Understanding Body Mass Index (BMI)
Body Mass Index (BMI) is a simple and widely used tool to estimate whether a person has a healthy weight for their height. It's calculated by dividing a person's weight (in kilograms) by the square of their height (in meters). BMI provides a general guideline for weight categories, helping individuals and healthcare professionals assess potential health risks associated with being underweight, overweight, or obese.
How BMI is Calculated:
The formula for BMI is:
BMI = weight (kg) / [height (m)]²
For example, if someone weighs 70 kg and is 1.75 meters tall, their BMI would be calculated as follows:
BMI = 70 / (1.75 * 1.75) = 70 / 3.0625 = 22.86 (approximately)
BMI Weight Categories:
The World Health Organization (WHO) and other health organizations generally categorize BMI as follows:
- Underweight: BMI less than 18.5
- Normal weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25 and 29.9
- Obesity Class I: BMI between 30 and 34.9
- Obesity Class II: BMI between 35 and 39.9
- Obesity Class III (Severe Obesity): BMI 40 or greater
Why BMI Matters:
Maintaining a healthy BMI is important because it's linked to a reduced risk of several chronic diseases, including:
- Heart disease and stroke
- Type 2 diabetes
- Certain types of cancer
- High blood pressure
- High cholesterol
It's crucial to remember that BMI is a screening tool and not a diagnostic tool. It doesn't account for muscle mass, bone density, or body composition. Therefore, while useful, it should be interpreted in conjunction with other health indicators and discussed with a healthcare professional.
function calculateBMI() {
var weightInput = document.getElementById("weight");
var heightInput = document.getElementById("height");
var resultDiv = document.getElementById("result");
var weight = parseFloat(weightInput.value);
var height = parseFloat(heightInput.value);
if (isNaN(weight) || isNaN(height) || height <= 0) {
resultDiv.innerHTML = "Please enter valid numbers for weight and height. Height must be greater than zero.";
return;
}
var bmi = weight / (height * height);
var bmiRounded = bmi.toFixed(2);
var category = "";
if (bmi = 18.5 && bmi = 25 && bmi = 30 && bmi = 35 && bmi <= 39.9) {
category = "Obesity Class II";
} else {
category = "Obesity Class III (Severe Obesity)";
}
resultDiv.innerHTML = "Your BMI is:
";
}
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