What Is BMI and Why Should I Know Mine?

BMI stands for body mass index. BMI measurement is essentially a tool to help doctors and patients assess patients’ height-to-weight ratios. Like any tool, it is not perfect. It is helpful, however, especially to diagnose obesity or morbid obesity.

It’s simple to check your own BMI. Simply use an online BMI calculator like ours. Enter your weight and height, and the calculator will provide your BMI result along with a range to help you determine into which category you fall.


If your BMI is less than 18.5, you are considered underweight. Being underweight can be just as stressful on your body as being overweight. Some health concerns for underweight people are as follows:

  • Weakening of the immune system
  •  Higher risk of osteoporosis
  •  Infertility

Being seriously underweight can lead to problems with your heart and other organs. Talk to your doctor about healthy ways to add weight, including increasing your caloric intake with healthy foods and strength training to develop lean muscle.


When your BMI is between 18.5 and 24.9, your weight is considered normal for your height. It is possible to have a normal BMI and have troubles associated with being overweight, including high cholesterol and type 2 diabetes. Eat a healthy diet and exercise regularly to stay within this range. Have regular checkups with your doctor to make sure your cholesterol and insulin levels are good.


If your BMI is 25 to 29.9, you are considered overweight. This category can be tricky and is the most difficult to interpret. One of the flaws of BMI measurement is that it only measures total weight. It doesn’t take into account your skeletal structure or your muscle mass. Since muscle is denser than fat, if you are fairly muscular you will weigh more than an average person of your height, even though you may look leaner. Professional athletes often have BMIs in the overweight category although they have hardly any fat on their bodies.

To help determine if you are truly overweight, your doctor will use a caliper to take a body fat reading. If you do in fact fall into this category, it’s time to consider a lifestyle change. Even a moderate amount of extra weight increases your risk for a number of health conditions, including stroke, heart attack and diabetes.


If your BMI is over 30, you are medically obese. As your BMI rises, your health risks are considerably greater. According to a study co-authored by the American Cancer Society and the National Cancer Institute and published in 2010 in the New England Journal of Medicine, one in three Americans over the age of 20 are obese. Approximately 17 percent of women and 11 percent of men are severely obese, with BMIs over 40.

One of the most frightening results of the study is that people with BMIs of 30 to 35 have a 44 percent increase in their risk of death, compared to people with BMIs in the normal range. People with BMIs between 35 and 40 increase their risk of death by 88 percent. Those with BMIs over 40 have an astonishing 250 percent increased risk of death. According to the study, these numbers remained static, regardless of other risk factors, including alcohol use and activity level.

Why is the increased risk of death so dramatic? A higher-than-30 BMI drastically increases your chances of developing the following serious health conditions:

  •  High blood pressure
  •  Stroke
  •  Heart disease
  •  Diabetes
  •  Difficulty breathing
  •  Certain types of cancer

While many people are aware of these risks, few are aware that a BMI in the obese range means tremendous kidney strain. One study found that nearly 35 percent of kidney disease could be prevented if obesity were not a factor. The same study found that the overweight people had a 40 percent increased risk of kidney disease compared to those with normal BMIs, and obesity meant an 83 percent higher risk.

If you are overweight or obese, work with your doctor to create a weight loss plan focused on a healthy diet and exercise plan. Reducing your BMI will reduce your risk of disease and early death.