What Is Obesity?


Have you ever wondered why obesity has become a worldwide epidemic? In a world marked by sedentary lifestyles and poor dietary choices, the answer lies in a perfect storm of modern-day factors that have contributed to this alarming global health crisis.

The World Health Organization (WHO) defines obesity as “abnormal or excessive fat accumulation that presents a health risk”. A body mass index (BMI) over 25 is considered overweight, and over 30 is obese. Fat itself is not a disease; however, the accumulation of extra fats can affect the functions of the organs, leading to adverse health effects.

The good news is that you can enhance your health and reduce health risks by losing some of your extra body fat. A small weight change can have a huge impact on your overall well-being. It's important to know that not all weight loss methods are effective for everyone. Most people have tried to lose weight multiple times, and keeping the weight off is just as important as losing it in the first place.

Types of obesity

The general population is classified into five categories according to their BMI.1 The BMI is a measure of body fat based on weight and height. To calculate the BMI, divide the weight in kilograms by the height in meters squared. 

CategoryBMI Range 
Normal weight18.5-24.9kg/m²
Class I-obesity-overweight25.0-29.9kg/m²
Class I-obesity-obesity30.0-39.9kg/m²
Class I-obesity-extreme obesity>40.0kg/m²

Causes of obesity

Obesity occurs when calorie intake is greater than calorie expenditure. Several factors contribute to obesity. These factors can be related to your genetic predisposition (probability of developing a disease due to the person's genetic make-up), eating habits, and lifestyle or built into the structure of your society, either on a local (family) or national level.

Genetic and environmental factors

Most individuals have some genetic predisposition to obesity, depending on their ethnicity and family history. However, genetic predisposition is unlikely to explain the rapid spread of obesity around the world.,2

The gene pool (collection of genes in a population) remains consistent over many generations. It takes a long time for a new mutation (genetic variation or change) to spread. Thus, the reason behind the rise in obesity rates over the past 40 years lies in the interaction between genetic and environmental factors. Our environment influences how much we eat and how active we are. Environmental changes that make it easier for individuals to overeat and harder to get enough physical activity have played a key role in triggering overweight and obesity.3

According to previous studies, physical activity reduces the effects of obesity-promoting FTO gene variant. People who carry the obesity-promoting FTO gene variant have a 23% higher risk of obesity than those without the gene variant. However, physical activity lowers the risk of obesity by 30% in active people than in inactive people who carry the gene.4

Junk food and high sugar diet consumption

The food industry is designed to sell products high in sugar and fat to leave you hungrier. These products include processed food, sweets, and sugary drinks, which have a lot of added calories and no nutritional value. The used ingredients promote addictive eating patterns, making you want to eat more. In some communities, these are the only available food options due to the cost and access.5

Sedentary lifestyle

A sedentary lifestyle is negatively associated with physical activity. Studies show that the longer you sit, the lazier and less motivated you become. Sitting increases your body's stiffness and contributes to aches and pains that discourage movement.67

Unfortunately, as social life, work, and shopping all continue to move online, an increase in sitting time and a decrease in physical activity is seen. In addition, most industries are moving toward automation, computers, and remote work; thus, employees are now spending longer hours at desks rather than on their feet.

Hormonal imbalance

Hormones regulate your hunger and satiety (satisfaction) signals. They can affect your appetite and make you crave more food even when you don’t need more calories. Several factors can disrupt the hormonal regulatory process, such as high cortisol levels in men and decreased estradiol (a specific estrogen hormone) in women. In addition, certain conditions can contribute to hormonal weight gain including:

Psychological factors

Loneliness, chronic stress, depression, anxiety, and mental health conditions such as bipolar disorder may lead you to use food as a way to cope. These factors lead the individual to make poor food choices by eating certain types of foods that activate your brain's pleasure centre, foods that tend to be higher in calories.7


Certain medications are associated with significant weight gain. These medications include some types of steroids, antidepressants, diabetes medications, hypertension medications, and antipsychotics (drugs used to treat psychosis).8

Signs and symptoms of obesity

  • Excess weight or body fat, particularly around the waist
  • Difficulty in doing physical activity
  • Fatigue
  • Shortness of breath
  • Excessive sweating
  • Trouble sleeping
  • Snoring
  • Skin problems like increased skin folds
  • Back and joint pain
  • Psychological issues include depression, negative self-esteem, and social isolation9

Management and treatment for obesity

Dietary modifications

Reducing calorie intake and controlling portion sizes help maintain a healthy weight. Try to add more vegetables, fruits, whole grains, and protein (fish, poultry, beans) to your diet and cut off sugared beverages, processed fast food, candies, and sweets.10

Regular physical activity

Physical activity increases your total energy expenditure, which helps to maintain your weight or even lose weight. Incorporating aerobic exercises (such as walking, running, or swimming) and strength training can help you burn calories, increase metabolism, and improve overall fitness.11

Behavioural therapy

This approach aims to identify and modify unhealthy behaviours and habits related to eating, physical activity, as well as emotional and psychological factors. It often involves setting realistic goals, self-monitoring progress, developing coping strategies, and seeking support from healthcare professionals or support groups and methods such as cognitive behavioural therapy.12


Medications can be prescribed to assist with weight loss and management. These medications work in different ways. For example, some medications help you feel less hungry (appetite suppressants), while others prevent fat in the foods eaten from being absorbed in the intestines. These medications are typically used in conjunction with lifestyle changes and are prescribed under the guidance of a healthcare professional.


Bariatric surgery is a term used to describe several weight loss surgeries that involve a surgical reduction of the size of the stomach or surgical re-routing of the patient's small intestine to reduce the ability of the stomach to take in food. Bariatric surgery is performed when diet and exercise are not effective or when you have serious health problems because of your weight.


Obesity diagnosis involves measuring your weight, height, BMI, and waist circumference. The doctor will ask about your history of medical conditions, medications, changes in weight, sleeping and exercise patterns, and stress factors.

The doctor will also examine your vital functions by taking your blood pressure and heart rate. In addition, a blood test will be conducted to evaluate your blood glucose, cholesterol levels and hormone levels. All the collected information will be used to diagnose your obesity and propose a proper treatment for your case.

Risk factors

Although obesity can affect anyone, certain factors increase the risk of developing the condition. These factors include:

  • Family history of obesity
  • Unhealthy diet
  • A sedentary lifestyle and lack of physical activity
  • Psychological factors such as stress, lack of sleep, anxiety, and depression
  • Health conditions
  • Certain medications


Obesity is not just a matter of appearance or body weight; it contributes to several serious health complications, including:

  • Type 2 diabetes, which is linked to obesity in 50% of cases
  • High blood pressure, high cholesterol, and heart diseases like stroke and heart attack14
  • Respiratory problems, such as obese asthma (a type of asthma found in obese people), shortness of breath, and sleep apnea (breathing difficulties during sleep)
  • Joint problems and osteoarthritis
  • Gastro-oesophageal reflux disease (GORD, retrograde flow of stomach contents back into the oesophagus), heartburn, and hiatal hernia (occurs when the upper part of the stomach pushes through an opening in the diaphragm and into the chest cavity)


How can I prevent obesity?

You can follow these tips to reduce the risk of developing obesity.

  1. Maintain a healthy and balanced diet that includes vegetables, fruits, meats, nuts, and whole grains
  2. Reduce the consumption of fast food, sweets, and sugary drinks
  3. Increase physical activity
  4. Decrease sit time, which includes television time, screen time, and others
  5. Get enough sleep. Aim for 7-9 hours of quality sleep each night
  6. Reduce stress

How common is obesity?

According to the WHO, worldwide obesity has tripled since 1975. In 2016, more than 1.9 billion (39%) adults who are older than 18 years were overweight, and 650 million (13%) were obese. Over 340 million children and adolescents, aged between five and 19 years, were overweight or obese. In 2020, 39 million children who are under the age of five were overweight or obese.

When should I see a doctor?

You should consult a doctor if you have been gaining weight and when your attempt to lose weight by maintaining a healthy diet and exercising is unsuccessful. Under normal conditions, following a healthy diet and exercising are usually enough to start losing your excess weight.


Obesity is a complex condition characterised by excessive body fat accumulation, which can have a significant impact on an individual's overall health and quality of life. It is influenced by a combination of genetic, environmental, and lifestyle factors. The management and treatment of obesity involve lifestyle modifications, dietary changes, physical activity, behavioural therapy, and in some cases, medical interventions or surgery. Prevention through healthy habits is crucial, considering the global rise in obesity rates. Consulting with a healthcare professional is recommended for proper diagnosis and guidance.


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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Mayasah Al-Nema

PhD Pharmaceutical Sciences – MSc Pharmaceutical Chemistry – BSc Pharmacy, UCSI University, Malaysia

Mayasah is a skilled and experienced scientific researcher and writer with over seven years of experience in writing scientific articles and books. In addition to her expertise in research, she has three years of experience as a teaching assistant at UCSI University, providing her with valuable insights into effective teaching practices. Mayasah has participated in numerous international conferences, where she has presented her research findings to peers and colleagues. She is also a respected peer-reviewer for three prominent scientific journals, providing expert analysis and feedback on articles submitted for publication.

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