What's a Healthy BMI for Women

Why is getting a healthy BMI a better way to gauge your weight and fitness? Whether it's cellulite, batwings, saddlebags, love handles or stretch marks, nearly all women have some concerns about their weight or figure at some point in their lives. There are countless charts out there to help women determine what their ideal weight should be, but they tend to be inaccurate and don't take muscle mass and bone structure into consideration. Therefore, women and health care professionals have turned to a more scientific method of deciding on a healthy weight: BMI, also known as body mass index.

What is BMI?
Your BMI is a calculation equal to your weight in kilograms divided by your height in meters squared. It was invented in the 19th century and has been in use since the 1950s as a way to determine whether an individual's weight is healthy or if they are height-weight proportional. The calculation is the same for both men and women -- who ever said life wasn't fair?

Men may not think so...
BMI calculations do not consider the makeup or distribution of your weight. That means that body fat percentage, muscle mass, gender and frame size, other than height, are not considered. Muscle is more dense than fat; it is common for athletes, bodybuilders and even people who are naturally muscular to have a BMI in the overweight or obese range even though they are extremely fit. Men are naturally more muscular than women, so men's BMIs may also be higher than that of women who are approximately the same size overall. However, they are still judged according to the same scale.

BMI ranges
Your BMI is just a number; if you have nothing to compare it to and no idea what "normal" should be, it's meaningless. Therefore, in 1998, the National Heart, Lung, and Blood Institute published a BMI guide in its "Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults." It identified five BMI ranges, including underweight (BMI less than 18.5), normal weight (BMI 20-25), overweight (BMI 25-30), obese (BMI 30-35) and morbidly obese (BMI 35+). These ranges are still the standard today.

Your BMI isn't normal: so what?
Everyone knows that being overweight can contribute to health problems such as diabetes, heart disease and strokes, right? And since your BMI tells you if you're overweight, having too high a BMI must be bad, right? Not necessarily. A study by the Mayo Clinic in 2006 actually debunked that theory. Researchers examined studies of over 250,000 patients and grouped them according to BMI, then analyzed their rates of disease and death, expecting that overweight, obese and morbidly obese people would be the unhealthiest groups. However, patients in the overweight and obese groups had the lowest incidence of both disease and death. Severely underweight individuals and the morbidly obese suffered the most.

Are there other guidelines?
According to a 2008 study by the Mayo Clinic, body fat percentage may be a better determinant of a person's health and health risks than BMI. Because BMI doesn't consider body composition, it is possible for women with a normal BMI to have an unhealthy amount of body fat. This condition is known as "normal weight obesity" or "over-fat." Ideally, women should have no more than 30 percent body fat.

Is there such a thing as too little fat?
Absolutely. Fat is essential for many bodily functions, and women need more of it than men. According to the American Council on Exercise, women should maintain a bare minimum of 10 percent body fat; anything less than that severely compromises fertility and other hormonal functions. Average body fat percentages for women range from 22-25 percent, with anything above 30 percent being considered obese.

Measure your fat, not your weight
Knowing your body fat percentage is smart for a number of reasons. Not only can it help you determine an ideal weight, but also it can guide you in your weight loss efforts and prevent you from losing too much weight. There are several ways to measure your body fat percentage, including calipers, home body fat scales and an immersion method called hydrostatic weighing. This last is the only truly accurate method, but even an estimate can help women decide on a healthy goal weight. For instance, if you are 150 pounds and 22 percent body fat, you have about 33 pounds of fat. If you wanted to lose 30 pounds but maintain your muscle mass, you would have only 2.5 percent body fat left, which is not only unrealistic, but dangerous as well.

Healthy BMI versus healthy weight
Due to the vague nature of BMI, doctors and health care professionals are now looking to other measurements for guidance in determining a healthy weight. In addition to overall body fat, waist measurement appears to be an important factor. A recent study published in the New England Journal of Medicine states that a waist measurement greater than 39 inches almost doubles the risk of death from heart disease for women. Also, the lower you carry your weight, the better - women who are pear shaped should stop cursing their hips and thighs. The ratio of waist to hips should be less than .85, with .7 or lower being optimal. This is for both health and beauty reasons -Sir Mix-a-lot of "Baby Got Back" fame will tell you that.

Healthy BMI versus vanity
All women have fat days, and most women struggle with their weight at one time or another. Additionally, there is a great deal of societal pressure on women to be as thin as possible, whether it's healthy or not. Despite its flaws, BMI is still a reasonably good way to determine a healthy weight range for most women, but it is not a hard and fast rule. If you are above the normal BMI range but you are not over-fat and you are happy with the way you look, don't sweat it. For health purposes, it is far more important to maintain a reasonable body fat percentage and hip-to-waist ratio. 

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