BMI Calculator Classification of Obesity by BMI and Risk of Associated Diseases Obesity Severity BMI Disease Risk Underweight < 18.5 kg/m² Risk of other diseases Normal weight 18.5 – 24.9 kg/m² Normal Overweight 25 – 29.9 kg/m² Increased Obesity Class 1 30 – 34.9 kg/m² High Obesity Class 2 35 – 39.9 kg/m² Very high Obesity Class 3 ≥ 40 kg/m² Extremely high What Does BMI Mean? 20-25 – Normal, no health risk factors. 25-30 – Overweight, weight reduction recommended for better health (BMI up to 27 is normal for athletic men). 30-35 – Obesity, high health risk. 35 and above – Class 3 or higher obesity, specialist consultation and weight loss required. BMI and Health Risk by Age BMI (Age 18-25) BMI (Age 25+) Health Condition Health Risk Recommended Actions < 17.5 < 17.5 Anorexia (Nervous/Atharoxic) Present, high Treatment for anorexia, weight gain < 18.5 < 18.5 Underweight None 19.5-22.9 20-25.9 Normal state 23-27.4 26-27.9 Overweight Present, increased Weight reduction recommended 27.5-29.9 28-30.9 Obesity Class 1 Present, increased Weight reduction recommended 30-34.9 31-35.9 Obesity Class 2 Present, high Strongly recommended weight reduction 35-39.9 36-40.9 Obesity Class 3 Present, significantly high Strongly recommended weight reduction ≥ 40 ≥ 41 Obesity Class 4 Present, critically high Urgent weight reduction required Health Impacts of Weight Excess weight is a major risk factor for various serious health issues. According to the Centers for Disease Control and Prevention (CDC), being overweight can contribute to: High Blood Pressure (Hypertension) Dyslipidemia: Elevated LDL (bad cholesterol), low HDL (good cholesterol), and high triglycerides Type 2 Diabetes Cardiovascular Disease Stroke Gallbladder Disorders Osteoarthritis: Cartilage breakdown in joints Sleep Apnea & Respiratory Problems Increased Cancer Risk: Breast, colon, kidney, liver, gallbladder, and endometrial cancers Diminished Quality of Life Mental Health Concerns: Higher rates of depression and anxiety Chronic Pain & Mobility Challenges Increased Mortality Risk: Higher likelihood of early death compared to a healthy BMI A BMI under 25 kg/m² is generally recommended for optimal health, but professional medical consultation is crucial for personalized advice. Dangers of Being Underweight Low body weight also comes with health risks, such as: Nutritional Deficiencies & Anemia Higher Risk of Osteoporosis & Fractures Weakened Immune Response Impaired Growth & Development (in children & adolescents) Reproductive Health Challenges: Hormonal imbalances and fertility issues Increased Surgical & Post-Operative Complications Elevated Mortality Risk Unintentional weight loss may indicate underlying health issues or eating disorders like anorexia nervosa, making medical assessment essential. BMI Limitations Although BMI is widely used, it does not distinguish between muscle mass, fat, or bone density. In Adults: BMI does not directly measure body fat. Factors like age, sex, and ethnicity influence BMI. Elderly individuals may have excess fat even within a “normal” BMI range. Athletes with high muscle mass may have elevated BMIs despite being in excellent health. In Children & Teens: Growth patterns impact BMI accuracy. BMI is more effective in identifying obesity than overweight status in children. Despite its drawbacks, BMI remains a useful health indicator when combined with other metrics. How to Calculate BMI The formula varies based on the measurement system: Imperial System: BMI=703×weight(lbs)height2(in)BMI = 703 \times \frac{weight (lbs)}{height^2 (in)} Example (5’10”, 160 lbs): BMI=703×160702=23.0BMI = 703 \times \frac{160}{70^2} = 23.0 Metric System: BMI=weight(kg)height2(m)BMI = \frac{weight (kg)}{height^2 (m)} Example (1.778m, 72.57kg): BMI=72.571.7782=23.0BMI = \frac{72.57}{1.778^2} = 23.0 BMI Prime: A Relative Measure BMI Prime compares an individual’s BMI to the upper healthy BMI limit (25 kg/m²): BMIPrime=BMI25BMI_{Prime} = \frac{BMI}{25} Ponderal Index (PI): An Alternative to BMI The Ponderal Index (PI) is more effective for very short or tall individuals, as it adjusts for height more accurately than BMI: Imperial System: PI=height(in)weight(lbs)3PI = \frac{height (in)}{\sqrt[3]{weight (lbs)}} Example (5’10”, 160 lbs): PI=701603=12.9PI = \frac{70}{\sqrt[3]{160}} = 12.9 Metric System: PI=weight(kg)height3(m)PI = \frac{weight (kg)}{height^3 (m)} Example (1.778m, 72.57kg): PI=72.571.7783=12.9PI = \frac{72.57}{1.778^3} = 12.9 PI provides a more nuanced assessment, especially for individuals at extreme heights.