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Body mass index – BMI

BMI, formerly called the Quetelet index, is a measure for indicating nutritional status in adults. It is defined as a person’s weight in kilograms divided by the square of the person’s height in metres (kg/m2). For example, an adult who weighs 70 kg and whose height is 1.75 m will have a BMI of 22.9.

For adults over 20 years old, BMI falls into one of the following categories.

Table 1. Nutritional status


The BMI ranges are based on the effect excessive body fat has on disease and death and are reasonably well related to adiposity. BMI was developed as a risk indicator of disease; as BMI increases, so does the risk for some diseases. Some common conditions related to overweight and obesity include: premature death, cardiovascular diseases, high blood pressure, osteoarthritis, some cancers and diabetes.

BMI is also recommended for use in children and adolescents. In children, BMI is calculated as for adults and then compared with z-scores or percentiles. During childhood and adolescence the ratio between weight and height varies with sex and age, so the cut-off values that determine the nutritional status of those aged 0–19 years are gender- and age-specific. The cut-off points of the 2006 BMI-for-age reference for children aged 0–5 years for the diagnosis of overweight and obesity were set as the 97th and the 99th percentile, respectively. For those aged 5–19 years, overweight is defined as a BMI-for-age value over +1 SD and obesity as a BMI-for-age value over +2 SD.

Risks of Underweight

Being underweight carries several health risks, including a weakened immune system, increased susceptibility to infections, fatigue, and nutritional deficiencies. It can also lead to problems like anemia, osteoporosis, and difficulties with fertility, especially in women. 

Here’s a more detailed look at the disadvantages:

1. Weakened Immune System: Underweight individuals have a reduced ability to fight off infections due to lower white blood cell production, making them more prone to illness. This can lead to frequent colds, flu, and other infections, as well as slower recovery times. 

2. Nutritional Deficiencies: Underweight individuals may not be getting enough essential vitamins and minerals, leading to a range of health issues. This can include anemia (low red blood cell count), osteoporosis (weak bones), and other deficiencies affecting skin, hair, and overall well-being. 

3. Fatigue and Reduced Energy: Lack of sufficient calories can cause persistent fatigue and lethargy, making it difficult to perform daily tasks. This can also impact physical stamina and reduce the ability to work or participate in activities. 

4. Fertility Issues: In women, underweight conditions can disrupt the menstrual cycle, potentially leading to amenorrhea (absence of menstruation) and infertility. Underweight individuals may also experience difficulties conceiving and carrying a pregnancy to term. 

5. Bone Loss: Underweight individuals are at a higher risk of developing osteoporosis, a condition characterized by weakened and brittle bones. This can increase the risk of fractures and other bone-related problems later in life. 

6. Other Health Risks:

  • Increased Risk of Surgical Complications: Underweight individuals may be at a higher risk of complications during and after surgery. 
  • Heart Disease: Underweight individuals may have an increased risk of cardiovascular problems due to deficiencies in essential minerals like potassium, sodium, and calcium. 
  • Skin and Hair Problems: Lack of nutrients can lead to thinning skin, dry skin, and excessive hair loss. 
  • Mental Health Issues: In severe cases, being underweight and malnourished can contribute to depression and other mental health challenges. 

7. Mortality Risk: Studies have shown that underweight individuals may be at a higher risk of mortality, particularly in older adults. 

It’s important to note that while being underweight can have serious consequences, it’s not always a matter of choice. Medical conditions, eating disorders, and other factors can contribute to being underweight, and seeking professional help is crucial to address the underlying causes and improve health outcomes. 

Risks of Overweight/Obesity

Being overweight poses several health risks, including an increased chance of heart disease, type 2 diabetes, certain cancers, and joint problems like osteoarthritis. It can also lead to breathing difficulties like sleep apnea and affect mental health with increased rates of depression and anxiety. 

Here’s a more detailed breakdown of the disadvantages:

Physical Health Risks:

  • Cardiovascular Disease: Obesity increases the risk of heart disease, stroke, and high blood pressure. 
  • Type 2 Diabetes: Obesity is a major risk factor for developing type 2 diabetes, which can lead to various complications. 
  • Certain Cancers: Being overweight or obese is linked to an increased risk of several types of cancer, including breast, colorectal, and endometrial cancer. 
  • Joint Problems: Osteoarthritis and other musculoskeletal disorders are more common in obese individuals due to the stress on their joints. 
  • Breathing Problems: Sleep apnea and asthma are more prevalent in obese individuals, leading to breathing difficulties and sleep disruptions. 
  • Liver and Gallbladder Issues: Obesity can lead to fatty liver disease, non-alcoholic fatty liver disease, and gallstones. 
  • Kidney Disease: High blood pressure and diabetes, both associated with obesity, can contribute to kidney problems. 
  • Pregnancy Complications: Overweight or obese women during pregnancy may experience complications, including increased risk of gestational diabetes, high blood pressure, and other issues. 
  • Mental Health: Obesity is linked to a higher risk of depression, anxiety, and other mental health problems. 

Social and Psychological Impacts:

  • Social Stigma and Discrimination: People who are overweight or obese may face discrimination and negative stereotypes, leading to feelings of isolation, shame, and low self-esteem. 
  • Reduced Quality of Life: Obesity can impact quality of life, making it difficult to engage in physical activities and leading to fatigue and discomfort. 
  • Financial Burden: Obesity can lead to increased healthcare costs due to more frequent doctor visits, medications, and potential surgeries. 

It’s important to note that these risks can vary depending on the severity of obesity and individual factors. Early intervention and lifestyle changes can help mitigate many of these risks.

Benefits of regular physical activity

Regular physical activity – such as walking, cycling, or dancing – has significant benefits for health. For instance, it can reduce the risk of cardiovascular disease, diabetes and osteoporosis, help control weight, and promote mental well-being.

Taking part in physical activity increases opportunities for socialization, networking and cultural identity. Physical activity has a positive influence on the community and society by promoting social interaction and cohesion.

Regular physical activity may also benefit communities and economies through increased productivity in the workplace; lower worker absenteeism and turnover; and better performance in schools. In many countries a significant proportion of health spending is due to the costs of managing common noncommunicable diseases that are associated with inadequate physical activity. Promoting physical activity can be a highly cost-effective and sustainable public health intervention.

Active living benefits health at all ages. It is especially important to the healthy development of children and young people, and active ageing can make a dramatic difference to the well-being of older people.

Having the opportunity to enjoy quality recreation is vital to the health and personal development of all individuals, regardless of gender, functional ability, cultural background, age or socioeconomic status.

Benefits of a balanced diet

  • Opting for a balanced, adequate and varied diet is an important step towards a happy and healthy lifestyle.
  • Vitamins and minerals in the diet are vital to boost immunity and healthy development,
  • A healthy diet can protect the human body against certain types of diseases, in particular noncommunicable diseases such as obesity, diabetes, cardiovascular diseases, some types of cancer and skeletal conditions.
  • Healthy diets can also contribute to an adequate body weight.
  • Healthy eating is a good opportunity to enrich life by experimenting with different foods from different cultures, origins and with different ways to prepare food.
  • The benefits of eating a wide variety of foods are also emotional, as variety and colour are important ingredients of a balance diet.