Decoding Obesity: Causes Beyond Calories

For years, obesity has been explained in a simple way: “Eat less, move more.” While eating habits and physical activity matter, this explanation ignores a much bigger truth. Obesity is not just about calories, it is a complex medical condition influenced by the brain, hormones, genetics, emotions, and the environment we live in.

Obesity Today

Obesity is rising at an alarming pace across the globe. According to the World Obesity Federation’s 2025 Atlas, the number of adults living with obesity is projected to more than double between 2010 and 2030, increasing from 524 million to 1.13 billion people.1 Once thought to be a problem only in wealthier countries, obesity is now growing rapidly in low- and middle-income nations, including India.

What’s even more concerning is that this trend is no longer limited to adults. As per UNICEF’s Child Nutrition Global Report 2025, obesity has now overtaken underweight as the most common form of malnutrition among school-aged children and adolescents worldwide.² Fig 1: Depicts the surge in overweight and obesity in India; under-five children increased from 1.5% to 3.4% (+127%), adolescent girls from 2.4% to 5.4% (+125%), and adolescent boys from 1.7% to 6.6% (+288%); in adults, obesity rose by 91% in women (12.6% to 24.0%) and 146% in men (9.3% to 22.9%) between NFHS-3 (2005–06) and NFHS-5 (2019–21).

Understanding Obesity 

Obesity is a chronic health condition characterized by excessive body fat accumulation that poses a risk to overall health. Even a small amount of extra weight can increase the risk of health problems. The more weight you gain, the higher the risk becomes.

Excess weight can strain bones and joints, leading to musculoskeletal problems. It also raises the likelihood of type 2 diabetes, heart disease, and stroke, the leading causes of death worldwide.

Knowing whether you are overweight or obese is the first step toward taking control of your health. However, there’s no one single number that defines obesity. Doctors use multiple measurements to evaluate body fat levels and identify health risks early. These include:

Obesity: A Disease, Not a Choice

Research over the last 30 years shows that weight gain is not just a personal choice rather is affected by:

·         Biology (body and genes)

·         Psychology (stress, emotions, sleep)

·         Environment (easy access to junk food, lack of physical activity, screen time) 

Genetics and Obesity: When Your DNA Plays a Role

For many people, genetics plays a major role in how their body store fat, how hungry they feel, and how easily they gain weight. Some people have genes that make them gain weight more easily, especially if they eat sugary, high-calorie foods. 

Research has identified 200–500 genes associated with obesity.3 Moreover, measurements such as Body Mass Index (BMI), waist-to-hip ratio, and skinfold thickness often show patterns that run in families. A study on identical twins reveals that their body weight tends to remain similar even when they grow up in different environments. 

Impact of Hormones on Body Weight

The hormones of your body also influence your weight. Leptin and ghrelin are two key hormones that help control your appetite. 

• Ghrelin is often called the “hunger hormone” because it signals your brain when your stomach is empty and it’s time to eat. 
• Leptin, on the other hand, is known as the “fullness hormone.” It is released by fat cells and tells the brain that the body has enough energy stored, helping to reduce hunger. 

In a healthy balance, ghrelin rises before meals and drops after you eat, while leptin increases to signal fullness. However, in obesity, this balance gets disrupted. The body may produce a lot of leptin, but the brain stops responding to it, a condition called leptin resistance. As a result, the person still feels hungry even though their body has enough fat stored. 

Fig 3: Shows the role and impact of hormones on hunger and appetite

Other hormones like thyroid hormones which affect metabolism and gut hormones like GLP-1 also influence appetite, cravings, and fat storage. When these hormones are out of balance, they can make weight gain easier and weight loss harder.

The Sleep–Obesity Connection

Sleep plays a major role in how your body handles sugar, hunger, and metabolism. When you don’t get enough sleep:

• Your body becomes less sensitive to insulin, making sugar control harder.
• Levels of leptin (the fullness hormone) drop, so you don’t feel satisfied after eating.
• Levels of ghrelin (the hunger hormone) and cortisol (stress hormone) increase, causing more cravings—especially for junk food.

Poor sleep also leads to lower energy, which makes you less likely to exercise. Research has shown that even a change in average sleep duration can influence obesity risk in people who have certain genetic tendencies.

Emotional Eating: When Stress Shapes Your Appetite

Chronic stress doesn’t just affect the mind—it affects the body. When you are under long-term stress, your body produces more cortisol, a hormone that:

• Increases appetite
• Triggers cravings for sugary and salty foods
• Encourages fat storage, especially around the abdomen

Stress can also lead to emotional or comfort eating, making weight control harder. Studies show that people experiencing multiple stressors are more likely to gain weight, especially when they have a genetic tendency toward obesity.

Medical Conditions That Influence Weight

Medical conditions such as hypothyroidism (an underactive thyroid) and Cushing's syndrome (which involves excess cortisol) can lead to weight gain. Other contributing factors include Polycystic Ovary Syndrome (PCOS), diabetes, and various neurological and genetic disorders. Additionally, metabolic syndrome and conditions like heart, kidney, or liver problems, which can cause fluid retention in the body, may also increase overall weight.

Approaches to Managing Obesity

Obesity management involves a comprehensive approach that includes lifestyle changes like diet and exercise, as well as potentially medication or surgery depending on the individual's health.

Fig 4: Tabulates various strategies and tips for effective obesity management

When to seek Medical Help?

If you’re worried about your weight or experiencing health issues related to it, don’t hesitate to talk to your doctor. They can assess your health, evaluate your risks and create a personalized weight-management plan.

Conclusion 

Obesity Is Manageable — With Understanding, Support, and Action

Recognizing obesity as a disease helps shift the conversation from “try harder” to “let’s treat it properly.” With the right and guided support, people can lose weight effectively and improve their overall health.

References:

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