What BMI Tells You About Your Health Status as an African

By: Temitope Oyetunji, MBBS, FWACP (Family Medicine). Medically reviewed by O. Oni, MD.

 

An illustrated BMI chart with color-coded weight categories and two boys, one slim and one overweight, standing on either side to represent different BMI ranges. Modified from a Freepik design, Click on image to enlarge.

 

Highlights

• Body Mass Index (BMI) is a simple screening tool that estimates body fat using weight and height.

• BMI categories include underweight, normal weight, overweight, and obese; each linked to varying levels of health risk.

• BMI is widely used because it is simple, cost-effective, and easy to calculate, making it a standard tool that many healthcare providers are familiar with.

• In Africans, BMI has its limitations as it does not account for differences in body composition and may not accurately reflect health risks in all individuals.

• Africans can complement BMI with other tools such as waist circumference, waist-to-hip ratio, and waist-to-height ratio for a more accurate assessment of health risks.

• Despite its limitations, BMI remains a helpful starting point. It can raise awareness, spark discussions with your healthcare provider, and guide you toward setting realistic health goals.

 

Introduction

Body Mass Index (BMI) is a widely used health measurement that estimates body fat based on a person's weight and height, and determines whether an individual has a healthy body weight.

The average Body Mass Index (BMI) in Africa is steadily increasing, contributing to a growing prevalence of overweight and obesity across the continent, particularly in Southern Africa, which reports some of the highest rates. [1, 2]

This article explores what BMI can say about your health status, its advantages and limitations as a screening tool, and what you can do with your BMI information as an African.

 

What Is BMI and How Is It Calculated?

Body Mass Index (BMI) measures the relationship between weight and height. Developed by Adolphe Quetelet in the 19th century for statistical studies, it has since become a popular and easy-to-use tool for checking whether a person’s weight is within a healthy range. [3]

It helps to determine whether a person is underweight, at a healthy weight, overweight, or obese. [4]

It is useful in assessing risk factors for certain health conditions, including heart disease, high blood pressure, or type 2 diabetes.

Body mass index is calculated by dividing a person’s weight (in kilograms) by their height squared (in metres). [4]

• BMI = weight (kg) ÷ height (m²)

For example, to calculate BMI for a 70kg person who is 1.7m tall,

• BMI = 70 ÷ 1.7²

This gives a BMI of 24.2kg/m²

You can calculate your BMI here

 

What Does BMI Tell You About Your Health?

Your Body Mass Index (BMI) offers more than just a number. It gives insight into whether your weight falls within a healthy range for your height. 

Here are the different BMI categories  [5, 6]:

• Underweight: BMI less than 18.5
• Healthy weight: BMI 18.5 – 24.9
• Overweight: BMI 25 – 29.9
• Obesity: BMI 30 and above

Here’s what different BMI categories generally indicate:

• Underweight (BMI less than 18.5): May signal poor nutrition or underlying health issues. In African settings, this could also be linked to malnutrition or chronic illness.
   
• Normal weight (BMI 18.5–24.9): Typically associated with a lower risk of weight-related diseases when combined with other healthy lifestyle habits.
   
• Overweight (BMI 25–29.9): Increases your risk for conditions like type 2 diabetes, high blood pressure, and heart disease.
   
• Obesity (BMI 30 and above): Significantly raises the risk for chronic illnesses including stroke, certain cancers, and joint problems. Obesity rates are rising across many African countries, especially in urban areas, due to changing diets and lower physical activity. [1, 2]

BMI thus serves as an essential screening tool for raising awareness about potential health risks associated with different weight categories. 

 

What are the Advantages of BMI?

In African healthcare settings, BMI plays an important role in health promotion and disease prevention. It has the following advantages:

• It is simple and cost-effective

BMI only requires the height and weight of an individual. It can be measured quickly with no special equipment or expensive tools needed. This makes it practical for low-resource African settings. [3, 7]

• It helps identify people with potential for chronic health risks

BMI can help flag people who may be underweight, overweight or obese. These are groups more likely to face health issues if not properly managed. Thus, its use encourages early lifestyle changes before diseases like diabetes, hypertension, and heart disease set in.

• It supports public health interventions

BMI is widely recognized as a standard tool to assess how body weight relates to the risk of health problems across large populations. [3]

With proper training, community health workers can accurately measure height and weight to calculate BMI at the community level. This data helps track health trends, monitor the burden of overweight and obesity, and inform national health strategies.

Governments and non-governmental organisations (NGOs) also rely on BMI to design health education campaigns, implement community-based interventions, and allocate resources effectively.

• It initiates meaningful health conversations

Even though BMI has its limitations, it is a useful starting point for patients and healthcare providers to begin discussing:

• Healthy weight goals
• Physical activity
• Dietary habits
• Other risk factors like
  • Smoking cessation
  • Alcohol use
  • Sleep hygiene and quality
  • Stress management
  • Etc.

Cartoon illustration of the advantages and limitations of BMI. Click on image to enlarge.

 

What Are the Limitations of BMI?

While BMI serves as a useful tool for identifying potential weight-related health risks, it does not directly measure body fat and should not be used on its own to diagnose overweight or obesity. [8] 

It should always be interpreted alongside other measurements and health indicators.

Below are some of the limitations of BMI:

• It does not account for body composition

BMI does not differentiate between muscle and fat. This means that a muscular person (like some athletes or farmers) may be classified as overweight or obese, even if their body fat is low.

A person with low muscle mass but high body fat may also appear to have a “healthy” BMI when they are actually at risk.

• It overlooks fat distribution

Where fat is stored matters. People who carry more fat around the abdomen (central obesity) are at greater risk for chronic diseases like diabetes and heart disease even if their BMI is “normal.”

For many Africans, waist circumference and waist-to-height ratio may be better indicators of health risk than BMI alone.

• Ethnic and genetic differences

Research suggests that people of African descent may have different body compositions compared to other ethnic groups. They are more likely to store fat around the abdomen (central obesity), which increases their risk of heart disease and diabetes even at lower BMI levels. [8]

This means using the same BMI cutoffs across all populations may not reflect true health risks for Africans.

• It does not reflect overall health

Another limitation of BMI is that it does not account for individual differences. Factors like genetics, lifestyle, environmental influences and diet can vary widely among people with the same BMI. 

Someone with a high BMI may have normal health markers like blood pressure, cholesterol, or blood sugar, while another with a normal BMI may have hidden health risks. This makes BMI an imperfect tool for assessing overall health on its own. [2]

 

Beyond BMI: Other Tools Africans Can Use to Monitor Health

BMI can be a valuable starting point for understanding your health risks, but it works best when considered alongside other measurements of the various dimensions of the human body and measures of body composition and fat distribution. 

 

A shirtless Black man wearing jeans measuring his waist with a tape measure against a blue background. AI generated from Freepik

 

These measures include: 

Waist Circumference

• This measures the size of your abdomen, and it is a practical method used to assess abdominal obesity. It is a reliable indicator of visceral fat (the type of fat stored around internal organs). [8. 9]
• It is a strong predictor of heart disease, diabetes, and stroke risk. [8]
• A waist circumference over 88 cm (35 inches) in women and 102 cm (40 inches) in men is considered high risk. [9]

Waist-to-Hip Ratio (WHR)

• This compares the circumference of your waist to that of your hips
• It is also an indicator of visceral fat and central obesity.
• The World Health Organization recommends a WHR cutoff of 0.8 for women and 1 for men. [9]

Waist-to-Height Ratio (WHtR)

• This is a measure of body fat distribution. 
• It is obtained by dividing your waist circumference by your height.
• Recent research shows that Waist-to-Height Ratio (WHtR) is a more accurate predictor of metabolic and cardiovascular risk than Body Mass Index (BMI) or Waist Circumference (WC) alone. [8]
• A WHtR of 0.5 or less is generally considered healthy for both men and women.
• A higher WHtR is strongly linked with increased risk of chronic health conditions such as type 2 diabetes, high blood pressure, unhealthy cholesterol levels, metabolic syndrome, and heart disease. [8]

Body Fat Percentage

• This measures how much of your body is made up of fat compared to lean mass (muscle, bone, water).
• Body fat percentage can be measured using various techniques, ranging from simple methods like skinfold measurements and bioelectrical impedance analysis (BIA) to more advanced methods like dual-energy X-ray absorptiometry (DXA) 
• Though more accurate, these techniques often require specialized equipment and tools which may not be readily available in many African healthcare settings.
   

What Can You Do With Your BMI Information?

Here's how you can use that number wisely to make better health choices:

Understand Your Risk

Your BMI category (underweight, normal, overweight, obese) can help you understand if you're at greater risk of health conditions such as:

• High blood pressure
• Type 2 diabetes
• Heart disease
• Certain cancers

But remember that it does not tell the full story. You should combine it with other measurements like waist circumference, waist to hip ratio and waist to height ratio to get a clearer picture.

Start a Conversation with Your Healthcare Provider

 

A black woman and her healthcare provider having conversation about her health. Image credit: Freepik

 

If your BMI is outside the normal range, don’t panic. Instead:

• Ask your doctor what the number means in your specific case.
• Discuss factors like diet, physical activity, and stress, which all affect your health.
• Get screened for other risk factors that BMI alone cannot detect. This includes your blood pressure, blood sugar and cholesterol levels.

Set realistic Health Goals

 

A plus-sized man exercising with dumbells. AI generated image from Freepik.

 

Use your BMI as a guide to:

• Make small, sustainable lifestyle changes like walking more or reducing sugary drinks.
• Aim for gradual weight loss or gain, if needed. 

Track Progress Over Time

Steps in monitoring progress. Click on image to enlarge.

 

BMI is not a one-time check. It can help you:

• Monitor your progress as you adopt healthier habits.
• Stay motivated when paired with other signs of improvement, like better sleep, more energy, or improved blood sugar levels.

 

Conclusion

Body Mass Index (BMI) provides a quick and easy way to assess your weight in relation to your height. It is a valuable screening tool that can highlight potential health risks and encourage conversations about healthy living. However, BMI alone does not capture the full picture of your health, especially for Africans, whose body composition and lifestyle can vary greatly

To get a more accurate understanding of your health risks, it is important to use BMI alongside other measurements like waist circumference and waist-to-height ratio, which are better indicators of abdominal fat and health risk.

If you are ready to take charge of your health, start by calculating your BMI, knowing what category you fall into, and then speak with your healthcare provider about what it means for you and what steps you can take to improve or maintain your health.

 

References:

1. Wandai ME, Aagaard-Hansen J, Manda SO, Norris SA. Transitions between body mass index categories, South Africa. Bull World Health Organ. 2020 Dec 1;98(12):878-885I. doi: 10.2471/BLT.20.255703. Available from here 

2. Chukwuonye II, Ohagwu KA, Ogah OS, John C, Oviasu E, Anyabolu EN, et al. Prevalence of overweight and obesity in Nigeria: Systematic review and meta-analysis of population-based studies. PLOS Glob Public Health. 2022 Jun 10;2(6):e0000515. doi: 10.1371/journal.pgph.0000515. Available from here

3. Muscogiuri G, Verde L, Colao A. Body mass index (Bmi): Still be used? European Journal of Internal Medicine. 2023 Nov;117:50–1. Available from here

4. Zierle-Ghosh A, Jan A. Physiology, body mass index. [Updated 2023 Nov. 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan -; [Cited 2025 Jun 7]. Available from here 

5. Weir CB, Jan A. Bmi classification percentile and cut off points. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan.- [Cited 2025 Jun 7]. Available from here

6. NIH. National Heart, Lung and Blood Institute. Calculate your bmi. [Internet, n.d]. [cited 2025 Jun 7]. Available from here 

7. Wu Y, Li D, Vermund SH. Advantages and limitations of the body mass index (Bmi) to assess adult obesity. Int J Environ Res Public Health. 2024 Jun 10;21(6):757. doi: 10.3390/ijerph21060757. Available from here 

8. Sweatt K, Garvey WT, Martins C. Strengths and limitations of bmi in the diagnosis of obesity: What is the path forward? Curr Obes Rep. 2024 Sep 1;13(3):584–95. doi: 10.1007/s13679-024-00580-1. Available from here 

9. Piqueras P, Ballester A, Durá-Gil JV, Martinez-Hervas S, Redón J, Real JT. Anthropometric indicators as a tool for diagnosis of obesity and other health risk factors: a literature review. Front Psychol. 2021 Jul 9;12. doi: 10.3389/fpsyg.2021.631179. Available from here 

 

Related: Rising Obesity Rates Among African Women: A Growing Public Health Concern

 

 

Published:  June 24, 2025

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