What BMI is considered obese?

BMI is a common tool used to assess the nutritional and health status of the body based on weight and height. The obesity BMI threshold is closely related to an increased risk of serious chronic diseases such as diabetes, cardiovascular disease, and certain cancers. So what BMI is considered obese?

1. What is BMI? How is it calculated?

BMI (Body Mass Index) is an index widely used worldwide to assess a person’s nutritional status, from underweight to obese, based on the relationship between weight and height. The BMI calculation formula and classification thresholds are usually defined by international and national health organizations.

BMI calculation formula: BMI = Weight (kg) / (Height (m) * Height (m))

BMI classification according to WHO (World Health Organization): WHO is one of the reputable organizations that has set out BMI classification thresholds as follows:

• Below 16.0: Grade III thinness (Very thin, dangerous)
• 16.0 – 16.9: Grade II thinness (Moderately thin)
• 17.0 – 18.4: Grade I thinness (Mildly thin)
• 18.5 – 24.9: Normal (Ideal weight)

BMI classification according to Asian standards (WHO/IASO/ITO): Because Asians tend to have a higher body fat percentage compared to Europeans at the same BMI level, WHO has set specific classification thresholds for Asians:

• Below 18.5: Underweight
• 18.5 – 22.9: Normal
• 23.0 – 24.9: Overweight

BMI classification in Vietnam: In Vietnam, health agencies usually apply the WHO’s Asian BMI obesity classification standard with similar classification thresholds as above.

Other organizations: CDC (Centers for Disease Control and Prevention) uses obesity BMI thresholds similar to WHO but focuses on recommendations for obesity prevention, especially in children and adolescents.

However, it should be noted that BMI is a general index and does not fully reflect a person’s health status, as BMI does not consider muscle-fat ratio, fat distribution, or other factors such as lifestyle and general health condition.

2. What BMI is considered obese?

BMI is widely used to assess health risks associated with being overweight and obese. Below are the BMI thresholds as determined based on research and recommendations from major health organizations:

2.1. World Health Organization (WHO)

The WHO has conducted extensive research across different populations and established BMI thresholds for obesity based on the risk of developing chronic diseases such as type 2 diabetes, cardiovascular disease, and other metabolic disorders.

• BMI from 25.0 to 29.9: Overweight – At this level, the risk of developing weight-related diseases starts to increase but is not as high as in those who are obese.
• BMI of 30.0 or higher: Obesity – The risk of developing chronic diseases significantly increases when BMI reaches or exceeds this threshold. Obesity is further categorized into three levels:
  • Obesity Class I (BMI from 30.0 to 34.9): Increased risk, but at a mild level.
  • Obesity Class II (BMI from 35.0 to 39.9): Higher risk, potentially leading to serious health issues.
  • Obesity Class III (BMI of 40.0 or higher): Also known as “morbid obesity,” with extremely high health risks.

Additionally, numerous studies have confirmed the link between high BMI and the risk of chronic diseases:

• Framingham Heart Study (USA): One of the largest long-term studies on cardiovascular health has shown that the risk of developing cardiovascular disease increases significantly when BMI exceeds 30.
• Diabetes Research: Studies across various populations have shown that the risk of type 2 diabetes doubles in those with a BMI between 25 and 30 and increases 5-10 times in those with a BMI over 30.
• Cancer Research: Studies indicate that a high BMI is also associated with an increased risk of certain types of cancer, including breast, colon, and uterine cancers.

2.2. BMI thresholds for Asians

The WHO has adjusted BMI thresholds for Asians based on research indicating that Asians tend to have higher body fat percentages at the same BMI levels compared to Europeans. This leads to higher health risks for Asians even at lower BMI levels.

• BMI from 23.0 to 24.9: Increased risk (Pre-obesity) – Although not classified as obesity, Asians in this range already have a higher risk of obesity-related diseases.
• BMI of 25.0 or higher: Obesity – Considered obese with a high risk of chronic diseases.

Genetic studies have also shown that not everyone with a high BMI has the same risk of disease. Some people may have a high BMI but a lower body fat percentage, or vice versa. However, BMI remains a useful tool for assessing health risks at the population level.

A BMI of 30 or higher is considered the threshold for obesity, associated with a high risk of several serious chronic diseases. For Asians, this threshold may be lower, with Asian obesity starting at a BMI of 25 or higher. This reflects differences in body structure and fat distribution between different populations. However, it is important to note that BMI is only one of many indicators used to assess overall health.

3. How to Maintain an Ideal BMI?

Maintaining an ideal BMI is a crucial part of overall health and preventing chronic diseases. To achieve and maintain an ideal BMI, it’s essential to adopt healthy habits in diet, exercise, and lifestyle.

3.1. Healthy Diet

• Portion Control: Limit the amount of food consumed, especially high-calorie foods like sweets, fried foods, and sugary drinks.
• Eat More Vegetables and Fruits: Vegetables and fruits are rich in fiber, vitamins, and minerals, and are low in calories. They help you feel full longer, reducing the need to consume excess calories.
• Choose Healthy Protein Sources: Opt for lean meats, fish, eggs, beans, nuts, and low-fat dairy products. Protein helps maintain and build muscle mass and effectively controls hunger.
• Reduce Sugar and Salt Intake: Avoid processed foods high in sugar and salt, as they can contribute to weight gain and other health issues like high blood pressure and diabetes.
• Drink Plenty of Water: Water helps the body function efficiently and can control appetite. It’s recommended to drink at least 8 glasses of water daily to stay hydrated.

3.2. Regular Physical Activity

• Consistent Physical Activity: Engage in at least 150 minutes per week of moderate-intensity aerobic activities, such as brisk walking, cycling, or swimming.
• Strength Training: Incorporate strength training exercises at least twice a week to maintain muscle mass and boost metabolism.
• Daily Movement: Increase daily physical activity by walking more, using stairs instead of elevators, or participating in recreational activities like dancing or hiking.

3.3. Monitor Weight and Adjust Promptly

• Regular weigh-ins: Monitor your weight regularly, such as once a week, to track your progress and make adjustments to your habits if necessary.
• Waist Measurement: Waist circumference is also an important indicator, as abdominal fat is closely linked to the risk of cardiovascular diseases and diabetes.

3.4. Develop Long-term Eating and Lifestyle Habits

• Planned Eating: Plan your meals and groceries for the week to avoid uncontrolled eating.
• Build a Healthy Lifestyle: Focus on lifestyle changes rather than short-term dieting. Small, sustainable changes are easier to maintain and have long-lasting effects.

Additional Tips to Maintain an Ideal BMI:

• Stress Management: Practice relaxation techniques to reduce stress.
• Adequate Sleep: Get 7-9 hours of sleep each night to help your body recover and maintain hormonal balance. Lack of sleep can lead to weight gain and poor appetite control.
• Nutritional Counseling: If necessary, consult a nutritionist for advice and to create a personalized diet plan.
• Support Groups: Joining weight loss or healthy lifestyle support groups can provide motivation and encouragement.

By maintaining a balanced diet, regular physical activity, and effective stress management, you can keep your BMI within an ideal range and protect your overall health. If you experience health issues related to being overweight, it’s important to explore appropriate solutions for early treatment, as proactive health care is the best way to live a long and healthy life.

Nguồn:  cdc.gov – who.int – nhs.uk