Malnutrition, encompassing deficiencies, excesses, or imbalances in nutrient intake, presents a significant global health challenge. It manifests in various forms, including undernutrition (wasting, stunting, underweight), micronutrient-related malnutrition (deficiencies or excesses), and overweight, obesity, and diet-related noncommunicable diseases. Recognizing the severity and widespread nature of malnutrition is crucial for developing effective strategies to combat it.
Understanding the Different Facets of Malnutrition
Malnutrition is not simply about being underweight; it's a multifaceted issue with far-reaching consequences. The World Health Organization (WHO) recognizes three broad groups of conditions under the umbrella of malnutrition:
- Undernutrition: This category includes wasting, stunting, underweight, and micronutrient deficiencies.
- Micronutrient-related malnutrition: This involves deficiencies or excesses of essential vitamins and minerals.
- Overweight, obesity, and diet-related noncommunicable diseases: This encompasses conditions like heart disease, stroke, diabetes, and certain cancers linked to unhealthy diets.
Undernutrition: A Closer Look
Undernutrition weakens the body's defenses, making individuals, especially children, more susceptible to illness and death. There are four sub-forms of undernutrition:
- Wasting: Defined as low weight-for-height, it often indicates recent and severe weight loss due to insufficient food intake or infectious diseases like diarrhea. According to the World Health Organization… Wasting, or being too thin for one’s age, is defined as a weight-for-height that is more than two standard deviations below the World Health Organization.
- Stunting: Characterized by low height-for-age, stunting reflects chronic or recurrent undernutrition linked to poor socioeconomic conditions, inadequate maternal health and nutrition, frequent illness, and improper infant and young child feeding practices. Stunting, or being too short for one’s age, is defined as a height that is more than two standard deviations below the World Health Organization.
- Underweight: Children with low weight-for-age are classified as underweight and may experience stunting, wasting, or both.
- Micronutrient Deficiencies: Inadequacies in vitamin and mineral intake can hinder the body's ability to produce essential enzymes, hormones, and other substances vital for growth and development.
The Growing Problem of Overweight and Obesity
Overweight and obesity occur when a person's weight is too high for their height, leading to abnormal or excessive fat accumulation that can impair health. Body mass index (BMI), calculated as weight in kilograms divided by the square of height in meters (kg/m²), is a common tool for classifying overweight and obesity. In adults, a BMI of 25 or more indicates overweight, while a BMI of 30 or more signifies obesity. It's important to note that BMI thresholds for children and adolescents vary by age.
The rise in overweight and obesity is driven by an imbalance between energy consumed (too much) and energy expended (too little). Globally, people are consuming more energy-dense foods and drinks, which are high in sugars and fats, and engaging in less physical activity.
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Diet-Related Noncommunicable Diseases
Unhealthy diets and poor nutrition are major risk factors for diet-related noncommunicable diseases (NCDs) such as cardiovascular diseases, certain cancers, and diabetes. These diseases pose a significant threat to global health.
The Scope of Malnutrition: A Global Perspective
Malnutrition affects every country in the world, with women, infants, children, and adolescents being particularly vulnerable. Poverty exacerbates the risk of malnutrition, creating a vicious cycle of ill-health and economic hardship.
The statistics paint a concerning picture:
- In 2022, approximately 390 million adults worldwide were underweight, while 2.5 billion were overweight, including 890 million with obesity.
- Among children and adolescents aged 5-19 years, 390 million were overweight, including 160 million with obesity, and 190 million were living with thinness.
- An estimated 149 million children under 5 years of age were stunted, and 37 million were overweight or obese in 2022.
- Nearly half of deaths among children under 5 years of age are linked to undernutrition, primarily in low- and middle-income countries.
These figures highlight the urgent need for comprehensive interventions to address malnutrition in all its forms. As of September 2025, the humanitarian outlook remains alarming, with growing needs far outpacing the capacity of aid agencies to respond. South Sudan…
Defining Malnutrition: The ESPEN Criteria and Weight Loss
The European Society for Clinical Nutrition and Metabolism (ESPEN) has developed criteria for diagnosing malnutrition, focusing on unintentional weight loss, reduced BMI, and low fat-free mass index (FFMI). ESPEN recommends that subjects at risk of malnutrition are identified by validated screening tools, and should be assessed and treated accordingly. Risk of malnutrition should have its own ICD Code. Second, a unanimous consensus was reached to advocate two options for the diagnosis of malnutrition. Option one requires body mass index (BMI, kg/m(2)) <18.5 to define malnutrition. Option two requires the combined finding of unintentional weight loss (mandatory) and at least one of either reduced BMI or a low fat free mass index (FFMI).
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The ESPEN criteria propose two options for diagnosing malnutrition:
BMI < 18.5 kg/m²
Unintentional weight loss (mandatory) AND at least one of the following:
- Reduced BMI: <20 kg/m² in individuals younger than 70 years, or <22 kg/m² in those older than 70 years.
- Low FFMI: <15 kg/m² in females and <17 kg/m² in males.
Weight loss thresholds:
- >10% of habitual weight, regardless of time frame
- >5% over 3 months
These criteria provide a standardized approach to identifying and diagnosing malnutrition, enabling timely intervention and treatment.
The United Nations Decade of Action on Nutrition
Recognizing the urgent need to address malnutrition, the UN General Assembly proclaimed 2016-2025 the United Nations Decade of Action on Nutrition. This initiative aims to implement commitments made at the Second International Conference on Nutrition (ICN2) and achieve global nutrition targets and diet-related NCD targets by 2025, as well as relevant targets in the Agenda for Sustainable Development by 2030.
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The Decade of Action on Nutrition, led by WHO and the Food and Agriculture Organization of the United Nations (FAO), focuses on six key areas:
- Creating sustainable, resilient food systems for healthy diets.
- Providing social protection and nutrition-related education for all.
- Aligning health systems to nutrition needs and providing universal coverage of essential nutrition interventions.
- Ensuring that trade and investment policies improve nutrition.
- Building safe and supportive environments for nutrition at all ages.
- Strengthening and promoting nutrition governance and accountability, everywhere.
WHO's Response to Malnutrition
WHO is committed to a world free of all forms of malnutrition, where all people achieve health and wellbeing. Its 2016-2025 nutrition strategy focuses on universal access to effective nutrition interventions and healthy diets from sustainable and resilient food systems.
WHO's efforts include:
- Setting, aligning, and advocating for priorities and policies that advance nutrition globally.
- Developing evidence-informed guidance based on robust scientific and ethical frameworks.
- Supporting the adoption of guidance and implementation of effective nutrition actions.
- Monitoring and evaluating policy and programme implementation and nutrition outcomes.
This work is guided by the Comprehensive implementation plan on maternal, infant, and young child nutrition, adopted by Member States in 2012.
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