From the Guidelines
BMI, or Body Mass Index, is a numerical value calculated by dividing a person's weight in kilograms by the square of their height in meters, and it is used to categorize individuals as underweight, normal weight, overweight, or obese, with a BMI of 18.5-24.9 considered normal weight, 25-29.9 considered overweight, and 30 and above considered obese, as defined by the World Health Organization 1.
Definition and Calculation of BMI
BMI is calculated as weight in kilograms divided by height in meters squared, and it is a widely used screening tool to assess weight status and health risks associated with excess weight.
- BMI categories are defined as follows:
- Underweight: BMI < 18.5
- Normal weight: BMI = 18.5-24.9
- Overweight: BMI = 25-29.9
- Obese: BMI ≥ 30
Limitations and Considerations
While BMI is useful for population-level assessments, it has limitations for individuals, as it does not distinguish between muscle and fat or account for factors like age, sex, ethnicity, or body composition.
- For example, athletes with high muscle mass may have elevated BMIs despite low body fat.
- BMI should be considered alongside other health indicators like waist circumference, blood pressure, and blood glucose levels for a comprehensive health assessment.
Importance of BMI in Health Assessment
Despite its limitations, BMI remains valuable for identifying potential weight-related health risks and tracking weight changes over time.
- Regular monitoring of BMI, along with healthy eating and physical activity, can help maintain appropriate weight and reduce risk for conditions like heart disease, diabetes, and certain cancers.
- A person-centered communication style that uses inclusive and nonjudgmental language and active listening to elicit individual preferences and beliefs and assesses potential barriers to care should be used to optimize health outcomes and health-related quality of life 1.
From the Research
Definition and Calculation of BMI
- The body mass index (BMI) is calculated as weight in kilograms divided by height in meters squared 2
- BMI is used to classify individuals into different weight categories, such as underweight, normal weight, overweight, and obese 2
BMI and Health Outcomes
- A high BMI is associated with an increased risk of various health problems, including type 2 diabetes, hypertension, dyslipidemia, and sleep apnea 3
- BMI is also used as a risk factor for the development of certain health issues, such as cardiovascular disease and cancer 2
Bariatric Surgery and BMI
- Bariatric surgery is often considered for individuals with a BMI of 40 or higher, or 35 or higher with serious obesity-related comorbidities 3
- Studies have shown that bariatric surgery can result in significant weight loss and improvements in type 2 diabetes outcomes, regardless of the type of procedure used 3, 4
- Aerobic exercise combined with resistance training has been shown to be effective in increasing weight loss and decreasing BMI after bariatric surgery 4
Exercise and BMI
- Exercise training programs after bariatric surgery have been found to be effective in optimizing weight loss and fat mass loss, and improving physical fitness 5
- A systematic review and meta-analysis found that exercise training was associated with higher weight loss, higher fat mass loss, and improved VO2 max and functional walking after bariatric surgery 5