Obesity and Public Health: An Epidemiological Perspective on a Global Epidemic

Obesity has emerged as one of the most urgent and complex public health challenges of the 21^st century, with profound implications for health systems, economic stability, and social equity. According to the World Health Organization (WHO), the global prevalence of obesity has nearly tripled since 1975, and in 2023, over 1 billion people were living with obesity, including 650 million adults, 340 million adolescents, and 39 million children [1]. This escalating trend has been described as a global epidemic, affecting populations across age groups, geographies, and income levels.

Once considered a problem limited to high-income countries, obesity is now rapidly rising in low- and middle-income countries (LMICs). This is driven by urbanization, economic development, and shifts in dietary patterns toward ultra-processed, high-fat, high-sugar foods, combined with declining physical activity levels [2]. For example, between 2000 and 2016, the prevalence of obesity in Africa nearly doubled, with countries such as Egypt and South Africa experiencing some of the highest rates on the continent [3]. In Asia, nations like India and China are witnessing a surge in obesity-related non-communicable diseases (NCDs), including type 2 diabetes, cardiovascular disease, and certain cancers, placing additional stress on already overburdened health systems [4,5].

Obesity is defined by an abnormal or excessive fat accumulation that presents a risk to health, typically measured using body mass index (BMI). A BMI of 30 or more is classified as obese, although BMI does not account for fat distribution or muscle mass, leading some researchers to advocate for complementary measures such as waist-to-hip ratio or body fat percentage [6]. As a multifactorial epidemiological issue, obesity results from the interplay of biological predisposition, individual behaviors, socio-economic status, environmental factors, and policy contexts. The nutrition transition in many LMICs—marked by a move from traditional diets to Westernized food systems—is a significant driver of rising obesity rates [7].

Moreover, obesity underscores the double burden of malnutrition in many parts of the world, particularly in LMICs. In countries such as India, Indonesia, and Nigeria, undernutrition and micronutrient deficiencies coexist with increasing rates of overweight and obesity, sometimes within the same households or communities [8-10]. This paradox reflects the inequities embedded in global food systems and access to health-promoting environments.

This review aims to provide a comprehensive, evidencebased overview of the obesity epidemic from an epidemiological perspective, addressing global trends, determinants, associated health risks, and the effectiveness of public health interventions. It also seeks to highlight the need for multisectoral, equity-focused responses to prevent and manage obesity across diverse socioeconomic and geographic contexts.

Globally, obesity has reached unprecedented levels, with profound implications for public health. According to the World Health Organization (WHO), as of 2022, 16% of the world’s adult population were obese, and 43% were overweight (43% of men and 44% of women) [11]. These figures reflect a tripling of global obesity rates since 1975. The Global Burden of Disease (GBD) Study 2019 ranks high body mass index (BMI) as the fourth leading risk factor for global mortality, linked to over 5 million deaths annually and responsible for significant years of life lost and lived with disability [12].

One of the most alarming trends is the sharp rise in childhood obesity. Globally, the prevalence of overweight and obesity among children and adolescents aged 5–19 years surged from just 4% in 1975 to 20% in 2022 - a five-fold increase [13]. A systemic review indicates nine of the ten Pacific Island nations, had highest prevalence of obesity, highlighting a growing crisis [14].

While countries like the United States report the highest obesity prevalence among adults (30.5% in 1999 -42.4% in 2018), low- and middle-income countries (LMICs) are experiencing rapid increases, particularly in urban centers [15]. This global spread is strongly associated with economic transitions, rapid urbanization, and the globalization of processed food systems. For instance, in Mexico and Brazil, traditional diets are increasingly replaced by energydense, nutrient-poor foods, leading to the coexistence of obesity with undernutrition and micronutrient deficiencies [16].

The primary modifiable determinants of obesity include poor dietary habits and physical inactivity. Global dietary patterns have shifted toward higher intake of ultra-processed foods, sugarsweetened beverages (SSBs), and saturated fats, contributing to excess caloric consumption [17]. Meanwhile, physical activity levels have declined, particularly in urban environments, due to increased reliance on motorized transport, sedentary jobs, and screen-based recreation. The Lancet Physical Activity Series (2016) warned that over 1.4 billion adults globally are insufficiently active, with the highest rates in high-income countries [18].

Social determinants of health—including education, income, gender, and neighborhood environment—play a significant role in shaping obesity risk [19]. In high-income countries, lower-income and marginalized populations are disproportionately affected due to limited access to healthy food, recreational spaces, and healthcare services. Conversely, in many LMICs, obesity initially emerges among the more affluent due to greater access to caloriedense foods and sedentary lifestyles, but eventually becomes more prevalent among the urban and rural poor, especially women [7].

Although genetics can influence individual susceptibility to obesity, the rapid rise in prevalence globally cannot be explained by genetics alone. The concept of the “obesogenic environment “as in figure below- which includes the built environment, food systems, and marketing practices - has gained prominence in public health discourse [20]. Aggressive marketing of unhealthy food and beverages, especially toward children and adolescents, plays a pivotal role. A meta-analysis has confirmed that exposure to food advertising significantly increases children’s intake of high-calorie, low-nutrient foods [21].

The Obesogenic Environment

Obesity is associated with a wide range of comorbidities, contributing significantly to the global burden NCDs, higher BMI leads to 3.7 million deaths by NCDs and a strong linkage to type 2 diabetes [22]. Oflate obesity has been associated with depression, anxiety, and low self-esteem, particularly in adolescents [23].

Furthermore, obesity deepens health inequalities and has measurable effects on longevity. According to the OECD (2020), obesity reduces life expectancy by 2 to 4 years on average and accounts for 3.3% of total healthcare expenditure across member states [24]. In the United States, the economic burden of obesity was estimated at $173 billion in 2019 due to rising obesity-related healthcare costs and lost productivity [25]. LMICs also face growing indirect costs, which further strain under-resourced health systems.

Governments have increasingly turned to regulatory and fiscal measures to reshape food environments and promote healthier behaviors:
a. Sugar-sweetened beverage (SSB) taxes in Mexico, Chile, South Africa, and the UK have led to reductions in purchase and consumption [26].
b. Front-of-package nutrition labeling (e.g., Chile’s black warning labels) empowers consumers to make informed choices and has influenced product reformulation [27].
c. Restrictions on junk food advertising targeting children, and school food policies, are gaining momentum in regions like the EU and Latin America [28].
d. Urban design initiatives (e.g., bike lanes, green spaces, pedestrian zones) promote physical activity and reduce car dependency [29].

Initiatives like the UN Decade of Action on Nutrition (2016– 2025) and the WHO Global Action Plan on NCDs (2013–2020) emphasize the need for multisector collaboration—integrating efforts across agriculture, education, urban planning, finance, and trade [30,31]. Global frameworks encourage countries to set national obesity targets, implement monitoring systems, and address conflicts of interest, especially from the food and beverage industry. Yet, progress is uneven. Many countries still lack coherent national strategies or face political and commercial resistance to implementing evidence-based interventions. Without systemic reforms and stronger accountability mechanisms, the global obesity epidemic will continue to expand, exacerbating NCD burdens and widening health disparities.

Obesity is widely recognized as a global epidemic fueled by a complex web of interrelated determinants spanning biological, behavioral, environmental, social, and commercial domains. This global surge poses profound challenges to health systems worldwide, straining resources through increased demands for chronic disease management, and imposing heavy economic burdens through rising healthcare costs and lost productivity. Furthermore, obesity exacerbates social inequities, disproportionately affecting vulnerable populations and amplifying disparities in health outcomes and access to care. Effective public health strategies must therefore be comprehensive and context-specific, integrating policy regulation (e.g., taxation of sugar-sweetened beverages, restrictions on junk food marketing, mandatory front-of-package labeling) with community engagement to ensure culturally appropriate and equitable implementation. For example, countries like Chile and Mexico have demonstrated the effectiveness of regulatory policies combined with public education campaigns in reducing consumption of unhealthy foods and beverages [28].

Moreover, reversing the obesity epidemic requires strong political will, underpinned by robust surveillance and monitoring systems that track prevalence trends, risk factors, and intervention outcomes. Accountability mechanisms are essential to hold governments and corporations responsible for their roles in perpetuating obesogenic environments. Thus, tackling obesity demands a multisector approach that transcends traditional healthcare models and individual behavior change. It requires sustained commitment at local, national, and international levels to create environments that promote health equity, empower healthier choices, and ultimately stem the tide of this complex and multifaceted epidemic.

None.

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