Understanding Obesity: A Global Health Challenge

Key Facts

• In 2022, 1 in 8 people in the world were living with obesity.
• Worldwide adult obesity has more than doubled since 1990, and adolescent obesity has quadrupled.
• In 2022, 2.5 billion adults (18 years and older) were overweight. Of these, 890 million were living with obesity.
• In 2022, 43% of adults aged 18 years and over were overweight, and 16% were living with obesity.
• By 2024, an estimated 35 million children under the age of 5 will be overweight.
• Over 390 million children and adolescents aged 5–19 years were overweight in 2022, including 160 million living with obesity.

Overview

Overweight and obesity are increasingly recognized as significant global health issues. Defined as conditions characterized by excessive fat deposits, they are more than just aesthetic concerns; they are chronic diseases influenced by various factors including genetics, eating behaviors, environmental conditions, and societal norms.

The World Health Organization (WHO) classifies obesity as a relapsing disease that arises from complex interactions between these factors. With greater food security and socioeconomic development worldwide, lifestyle changes and shifts in diet—accelerated by globalization—have contributed to the rise of obesity as a public health crisis, with over 1 billion individuals affected globally.

Obesity is typically diagnosed through Body Mass Index (BMI) calculations, which measure weight in relation to height. For adults, a BMI of 25 or greater is considered overweight, while a BMI of 30 or more is classified as obesity. However, for children and adolescents, different growth charts are employed to evaluate their weight status due to differences in growth patterns.

Definition of Overweight and Obesity

Adults

For adults:

• Overweight: BMI ≥ 25
• Obesity: BMI ≥ 30

Children

For children, classifications depend on their age:

Children Aged 5–19 Years

• Overweight: BMI-for-age greater than 1 standard deviation above the WHO Growth Reference median.
• Obesity: BMI-for-age greater than 2 standard deviations above the WHO Growth Reference median.

Children Under 5 Years

• Overweight: Weight-for-height greater than 2 standard deviations above the WHO Child Growth Standards median.
• Obesity: Weight-for-height greater than 3 standard deviations above the WHO Child Growth Standards median.

Prevalence of Overweight and Obesity

As of 2022, an estimated 2.5 billion adults aged 18 years and older were overweight, with approximately 890 million classified as obese. This indicates that around 43% of adults were overweight—a significant rise from 1990, when only 25% were classified as such. The incidence of overweight varies by region, with 31% in the WHO South-East Asia Region compared to 67% in the Region of the Americas.

The prevalence of obesity has similarly risen dramatically, more than doubling from 1990 to 2022. Childhood obesity is particularly alarming; in 2024, it’s projected that 35 million children under 5 will be overweight. The epidemic is no longer isolated to high-income nations, with many low- and middle-income countries witnessing rapid increases in obesity rates across all socioeconomic groups.

In 2022 alone, over 390 million children and adolescents aged 5–19 were overweight. This prevalence has risen sharply from just 8% in 1990 to 20% in 2022, with troubling implications for the health of future generations.

Causes of Overweight and Obesity

The rising rates of overweight and obesity are largely attributed to an imbalance between calorie consumption and physical activity. However, these conditions also emerge from a nexus of environmental, socio-cultural, and genetic factors.

Key environmental determinants include:

• Limited access to affordable, healthy foods
• The prevalence of unhealthy foods high in fats, sugars, and salt
• Insufficient opportunities for physical activity

These factors contribute to unhealthy dietary patterns and sedentary lifestyles, further increasing the risks of obesity. Health systems often lack the mechanisms to identify and address weight issues early, exacerbating the situation.

Common Health Consequences

Overweight and obesity take a toll on individual health and present broader societal challenges. They are linked to numerous noncommunicable diseases (NCDs), including cardiovascular diseases, diabetes, and certain types of cancer. In 2021, it was estimated that diseases related to excess body weight caused around 3.7 million deaths globally.

Childhood obesity is particularly concerning as it predisposes children to significant health issues later in life, including type 2 diabetes and cardiovascular problems. Psychosocial consequences, including stigma and bullying, further complicate the lives of affected youth.

Economically, the impact of the obesity epidemic is staggering, with potential costs projected to reach US$3 trillion by 2030 and more than US$18 trillion by 2060. This growing burden affects not just individuals but also healthcare systems and national economies, particularly in low- and middle-income countries.

Facing a Double Burden of Malnutrition

Countries grappling with obesity often face a dual challenge: while they combat infectious diseases and undernutrition, they simultaneously witness the rise of obesity. This duality is often found within the same community or household, with children facing both undernutrition and the consumption of energy-dense, nutrient-poor foods.

In low- and middle-income regions, children are frequently exposed to high-fat, high-sugar diets alongside inadequate nutrition, creating a cycle that exacerbates health risks.

Prevention and Management

The good news is that overweight and obesity are largely preventable and manageable. Individuals can adopt measures throughout their life stages to mitigate their risks, starting even before conception:

• Manage weight gain during pregnancy
• Practice exclusive breastfeeding for the first six months
• Encourage healthy eating and regular physical activity in children
• Limit screen time and intake of sugary beverages

From a healthcare perspective, practitioners must assess weight and height regularly, offer lifestyle counseling, and monitor comorbidities linked to obesity.

Addressing obesity is not solely an individual responsibility. Effective public health strategies must include structural changes within communities to promote healthy food environments and physical activity.

Multisectoral policies are crucial to shift dietary patterns and physical activity levels at community, national, and global levels. This involves incorporating health considerations into urban planning, food policy, and education systems.

WHO Response

Recognizing the urgency of the obesity crisis, WHO has initiated several strategies over the years. The World Health Assembly has set Global Nutrition Targets to combat childhood overweight and halt the rise of diabetes and obesity by 2030. Recent recommendations have emphasized comprehensive approaches to obesity management, recognizing it as a complex, lifelong condition requiring multifaceted responses.

The future of obesity prevention and treatment will depend on collaborative efforts from governments, healthcare systems, industry stakeholders, and communities. Only through comprehensive action can we hope to address this global health challenge effectively.