat loss monitor to use to track my progress. My BMI is slightly lower using the machine than it is using the website you linked above (34.9 v 35.4). I'm assuming the machine reading is more accurate?

[MikeB]

Well 1st ignore the BMI reading entirely and concentrate on bodyfat %. Unfortunately those meters are terrible. There are some decent calculators out there that you measure various body parts but the best way I've seen to tell bodyfat percentage is your abs.
You can look at your mirror and tell your bodyfat percentage!
Body Fat Percentage Guide for Men