Although excess weight can affect health, there is no one way to determine whether a person has overweight or obesity. There are different methods, each with its own pros and cons.

One of the common measurements is body mass index (BMI). It measures a person’s weight against their height.

However, this method does not distinguish between weight from fat and weight from muscle. This can mean people with high muscle mass and low body fat have an overweight BMI and vice versa.

Because of the limitations of BMI and other measurements for obesity, there is ongoing debate within the scientific community about the most accurate approach.

Keep reading to learn the different ways of determining whether a person has overweight, the advantages and disadvantages of each method, and more.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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According to the World Health Organization (WHO), “overweight” describes excess fat accumulation that presents a health risk.

However, the term is somewhat subjective. It lacks a precise, universally agreed-upon definition among medical experts.

This is because body weight and composition, and the effect this has on health, is relative. The higher a person’s weight, the more likely it is to affect their health, but the exact point at which excess weight becomes harmful for each person is difficult to pinpoint.

Calculating BMI involves using a mathematical formula: a person’s weight in kilograms (kg) divided by their height in square meters (m): BMI = kg / m2.

The result determines where it falls on a scale. The categories are:

  • Underweight: less than 18.5
  • Average weight: 18.5–24.9
  • Overweight: 25–29.9
  • Obesity: 30 or above

Limitations of BMI

Despite its widespread use, BMI has many limitations and criticisms.

The Belgian mathematician Adolphe Quetelet developed the BMI scale in the early 19th century. Originally, it was not a scale for measuring health. Quetelet wanted to calculate the physical characteristics of the “average man,” which he deemed to be the ideal humans should aim for.

To calculate this average, Quetelet mainly used data from white Europeans. As a result, the BMI scale’s definition of “average” only applies to one demographic. It does not consider potential differences in body types for people of different ethnicities and physical abilities.

Because Quetelet did not invent the BMI scale to assess health, this metric also does not consider the influence of muscle mass, bone density, and fat distribution, which can affect the results.

Athletes, for instance, may have overweight on the BMI scale due to their higher muscle mass despite having low body fat. Conversely, older adults may have lower BMIs due to a loss in muscle mass and bone density while still having higher body fat ratios.

Unlike BMI, RFM considers various factors to provide a more comprehensive understanding of body weight, including sex, height, and waist circumference.

Waist circumference can be significant because fat around the abdomen is a risk factor for various health conditions.

To measure RFM:

  1. Measure waist circumference in centimeters.
  2. Measure height in centimeters.
  3. Use a formula to calculate RFM. The RFM formula is RFM = 64 ? (20 × height/waist circumference) + (12 × sex). The value for “sex” is 0 for males and 1 for females.

Limitations of RFM

A 2023 study notes previous data has shown RFM is more accurate for males than BMI, but for females, it is about the same. As with BMI, misleading results are also still possible.

More research is necessary to validate RFM’s accuracy in diverse populations.

Body composition tells a person how much muscle, fat, and other types of tissue they have in their body. Several methods can calculate body composition, including:

  • Dual-energy X-ray absorptiometry (DEXA): DEXA scans use X-rays to provide a detailed breakdown of bone mineral density, lean tissue, and fat mass. It is one of the most reliable ways to measure body composition, but scans can be expensive.
  • Bioelectrical impedance analysis (BIA): This technology is what smart scales use to assess body composition. It works by measuring the resistance of electrical flow through different body tissues. It is a simple and quick test, but the results may vary depending on the scales and whether a person has consumed enough water. People with pacemakers cannot use BIA.
  • Hydrostatic weighing: This involves a healthcare professional taking two measurements. One is a person’s weight on land, and the other is their weight while sitting on a chair underwater. The difference between the measurements can tell practitioners a person’s body fat. It is very accurate but may not be accessible to everyone.
  • Skinfold thickness measurements: This involves using calipers, which are similar to tongs, to pull out and measure skin and fat around the abdomen. Skinfold thickness testing requires a skilled practitioner to get accurate results.

Body weight and composition are just one facet of metabolic health. Other metrics can provide more insights, such as:

Below are some answers to frequently asked questions about measuring overweight.

Can I have overweight and not look it?

Yes, it is possible for a person to have overweight without it being visually apparent. A person’s height, bone structure, and fat distribution all influence their body shape and appearance.

Some people may have a higher percentage of internal fat, making it less noticeable externally.

Am I overweight or chubby?

The term “chubby” is subjective and does not have a precise definition. Depending on how a person defines “chubby,” it is not necessarily distinct from overweight.

The best way to tell is by using evidence-based methods of measuring body weight, or by speaking with a doctor.

Does overweight cause symptoms?

No, overweight does not have any specific symptoms. It may only lead to symptoms if it contributes to another health condition, such as pain from pressure on the joints.

Anyone concerned or unsure whether they have overweight can speak with a doctor for guidance.

Whether they need answers to questions, to discuss weight changes, or support for weight management, a conversation with a doctor can help.

Being proactive ensures that people receive personalized guidance and timely interventions, fostering a comprehensive approach to overall well-being.

Measurements such as the body mass index (BMI) and relative fat mass (RFM) index can help people understand whether they have overweight. Body composition measurements such as DEXA and smart scales may also help.

However, each of these methods has its own advantages and limitations. Other metrics, such as cardiovascular fitness, may provide a more holistic insight into a person’s overall health than body weight alone.

Anyone concerned about whether they have overweight or obesity can consult a doctor for tailored guidance.