What is BMI?
BMI is a number that shows how your weight compares to your height. It is determined by dividing your weight in kilograms by your height in meters squared. For example, if you weigh 70 kg and stand 1.75 m tall, your BMI is:
BMI = 70 / (1.75 x 1.75) = 22.86
You can also use our online BMI calculator to get your BMI and weight category. You can enter your weight and height in several units, including pounds, feet, and inches.
What is the normal BMI range?
BMI categorizes your weight status as underweight, normal, overweight, or obese. These classifications are based on the health hazards associated with various amounts of body fat. The table below illustrates adults' BMI ranges and categories according to the World Health Organization (WHO).
| BMI Range (kg/m2) | Weight Category | Health Risk |
| Less than 18.5 | Underweight | Increased risk of malnutrition, osteoporosis, and other health problems |
| 18.5 to 24.9 | Normal | Low risk of weight-related health problems |
| 25 to 29.9 | Overweight | Increased risk of high blood pressure, high cholesterol, diabetes, and other health problems |
| 30 or more | Obese | High risk of heart disease, stroke, cancer, and other health problems |
The BMI ranges and categories may vary slightly depending on the source and the population. For example, some Asian countries have lower BMI cutoffs for overweight and obesity, as they have higher health risks at lower BMI levels.
What are the limitations and alternatives of BMI?
BMI is a simple and convenient tool to estimate your body fat and weight status, but it has some limitations and drawbacks. Some of the limitations and alternatives of BMI are:
- BMI does not measure body fat directly but estimates it based on weight and height. Therefore, it may not be accurate for people with a lot of muscle mass, such as athletes, or a lot of bone mass, such as older adults. In these cases, a body fat calculator or a body fat scale may be more beneficial to measure your body fat percentage and lean body mass.
- BMI does not account for body fat distribution, which can affect your health risk differently. For example, having more fat around your waist (abdominal obesity) can increase your risk of heart disease and diabetes more than having more fat around your hips (gluteal obesity). In these cases, a waist-to-hip ratio calculator or a waist circumference measurement may be more beneficial to assess your abdominal fat and health risk.
- BMI does not account for other factors that impact health and weight, such as age, gender, ethnicity, lifestyle, and medical conditions. For example, when people get older, they lose muscle and gain fat mass, lowering their BMI but increasing their health risk. Women typically have more body fat than men, which might influence their BMI and weight category. To compare your BMI to the average values for your age and gender group, consider using a BMI chart for men or women.
- BMI does not indicate your optimum body weight or weight loss goals. For example, if you are overweight or obese, you may want to know how much weight you should reduce to get a normal BMI or healthy weight. In certain circumstances, an ideal body weight calculator or a weight loss calculator may be more helpful in determining your target weight and calorie consumption.
Limitations of BMI
Although BMI is a popular and effective predictor of healthy body weight, it does have some limits. BMI is merely an estimate and does not take body composition into account. Due to the broad range of body types and the distribution of muscle, bone mass, and fat, BMI should be used with other metrics rather than as the single tool for establishing a person's healthy body weight.
In Adults:
BMI is a measurement of excess body weight, not excess body fat, so it cannot be completely accurate. BMI is also influenced by age, gender, ethnicity, muscle mass, body fat, and activity level. For example, older people considered healthy but inactive in their daily lives may have a significant amount of excess body fat, even though they do not weigh much. It is considered unhealthy, whereas younger people with higher muscle composition and a similar BMI are healthy. Athletes, especially bodybuilders, may be considered overweight because muscle weighs more than fat, but there's a good chance they're at a healthy weight relative to their body composition.
According to the CDC, older adults tend to have more body fat than younger adults with the same BMI.
- Women tend to have more body fat than men of the same BMI.
- Muscular people and well-trained athletes may have a high BMI because they have more muscle mass.
In Children
- The same variables that restrain the legitimacy of BMI for adults may also apply to children and teenagers.
- Also, stature and genderual development can impact a child's BMI and body fat rate.
- BMI could be a way better indicator of body fat abundance in corpulent children than in overweight children.
- BMI can be due to expanded fat or incline body mass (all body components other than fat, counting water, organs, muscle, etc.).
- For lean children, contrasts in BMI may also be due to incline body mass.
- It is effectively used with other measurements to determine a person's healthy weight.
Conclusion
The BMI is a calculation of body fat based on height and weight. It is a simple and effective tool for assessing your health and weight, but it has certain limitations and drawbacks. BMI should be used as a general guideline, not as a definitive measure of your health and weight. You should also speak with your doctor or a nutritionist to get a more complete assessment of your health and weight.
Reference:
- https://en.wikipedia.org/wiki/Body_mass_index
- "BMI Growth Charts for children and young adults". US Centers for Disease Control and Prevention. 31 January 2019.
- Calculate Body Mass Index