How is overweight and obesity diagnosed?

Overweight and obesity are conditions characterised by an excess accumulation of body fat, posing health risks.


In a world where lifestyles are fast-paced and convenience often takes precedence, the challenge of managing weight has become increasingly prevalent.

Overweight and obesity, once considered isolated concerns, now cast a significant shadow over global health.

Affinity Health shares information about how people can tell if someone is overweight or obese.

Murray Hewlett, the CEO of Affinity Health, mentions that the increasing problem of obesity is a worry in South Africa.

“Obesity is a growing concern in South Africa,” says Hewlett. 

“A study conducted by the South African Demographic and Health Survey in 2016 revealed the prevalence of overweight and obesity among adults in SA was estimated to be 68%, with around 28% classified as overweight and 40% as obese.

“Sadly, the World Obesity Federation anticipates an additional 10% increase (37%) in obesity among adults by 2030,” says Hewlett.

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Picture: iStock
Picture: iStock

Understanding the diagnostic criteria

According to Affinity Health, a Body Mass Index (BMI) is a numerical measurement that compares an individual’s weight to their height and is primarily utilised for identifying obesity.

To calculate a person’s BMI, a healthcare professional will:

  1. Use a scale to measure your weight in kilograms (kg).
  2. Use a measuring tape or a wall-mounted height rod to measure your height in metres (m).
  3. Divide your weight (in kilograms) by the square of your height (in metres). 

The diagnostic criteria for obesity using BMI are as follows:

  • BMI Below 18.5: Underweight
  • BMI 18.5 to 24.9: Normal weight
  • BMI 25 to 29.9: Overweight
  • BMI 30 or higher: Obese
  • Childhood Obesity Diagnosis

Detecting obesity in children and teenagers involves a comparable procedure, with certain adjustments to account for age and gender.

The diagnostic criteria for children and teens are as follows:

  • BMI Percentile Below 5th Percentile: Underweight
  • BMI Percentile 5th to 84th Percentile: Normal weight
  • BMI Percentile 85th to 94th Percentile: Overweight
  • BMI Percentile 95th Percentile or Higher: Obese
Picture: iStock
Picture: iStock

Additional assessments and considerations

It’s crucial to recognise that BMI has certain limitations. For example, it doesn’t account for factors such as muscle mass, bone density, or the distribution of body fat.

As a result, when healthcare providers diagnose and assess obesity, they may take into account other factors, such as:

  1. Waist Circumference: Measuring the waist circumference can help assess body fat distribution. A higher risk of health problems tied to obesity is linked to having extra belly fat.
  2. Health History: Healthcare providers evaluate a patient’s medical history, including obesity-related conditions such as type 2 diabetes, hypertension, heart disease, or sleep apnea.
  3. Lifestyle and Habits: Lifestyle factors, including diet, physical activity levels, and habits such as smoking and alcohol consumption, are considered when assessing obesity.
  4. Family History: A family history of obesity or related health conditions can increase an individual’s risk and may influence the diagnosis.
  5. Physical Examinations: Physical examinations may be performed by healthcare providers to examine overall health and look for indicators of obesity-related problems.
  6. Laboratory Tests: Blood tests may be ordered to measure cholesterol levels, blood glucose, and other markers that can provide insight into an individual’s metabolic health.
  7. Body Composition Analysis: In some cases, body composition analysis using methods like dual-energy x-ray absorptiometry (DXA) or bioelectrical impedance may be used to assess the proportion of lean body mass and body fat.
Picture: iStock
Picture: iStock

Why early diagnosis matters

Prompt identification of obesity is crucial for various reasons:

  1. Preventing Health Complications: Obesity is linked to various health problems. Early diagnosis allows for interventions to prevent or manage complications.
  2. Promoting Healthy Lifestyle Changes: Early detection enables people and families to implement healthy lifestyle adjustments, such as eating a balanced diet and increasing physical exercise, to avoid further weight gain.
  3. Access to Support and Resources: Early diagnosis ensures that individuals can access healthcare providers, dietitians, and other professionals who can provide guidance, support, and resources for weight management.
  4. Improved Quality of Life: Early detection and treatment of obesity can improve physical health, mental well-being, and general quality of life.
  5. Reducing the Economic Burden: Obesity places a significant economic burden on healthcare systems. Early diagnosis and intervention can help reduce healthcare costs associated with obesity-related conditions.

“Understanding the diagnostic criteria and assessments for obesity is the first step toward effective management and improved health outcomes.

“It’s essential for individuals to work closely with healthcare providers to develop personalised plans for weight management and overall well-being,” concluded Hewlett.

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