Overweight and obesity are significant global health concerns, affecting populations worldwide. Their expanding reach and associated health implications are drawing increasing attention. Understanding the scale and nature of this phenomenon is important for public health efforts. Once primarily a concern in high-income nations, excess weight is now a challenge faced by countries at all economic levels. This evolving landscape highlights the need to understand how these conditions are defined, their global footprint, and contributing factors.
Defining Overweight and Obesity
Overweight and obesity are medically categorized based on an individual’s Body Mass Index (BMI), a widely used screening tool calculated from weight in kilograms divided by the square of height in meters. For adults, the World Health Organization (WHO) defines overweight as a BMI of 25 or greater, and obesity as a BMI of 30 or greater. Obesity is further classified into Class I (30-34.9 kg/m²), Class II (35-39.9 kg/m²), and Class III (40 kg/m² or greater). While BMI is a standard for population-level assessment, it has limitations, such as not distinguishing between muscle and fat mass or accounting for ethnic variations.
For children and adolescents aged 5-19 years, overweight is defined as BMI-for-age greater than one standard deviation above the WHO Growth Reference median, and obesity is more than two standard deviations above this median. For children under five years, overweight is weight-for-height greater than two standard deviations above the WHO Child Growth Standards median, with obesity being three standard deviations above the median. These definitions provide a consistent framework for tracking global trends in body weight.
Global Prevalence: The Current Picture
The global prevalence of overweight and obesity is substantial. In 2022, approximately 2.5 billion adults aged 18 years and older were overweight, representing 43% of the adult population. Of these, 890 million adults were living with obesity globally. This means that in 2022, about one in eight people worldwide were living with obesity.
The issue also extends to younger populations. In 2022, over 390 million children and adolescents aged 5-19 years were overweight, including 160 million who were living with obesity. An estimated 35 million children under the age of five were overweight in 2024. These figures highlight that a substantial portion of the global population across all age groups is currently living with excess weight.
Shifting Global Landscape
The prevalence of overweight and obesity has shown a significant increase over recent decades. Worldwide adult obesity more than doubled between 1990 and 2022, while adolescent obesity quadrupled during the same period. The prevalence of overweight and obesity among children and adolescents aged 5-19 years surged from 8% in 1990 to 20% in 2022. This rapid rise indicates a significant shift in global health patterns.
Historically considered a problem primarily in high-income countries, overweight and obesity are now rapidly increasing in low- and middle-income countries (LMICs). Many LMICs face a “double burden of malnutrition,” grappling with undernutrition alongside a rapid increase in overweight and obesity. Projections suggest this trend will continue, with the total number of adults with overweight and obesity forecasted to rise to 3.8 billion by 2050, comprising nearly 60% of adults worldwide.
Contributing Factors
Several interconnected factors contribute to the global rise in overweight and obesity. Changes in dietary patterns play a significant role, marked by increased consumption of energy-dense foods that are high in fat, sugar, and salt, often characteristic of ultra-processed foods. These dietary shifts often coincide with reduced physical activity levels, as urbanization, technological advancements, and evolving work and leisure habits lead to more sedentary lifestyles.
Socioeconomic and environmental factors also influence these trends. Poverty can paradoxically contribute to higher rates of overweight and obesity, as cheaper, less nutritious foods become more accessible. The pervasive marketing of unhealthy foods and insufficient access to affordable, healthy food options or safe spaces for physical activity further exacerbate the problem. While genetic and biological predispositions can influence an individual’s weight, environmental factors are largely driving the observed population-level increases.