Obesity is defined as an abnormal or excessive accumulation of body fat posing a health risk, identified by a Body Mass Index (BMI) of 30 or higher. The global prevalence of obesity has steadily risen, becoming a major public health concern. From 1990 to 2022, the percentage of adults living with obesity more than doubled worldwide, reaching 16%.
Metabolic and Cardiovascular Diseases
Obesity contributes to metabolic and cardiovascular diseases.
Type 2 Diabetes
Insulin resistance, where cells do not respond effectively to insulin, leads to elevated blood glucose. Excess adipose tissue, particularly visceral fat, releases inflammatory molecules and free fatty acids that interfere with insulin signaling, exacerbating this resistance.
Hypertension
Hypertension is a frequent complication. Increased body mass requires the heart to work harder, raising arterial pressure. Obesity can also activate the renin-angiotensin-aldosterone system and lead to sodium retention, contributing to elevated blood pressure and vessel damage.
Heart Disease
Heart disease (coronary artery disease and heart failure) is linked to obesity. Coronary artery disease involves narrowing of heart arteries, often due to plaque buildup accelerated by chronic inflammation and abnormal lipid profiles. Heart failure can develop as the heart struggles to pump blood efficiently against increased resistance.
Stroke
Obesity elevates stroke risk, occurring when blood flow to the brain is interrupted. Hypertension, high cholesterol, and inflammation in individuals with obesity increase the likelihood of clot formation and vessel damage.
Non-Alcoholic Fatty Liver Disease (NAFLD)
NAFLD is prevalent, with excess fat accumulating in liver cells, driven by insulin resistance that promotes fat storage. If unmanaged, NAFLD can progress to non-alcoholic steatohepatitis (NASH), leading to inflammation, liver cell damage, and potentially cirrhosis or liver failure.
Cancers Linked to Obesity
Obesity increases the risk of several cancers through chronic inflammation, altered hormone levels, and increased growth factors. Adipose tissue produces pro-inflammatory cytokines that support cancer development.
Cancers like colorectal, breast (post-menopausal), endometrial, kidney, liver, and pancreatic cancers show a consistent link. In post-menopausal women, excess fat tissue converts androgen hormones into estrogen, stimulating hormone-sensitive cancer growth. Elevated insulin levels and insulin-like growth factors, common in obesity, promote cell proliferation and inhibit programmed cell death, contributing to cancer risk.
Chronic low-grade inflammation in obesity can damage DNA and support tumor growth. Liver inflammation in NAFLD can progress to liver cancer.
Musculoskeletal and Respiratory Conditions
Obesity leads to various musculoskeletal and respiratory conditions.
Osteoarthritis
Osteoarthritis, common in weight-bearing joints like the knees and hips, results from excess body weight. This directly increases mechanical stress on joint cartilage, leading to breakdown, pain, stiffness, and reduced mobility. Adipose tissue also releases inflammatory mediators that contribute to cartilage degradation.
Sleep Apnea
Excess fat deposits around the neck and throat can narrow the upper airway, leading to collapse during sleep. This obstruction leads to repeated pauses in breathing, disrupting sleep quality and reducing oxygen levels. Individuals with obesity may also experience reduced lung volume and impaired respiratory muscle function.
Asthma
Obesity can worsen asthma. Its increased inflammatory state can heighten airway inflammation and hyperresponsiveness, making symptoms more severe and difficult to control. Excess weight on the chest wall can also restrict lung expansion.
Other Significant Health Conditions
Obesity contributes to other health conditions.
Gallstones
Gallstones are more common in individuals with obesity due to changes in cholesterol and bile composition. Higher cholesterol saturation in bile and reduced gallbladder motility increase gallstone development.
Gout
Gout, a painful arthritis, is associated with obesity. Uric acid crystal accumulation in joints leads to severe pain and swelling. Obesity often correlates with increased uric acid production and reduced excretion, elevating blood uric acid levels.
Reproductive Health Issues
Reproductive health issues are a concern, particularly for women. Polycystic Ovary Syndrome (PCOS) is frequently observed in women with obesity. Obesity can exacerbate insulin resistance, a common feature of PCOS, disrupting hormone balance and leading to irregular periods, excess androgen production, and difficulty conceiving. Infertility in both men and women can also result from obesity due to hormonal imbalances and impaired reproductive function.