Definition of Obesity
Understanding What It Truly Means To Be Obese

The best definition of obesity used by doctors all over the world is "the accumulation of excessive body fat to an extent that it adversely affects the health and well being of the individual". The presence of excessive body fat or being overweight or obese is usually determined by measuring the amount of weight you carry for your height. This is called a measure of your BMI or body mass index. But what exactly does this mean to you as an individual? What are the grades or degrees of obesity and what treatment options exist for each grades or stages of obesity? Let’s find out here.

You are not obese simply because you weigh a lot. Obesity is about the amount of fat accumulated in the body in relation to your height. That is why you must not be quick to label yourself as obese, just because you weigh 180 pounds. If you are 6 feet tall, that may be a right weight for you! (BMI = 24.4).

Excessive amount of fat accumulation is dangerous.

To help decide when a person's weight is too much, various ways of estimating how "much fat is too much fat" has been developed. The most widely known of these measurements is the BMI (a short hand for Body Mass Index).

Other ways of measuring obesity include the use of :

  • Waist Circumference
  • Body Fat Calipers
  • DEXA Scans for Fat and Bone Density
  • Bioelectric Impendence Testing
  • Body fat MRI
  • Water Displacement Testing
  • Biopod

Many of these tests specifically aim to look at the percentage of body fat, rather than your actual weight.

The definition of obesity is based mostly on BMI measurement for uniformity. But what exactly is BMI and how can you determine the right BMI for you?

How To Calculate Your BMI

The Body Mass Index, also called the Quetelet index is a measurement which help to determine what weight is ideal for your height.

It is calculated by dividing your weight measured in kilograms by the square of your height measured in meters.

To calculate your BMI for example,

  1. Measure your weight in Kg, and height in meters. What did you get?
  2. Now multiply the value of your height by your height again to get your height squared (for example 1.8m X 1.8m = 3.24m)
  3. And then divide your weight (for example 80Kg) by the result (i.e. 80Kg ÷ 3.24 = 24.69).

So if you weighed 80kg, and you are 1.8meters tall, your BMI is 24.69 or 24.69Kg/m2.

Not used to calculations in kilograms and meters? No problem. You can calculate your BMI in pounds and inches easily too. To do that, follow the following steps:

  1. How much do you weigh in pounds? Multiply that by 703 (if you weigh 176 pounds for example, multiply this by 703, that is, 176 x 703 = 123,728
  2. How tall are you in inches? Multiply this by itself (if you are 70. inches tall, you multiply 70.866 x 70.866 = 5022)
  3. Now divide 123728 by 5022 (123728/5022 = 24.64)

So your BMI will be 24.64, which is a healthy BMI.

No time to fiddle with figures? You can use the BMI calculator here to calculate your BMI. You can chose to use the metric system (kg and meter or the imperial system - feet, pounds and inches options by clicking your choice of measurement inside the calculator (use the calculator to your right for 20 years and above only).

Defining Obesity On Waist Circumference

There is a strong relationship between our waist size and our weight. The larger the size above a certain range for a man or woman, the more likely he or she is obese. Measurement of waist gait or circumference is ONLY useful in those with a BMI of less than 30.

You can measure your waist circumference by using a standard measuring tape. To get the correct weight circumference measurement, you need to know the right landmark to start from. Find the midway between your lowest rib bone on the sides and the top of your hip bone. This is usually at a level just above your umbilicus or belly button. Measure the diameter of your waist at that level.

Measure your waist circumference now and note down the value and decide, using the information below, your likely weight situation.Yes. The definition of obesity and overweight could be based on the size of your waist!

Medical Definition Of Obesity & Interpreting BMI

The standard medical definition of obesity is based on BMI value. There are three grades of obesity. Each of these grades reflect the severity of this condition and this in turn is a strong indicator of complications that could arise from being in that class of obesity.

The National Institute for Health and Clinical Excellence (NICE) in the United Kingdom and National Heart, Lung, and Blood Institute (NHLBI) of the United States of America no longer defines obesity in terms of severely obese and morbidly obese, but prefers to classify obesity based on BMI, waist circumference and associated disease risk as:

  • Overweight
  • Obesity Grade I
  • Obesity Grade II
  • Extreme Obesity or Obesity Grade III

Interpreting BMI

The following are what a BMI could be telling us:

  • BMI less than 15 = Severely Underweight
  • BMI 16 to 18.4 = Underweight
  • BMI 18.5 to 24.9 = NORMAL
  • BMI 25 to 29.9 = Overweight
  • BMI 30 to 34.9 = Obese
  • BMI 35 to 39.9 = Grade II Obesity
  • BMI 40 and above = Grade III (morbidly) obese

Let's take a look at what each of these mean for the individual and the dangers they pose, as well as treatment options.


In the definition of obesity, with overweight being in that spectrum as mentioned above, you are considered medically or scientifically overweight if:

  1. Your BMI is anywhere between 25 to 29.9 and or if
  2. Your waist circumference is more than 40 inches (102cm) in men and over 35 inches (88cm) in women.

Your risk of developing complications start to increase at this point (actually starts to manifest from a BMI of 27)

If you get onto moderate exercise, dieting and lifestyle modification at this stage, you are most likely to succeed in conquering this emerging dangerous disease called obesity with its crippling effects.

You will only require the use of medications or weight loss pills prescription by your doctor at BMI of 27 to 30 ONLY if you have already develop a complication of obesity.

Grade I Obesity

Grade I obesity used to be termed simply as being obese in the old definition of obesity. You are said to be have Grade I obesity if:

  • Your BMI is between 30 - 34.9

Your risk of developing diabetes at this level dramatically increases from 5 to 9 fold! So too is your risk of developing high blood pressure, high blood cholesterol, heart attack, stroke, and snoring at night, and not enjoying your sleep making you feel sleepy during the day.

You need firm action here. Moderate to high intensity exercise, obesity diets, and lifestyle modifications as well as the introduction of weight loss pills is advocated to overcome obesity at this level.

Grade II Obesity

Grade two or grade II obesity is what used to be referred to as severe obesity in the old definition of obesity. You are said to have a grade two obesity if:

  • Your BMI is anywhere between 35 - 39.9

At this level of obesity, it is most likely that some of the health risks of obesity have started to manifest. They may include, at this stage, high blood pressure, diabetes, joint pain, snoring at night, low energy levels, low self esteem and depression.

Low to moderate intensity exercises, dieting and the use of prescription pills for obesity is required, along with compulsory lifestyle modifications.

Where any major co-morbidity or complications of being overweight like diabetes is noted, bariatric surgery like gastric banding is needed alongside the above measures (lifestyle modifications, diet, exercise programs).

Grade III Obesity

Grade three obesity or grade III obesity used to be referred to as morbid obesity. The term morbid obesity was dropped, as it is seen as a prejudging definition of obesity at this level. While it is true that many people with this grade of obesity would have complications, it is better to see this individuals and assess them on personal basis if they really have developed a morbidity or complication.

Grade 3 obesity is defined by a BMI of:

  • 40 or above

The risk of developing type 2 diabetes increases by up to 50 times at this stage of obesity.

Other potential health risks of obesity that can be developed at this stage include cancer of the gullet, breast, prostate, colon, stomach, heart attack, stroke, and a vast list of other complications including social stigmatization and isolation.

Treatment choice? Diet, life style modifications, low intensity exercises, and bariatric surgery.

If your BMI is within this range, do not procrastinate; see your doctor. Never give up hope or despair. Many with BMI of 62 and over have had successful treatment and regained their normal weight (BMI less than 30) after treatment, under qualified medical supervision. So pick up your phone now, and ring your doctor for an appointment.

Do not let your perception or indeed definition of obesity be determined by your friends or comments made by other people. If you suspect that you have any of the grades of obesity described above, go and see your doctor. Start addressing the issue with expert support from a trained medical personnel. Don't suppose it is all your fault and that you should handle this problem yourself. You may be surprised by the amount of assistance you could get out there. Without any doubt in my mind, you can conquer and overcome your obesity. Honestly.

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