What is Obesity Basics?

An overview of obesity: what it is, why it matters, and how it affects health.

Heart & Circulation

Obesity Basics

2025-09-09

Intro

Obesity is a chronic condition where excess body fat increases the risk of disease. It’s commonly assessed using Body Mass Index (BMI), waist circumference, and waist-to-hip ratio. Beyond weight, obesity influences metabolism, inflammation, and cardiovascular risk.

Key Points

Defined by excess body fat, not just body weight.
Commonly measured using BMI (≥30 in adults) but waist circumference and WHR are better predictors of health risks.
Strongly linked to diabetes, heart disease, stroke, and certain cancers.
Management focuses on lifestyle changes, medications, and in some cases surgery.

Background

Global obesity rates have tripled since 1975. The condition is driven by an interplay of genetics, environment, diet, physical activity, and socioeconomic factors. Obesity is more than appearance — it’s a major driver of chronic disease worldwide.

Causes or Mechanisms

Energy imbalance: calories consumed vs. calories burned.
Hormonal regulation: insulin, leptin, and gut hormones affect appetite and fat storage.
Environment: availability of calorie-dense food, sedentary lifestyles.
Genetics and epigenetics: predispositions influence metabolism and fat storage.

Diagnosis / Options

BMI: ≥25 = overweight, ≥30 = obese.
Waist circumference / WHR: stronger predictors of cardiovascular risk.
Treatment: nutrition and exercise, behavioral therapy, medications (e.g. GLP-1 agonists), bariatric surgery.

Risks / Prognosis

Increased risk of heart disease, type 2 diabetes, certain cancers, osteoarthritis, and reduced life expectancy.
Prognosis improves with modest weight loss (5–10%), reduced waist circumference, and healthier fat distribution.

FAQ

Q: Can you be obese but healthy?
A: Some people with obesity have normal blood pressure, glucose, and cholesterol. However, the risk of chronic disease is still higher than in those without obesity.

Q: Is BMI enough?
A: No. Waist circumference and waist-to-hip ratio provide additional insight into risk.