Why Obesity Happens: Understanding the Many Factors Behind Weight Gain

Dr. Aravinda J

Chairman and Chief Diabetologist
Dr Aravind's Diabetes Centre
Basaveshwara Nagar, Bengaluru.

Obesity is not caused by a single reason. It develops when several biological, psychological, and social factors interact over time. Understanding these influences can empower you to make healthier decisions and seek the right help when needed. Below is a simple explanation of how different factors contribute to weight gain.

1. Increased Food Intake: How Diet Can Lead to Obesity

What we eat and how much we eat play major roles in weight gain. But it’s not just about willpower—many underlying factors influence appetite and eating patterns.

Key influences include:

• Socio-cultural factors: Traditions, family habits, celebrations, and social pressure can encourage overeating.
• Lack of knowledge: Not knowing what foods are healthy or how many calories you actually need can lead to excess intake.
• Mental health conditions: Stress, anxiety, and depression can increase cravings, especially for high-calorie comfort foods.
• Increased hunger and reduced satiety: Some individuals naturally feel hungrier or less satisfied after meals due to hormonal or metabolic differences.
• Emotional eating: Using food as a coping mechanism for stress or sadness.
• Lack of sleep: Poor sleep disrupts hunger hormones, increasing appetite and cravings.
• Medications: Certain drugs (like steroids, antidepressants, or antipsychotics) can increase appetite.
• Socioeconomic status: Limited access to fresh food, busy work schedules, and affordability issues can push people toward unhealthy choices.

When these factors combine, they may lead to increased food intake, even when someone is trying to control their diet.

2. Reduced Energy Expenditure: How Your Body Burns Calories

Energy expenditure refers to how many calories your body uses daily. When this decreases, even regular eating can lead to weight gain.

Factors that reduce energy expenditure include:

• Age: Metabolism naturally slows as we age.
• Sex: Men and women burn calories differently due to hormones and muscle mass differences.
• Genetics and epigenetics: Your genes influence how fast your body burns calories.
• Neuroendocrine factors: Hormones like insulin, thyroid hormone, leptin, and cortisol strongly affect metabolism.
• Thermic effect of food: Some foods burn fewer calories during digestion.
• Brown fat levels: People with less brown fat burn fewer calories at rest.
• Body composition: More muscle means higher metabolism; more fat means lower metabolism.
• Medications: Some medicines slow down metabolism or cause fluid retention.

All these factors together can lead to reduced energy expenditure, making it easier to gain weight even without overeating.

3. Physical Inactivity: How Lifestyle Affects Obesity

Being physically inactive decreases the number of calories burned and weakens muscles over time. Modern lifestyles—desk jobs, long screen hours, and reduced outdoor activities—make this a widespread issue.

Physical inactivity is influenced by:

• Social determinants of health: Lack of safe spaces to exercise, long working hours, and limited access to facilities.
• Chronic medical conditions: Heart disease, arthritis, neuropathy, or breathing issues can limit mobility.
• Emotional barriers: Low motivation, fear of injury, or body-image concerns can discourage activity.
• Medications: Some drugs cause fatigue or muscle weakness.
• Low fitness level: When activity feels difficult, people tend to avoid it—creating a cycle of inactivity.

These influences can contribute to physical inactivity, which becomes a major driver of long-term weight gain.

Putting It All Together

Obesity develops through a combination of:

• Eating more calories than needed
• Burning fewer calories due to metabolism or health conditions
• Being less physically active due to lifestyle or medical issues

It is not a personal failure. It is a complex medical condition influenced by biology, environment, emotions, and societal factors.

What Patients Should Know

• Obesity is manageable with the right approach.
• A treatment plan should address diet, physical activity, medical factors, and emotional health.
• Consulting a healthcare provider—especially an endocrinologist or obesity specialist—helps identify the specific causes in your case.
• Even small, consistent changes can lead to meaningful improvements over time.

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