BMI, or body mass index, is a calculation that uses height and weight sometimes employed by healthcare providers as an indicator of your health. If you've never been approached by a health professional about your BMI, consider yourself lucky. BMI is primarily used to provide a risk factor estimate for the development of chronic disease, namely, Type 2 diabetes, heart disease, high blood pressure and certain cancers. According to a 2014 article published in BioMed Central Public Health, the risk of chronic disease increases with a higher BMI.
A low BMI is anything below 18.5. The research on the impact of a low BMI is not extensive, but that range is considered underweight. Genetically, you may be predisposed to having a low BMI, and, in this case, it may be difficult for you to gain weight. For older adults, a low BMI may indicate malnutrition and loss of lean body mass. According to a 2010 article published in the New England Journal of Medicine, being underweight may also put you at risk for higher chance of death. Research published in 2014 in BioMed Central Public agreed with this conclusion but also added that higher mortality risk in the underweight population can be caused by external factors, such as smoking, inability to recover from illness and depression.
A normal or good BMI is a measurement from 18.5 to 24.9. If you are in this range, aim to maintain your weight and current level of physical activity. The National Heart, Lung and Blood Institute recommends paying attention to your environment, physical activity level, behaviors and habits and calorie intake to keep your BMI within this healthy range. While it's not a guarantee, keeping yourself in the normal BMI category can also help lower your risk of chronic disease, such as high blood pressure, type 2 diabetes and heart disease, according to the National Heart, Lung and Blood Institute.
Having a BMI over 25 is considered overweight, while a BMI over 30 is considered obese. According to the Eunice Kennedy Shriver National Institute of Child Health and Human Development, 34 percent of U.S. adults are overweight, and 35 percent are obese. As BMI rises over 25, not only does the risk of common chronic diseases such as type 2 diabetes, cancer and heart disease increase, but so does the possibility of reproductive problems, joint pain, gallstones and breathing problems. Healthy lifestyle and dietary modifications can help lower a high BMI, and you can begin to reduce your risk of chronic disease.
Drawbacks to BMI
BMI ranges are a tool to estimate the risk of chronic disease. But BMI is not a direct measure of body fatness and is a more precise predictor of health when used in conjunction with another measurement, such as waist circumference: below 40 inches for men and less than 35 inches for women. Some individuals have excess muscle and would be considered overweight or obese with the current BMI calculation, but they are healthy. Moreover, if you fall in the normal BMI range because genetics favor you, you still cannot be absolute certaint that you are not at risk for chronic disease. BMI also does not incorporate age, frame size or gender into the equation.
How to Get a Good BMI
If you have concerns about your current BMI, it's best to consult a healthcare professional. They can lead you in the direction for weight gain, weight loss or maintenance and get you on the road to health. Other health conditions, medications or personal lifestyle habits may be preventing you from achieving a good BMI. A medical professional can provide resources or a referral to a registered dietitian nutritionist to evaluate your diet and current level of physical activity and make suggestions for a healthy change, if necessary.
- BioMed Central Public Health: Chronic Disease Burden Associated with Overweight and Obesity in Ireland: The Effects of a Small BMI Reduction at Population Level
- New England Journal of Medicine: Body-Mass Index and Mortality among 1.46 Million White Adults
- BMC Public Health: Mortality Risk Associated With Underweight: a Census-Linked Cohort of 31,578 Individuals With up to 32 years of Follow-up
- National Heart, Lung, and Blood Institute: Maintain a Healthy Weight
- Eunice Kennedy Shriver National Institute of Child Health and Human Development: How many people are affected by/at risk for obesity & overweight?