BMI Calculator: Manage Healthy Weight with Body Mass Index
What is BMI (Body Mass Index)?
BMI (Body Mass Index) is an international standard indicator for measuring obesity using height and weight. This index, devised by Belgian mathematician Adolphe Quetelet, is widely used worldwide because it can effectively evaluate an individual's weight status simply.
The calculation formula is weight (kg) divided by the square of height (m), BMI = Weight(kg) ÷ [Height(m) × Height(m)]. For example, for a person with height 170cm and weight 65kg, BMI = 65 ÷ (1.7 × 1.7) = 22.5.
BMI Standards (WHO Asia-Pacific Criteria)
The BMI standards for Asians, including Koreans, are stricter than those for Westerners. Even with the same BMI, Asians have higher body fat percentage and more abdominal obesity than Westerners, so the risk of metabolic diseases is greater.
- Underweight: Below 18.5 - Risk of nutritional deficiency
- Normal: 18.5 - 22.9 - Healthy weight range
- Overweight: 23.0 - 24.9 - Weight management needed
- Mild Obesity (Stage 1): 25.0 - 29.9 - Active weight loss recommended
- Moderate Obesity (Stage 2): 30.0 or above - Medical management needed
For reference, WHO Western standards have normal BMI of 18.5-24.9, overweight 25-29.9, and obesity 30 or above, which is higher than Asian standards.
BMI and Health Risks
When BMI deviates from the normal range, the risk of various health problems increases.
Underweight (BMI below 18.5)
- Nutritional deficiency, decreased immunity
- Increased risk of osteoporosis
- Anemia, irregular menstruation
- Decreased muscle mass
- Difficulty conceiving in women
Overweight and Obesity (BMI 23 or above)
- Increased risk of type 2 diabetes
- Hypertension, cardiovascular disease
- Dyslipidemia (hyperlipidemia)
- Fatty liver
- Sleep apnea
- Arthritis (weight burden)
- Increased risk of some cancers (colon cancer, breast cancer, etc.)
- Depression, decreased self-esteem
In particular, obesity with BMI 25 or above increases the risk of death from cardiovascular disease by 1.5-2 times, and the risk of developing diabetes is 3-7 times higher than normal weight.
Limitations of BMI
BMI is a simple and useful indicator but has some limitations:
- Does not consider muscle mass: Athletes or bodybuilders with high muscle mass may have high BMI but low body fat percentage. Muscle is heavier than fat, making it difficult to distinguish with BMI.
- Does not consider age: As age increases, muscle mass decreases and body fat increases, but BMI does not reflect this.
- Gender differences: Even with the same BMI, women tend to have higher body fat percentage than men.
- Fat distribution: Cannot distinguish between abdominal obesity (visceral fat) and subcutaneous fat. Abdominal obesity has a higher risk of metabolic diseases.
Therefore, it's good to comprehensively evaluate BMI along with waist circumference, body fat percentage, and blood tests.
Healthy Weight Management Methods
Balanced Diet
- Eat plenty of vegetables and fruits (5 or more times a day)
- Choose whole grains instead of refined carbohydrates
- Eat quality protein (fish, tofu, chicken breast)
- Reduce processed foods and fast food
- Avoid beverages containing sugar and liquid fructose
- Eat three regular meals a day
- Chew slowly and thoroughly
Regular Exercise
- Aerobic exercise: 150 minutes or more per week (brisk walking, jogging, swimming, cycling)
- Strength training: 2-3 times per week (maintains muscle mass to increase basal metabolic rate)
- Increase daily activity (use stairs, use public transportation)
- Avoid sitting for long periods and stretch every hour
Lifestyle Improvements
- Adequate sleep (7-8 hours per day)
- Stress management (meditation, yoga, hobbies)
- Quit smoking, moderate drinking
- Maintain regular daily rhythm
- Weight recording habit (measure 1-2 times per week at the same time)
Precautions When Losing Weight
- Avoid rapid weight loss (0.5-1kg per week is appropriate)
- Avoid extreme low-calorie diets (risk of yo-yo effect)
- Avoid single-food diets
- Reducing meals without exercise causes muscle loss
- Be careful not to go below BMI 18.5
Pregnancy and BMI
Pre-pregnancy BMI is an important criterion for determining recommended weight gain during pregnancy.
- Underweight (BMI below 18.5): 12.5-18kg increase recommended
- Normal (BMI 18.5-22.9): 11.5-16kg increase recommended
- Overweight (BMI 23-24.9): 7-11.5kg increase recommended
- Obese (BMI 25 or above): 5-9kg increase recommended
Maintaining appropriate weight before pregnancy helps prevent complications such as gestational diabetes, preeclampsia, and difficult delivery, and helps with healthy childbirth. If you're planning to become pregnant, it's good to adjust to an appropriate weight in advance.
Body Fat Percentage and Waist Circumference
Measuring body fat percentage and waist circumference along with BMI enables more accurate health assessment.
Body Fat Percentage Standards
- Men: 10-20% normal, 20-25% overweight, 25% or above obese
- Women: 18-28% normal, 28-33% overweight, 33% or above obese
Waist Circumference Standards (Abdominal Obesity)
- Men: 90cm or above
- Women: 85cm or above
If waist circumference exceeds the standard, there is a lot of visceral fat, so the risk of metabolic syndrome is high, and weight management is needed even if BMI is normal.