What is obese BMI? And what does BMI measure?

If you’re struggling with your weight, you may be wondering about obesity. How, exactly, is it determined whether you’re overweight or obese? And how is obesity measured?

Your BMI is a great indicator of whether or not you’re obese. There are a few things you may not know about BMI, including:

  • What does BMI measure?
  • How do you know if you’re overweight or obese?
  • What is the obese BMI?

If you’re trying to get a handle on your weight, read on to find out all you need to know about BMI and obesity.

What is Obesity BMI?

If you’re familiar with BMI, you already know that it’s a measure of your weight as compared to your height. If you don’t know your own BMI, you can easily calculate it. You’ll find instructions for doing so on our article about BMI calculations.

If this is the first time you’ve calculated your BMI, you may be confused by the number. For those of you who aren’t familiar, there are ranges to BMI, or body mass index. The range into which you fall is a good determination of your overall health. Those ranges are:

  • BMI < 18.5 = Underweight
  • BMI 18.5 to 24.9 = Normal, healthy weight
  • BMI 25 to 29.9 = Overweight
  • BMI > 30 = Obese

So, as you can see, the “obesity BMI” is considered anything that’s over 30.

This may be surprising to you. After all, you look good in your clothes, and you feel healthy. How can you be overweight, or obese?

Well, to answer that question, let’s look at the actual definition of obesity.

What is Obesity?

Everyone’s got fat. Everybody. Without fat, you couldn’t survive. A normal amount of body fat:

  • Maintains healthy skin and hair
  • Is essential for the absorption of vitamins from food
  • Ensures that your cells function and reproduce properly
  • Helps protect your immune system
  • Helps to regulate your fertility, or menstrual cycles in women
  • Protects your bones and muscles
  • Helps to regulate your body temperature, preventing overheating and hypothermia
  • Protects your internal organs

As you can tell, it’s very important to have some body fat! That’s why there’s a range of healthy BMI, as compared to too little or too much body fat.

Obesity is the accumulation of too much body fat. When you have too much body fat, the benefits listed above begin to subside, and are replaced by some dangerous side effects.

  • Increased risk of depression
  • Decreased absorption of vitamins
  • Increased risk of heart attack and stroke
  • Higher likelihood of developing Type 2 diabetes
  • Higher risk of cancer
  • Excess strain on joints and muscles
  • Increased risk of arthritis and joint disease

So, while it’s true that you can’t live without some body fat, there’s certainly such thing as too much.

What’s the Difference Between Being Overweight and Being Obese?

Being overweight vs being obese is actually a fine line. As you can see from the chart above, the difference (in BMI) between an overweight person and one who’s obese can be as small as .1 in BMI.

The reason that chart was developed is because there are definitely health risks that come into play with people with a BMI of over 30. While someone who’s overweight may experience high blood pressure and depression, obesity means an increased risk of life-threatening diseases.

While a person who is overweight can usually “fix it” with a good diet and a healthy amount of exercise, an obese person may require more drastic measures – even surgery.

And the cause of the problem can vary, too. People who are overweight are usually so because of genetics and food consumption. But people who are obese usually have other factors contributing. Psychological disorders, hormonal imbalances and extreme lethargy are just a few of those factors.

So, while there’s very little difference, numbers-wise, between being overweight and being obese, there are some very real health issues at play when you consider the other differences.

What are the Limits for Obese BMI?

BMI is a scale. On the low end of the scale, you have the underweight crowd. In the middle is the normal range. Then the overweight, then the obese. Finally, at the far end of the scale are the morbidly obese.

The minimum obese BMI is considered to be 30. That means that if you calculate your BMI at 30, you’re considered obese. At 29.9, you’re not.

There’s a maximum, too, though. At the top of the obese BMI scale is 39.9. If your BMI increases to 40 or more, you’re actually considered morbidly obese.

We’ll talk about the definition of morbidly obese in a minute. But, now that you understand the limits for obese BMI, you have a better idea of whether your own BMI is putting you at risk for health conditions.

If you’re in the obese or morbidly obese range, you are, in fact at a greater risk for all of the complications we listed above. It’s best to speak with your doctor as soon as possible to determine what measures you should take to lose weight.

Where does the BMI go from obese to morbidly obese?

We determined that, as soon as your BMI hits 40, you’re considered morbidly obese. There’s also another way to determine whether you’re in this BMI range: if you’re 100 pounds over your ideal weight.

What’s ideal weight? It’s the weight you should be, given your height and your gender. There’s a simple formula to find your ideal weight.

If you’re a man, your ideal weight is 56.2 kilograms for the first 5 feet of your height. Then, for every inch after that, add 1.41 kilograms.

If you’re a woman, the numbers are slightly different. It’s 53.1 kilograms for the first 5 feet of your height. Then, add 1.36 kilograms for every inch after that.

So, for example, a woman who is 5 feet and 3 inches tall would have an ideal weight of 53.1 + 1.41 + 1.41 + 1.41. That’s 57.33 kilograms, or just over 126 pounds.

If your weight is over 100 pounds above this idea weight, you’re considered morbidly obese.

What Does Being Morbidly Obese Mean?

We’ve already covered the many, many health problems that can come along with being obese, and with being morbidly obese. You’re at a very high risk for Type 2 diabetes, heart attack, stroke and more.

But there are some other implications of morbid obesity. First, and most practically, you may not qualify for health or life insurance. Many companies will exercise their right not to cover you, as your obesity is a pre-existing condition.

Secondly, you may be at a higher risk for complications during surgery. This, of course, can make a big difference should you need a heart transplant or even if you’re in a car accident.

But it also makes a big difference if you’re considering weight loss surgery. You must be considered morbidly obese to qualify for weight loss surgery. But, as your surgeon will tell you, there are huge risks associated with it – and the mortality rate post surgery is also high.

Is it only fat that the BMI measures?

BMI is a fairly accurate way to measure your body fat, yes. But there are factors which influence just how accurate that number is.

First of all, your age is a factor. No children should rely on the BMI scale to determine morbid obesity or obesity BMI. Their bodies just grow in a different way than adults’ do, and BMI is not a good indicator of health. If you’re concerned about your child’s weight, speak with your pediatrician.

If you’re over 65, you may want to discuss your body weight with your doctor, too. Older adults’ BMI isn’t always a good indicator of health, as the way we carry fat changes naturally as we age.

If you’re pregnant, you should never rely on BMI. Right now, your baby and your internal organs are adding weight to your body. That weight is very rarely fat. However, if you were a healthy BMI prior to your pregnancy, that’s usually a good indication that you’ll have fewer complications like gestational diabetes.

Finally, some athletes BMI range will vary. Athletes whose bodies are comprised of a lot of lean muscle will naturally weigh more than the average person. After all, muscle is four times as dense as fat, and therefore it weighs more.

So, while BMI does measure your percentage of body fat, it’s also not infallible. With that said, if your BMI is 40 or higher, there’s very little chance that it’s due to muscle.

Whether you measure a 30 or a 40 on the BMI scale, it’s in your best interest to talk to a doctor or a nutritionist. Taking steps to control your weight now can help to prevent dangerous health conditions later.

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