Nutrition Insights: What is the best definition of undernutrition?

November 1, 2025 •

3 min read

According to the World Health Organization (WHO), undernutrition is one of the two broad groups of conditions encompassed by malnutrition and affects millions worldwide, including 149 million children under five who are stunted. Understanding what is the best definition of undernutrition? is crucial for identifying and addressing the health and development challenges it poses.

Quick Summary

Undernutrition is a complex nutritional deficiency resulting from insufficient intake or poor absorption of energy and nutrients. It includes forms like stunting, wasting, underweight, and micronutrient deficiencies, leading to serious health impacts.

Key Points

WHO's Definition: The World Health Organization defines undernutrition as a subgroup of malnutrition that includes deficiencies in a person's intake of energy and nutrients.
Four Main Forms: Undernutrition presents as wasting, stunting, underweight, and micronutrient deficiencies, each with distinct causes and effects.
Acute vs. Chronic: Wasting indicates acute nutritional deficiency, often due to recent and severe weight loss, while stunting reflects chronic, long-term deprivation.
Complex Causes: The causes extend beyond food scarcity to include illness, poor sanitation, inadequate care practices, and broader socioeconomic and political factors.
Holistic Solutions: Addressing undernutrition requires comprehensive, multi-sectoral interventions that target both immediate nutritional needs and underlying social determinants of health.

Defining Undernutrition: A Comprehensive Approach

The World Health Organization (WHO) defines undernutrition as a condition resulting from insufficient intake of energy and nutrients. It's a group of conditions encompassing four main forms: wasting, stunting, underweight, and micronutrient deficiencies. This definition is vital for understanding and addressing the various ways nutritional deficits impact health.

The Four Forms of Undernutrition

Wasting (Low Weight-for-Height): Characterized by recent and severe weight loss, often due to inadequate intake or illness. It's a form of acute malnutrition and increases the risk of death, though recovery is possible with treatment.
Stunting (Low Height-for-Age): This reflects chronic or recurrent undernutrition, linked to factors like poor socioeconomic conditions and recurrent illness in early life. Stunting is a long-term condition that can impair physical and cognitive development.
Underweight (Low Weight-for-Age): A child with low weight for their age may be stunted, wasted, or both.
Micronutrient Deficiencies: Also known as 'hidden hunger,' this is a lack of essential vitamins and minerals crucial for growth, development, and immune function.

Causes of Undernutrition

Undernutrition stems from a complex mix of immediate, underlying, and basic factors, as outlined in the UNICEF framework.

Immediate Causes

Inadequate Dietary Intake: Not consuming enough energy and nutrients, especially critical during periods of rapid growth.
Disease: Frequent infections can lead to poor nutrient absorption and increased nutrient needs.

Underlying and Basic Causes

Food Insecurity: Limited access to nutritious food due to poverty.
Inadequate Care: Poor feeding practices, particularly in young children.
Unhealthy Environment: Lack of clean water, sanitation, and health services increases exposure to pathogens that hinder nutrient absorption.
Socioeconomic and Political Factors: Broader issues like instability and inequality contribute to food insecurity.

Acute vs. Chronic Undernutrition: A Comparison

Understanding the difference between acute and chronic undernutrition is key. Wasting represents acute undernutrition, while stunting signifies chronic undernutrition.


Feature	Acute Undernutrition (Wasting)	Chronic Undernutrition (Stunting)
Onset	Recent and severe	Long-term and recurrent
Cause	Sudden insufficient food intake, infectious disease	Prolonged nutritional deprivation
Indicator	Low weight-for-height (WHZ or WLZ below -2 SD)	Low height-for-age (HAZ below -2 SD)
Consequences	High risk of mortality, weakened immune system	Impaired cognitive development, reduced intellectual capacity
Timeframe	Indicates current and immediate nutritional crisis	Reflects past and ongoing nutritional status

Managing and Addressing Undernutrition

Addressing undernutrition requires comprehensive interventions. A diagonal approach combining targeted programs with broader health system improvements is often recommended. Interventions can include improving food security, enhancing maternal and child nutrition programs, ensuring access to clean water and sanitation, providing nutrition education, and implementing supplementary feeding programs. Focusing on nutrition during the first 1,000 days of life is particularly crucial.

Conclusion

In conclusion, the best definition of undernutrition? is the one provided by the WHO, which identifies it as a condition of insufficient energy and nutrient intake with forms including wasting, stunting, underweight, and micronutrient deficiencies. Tackling this complex issue requires a holistic strategy addressing immediate needs and underlying social, economic, and environmental factors. Targeting early-life nutrition and implementing integrated public health strategies are essential for reducing the burden of undernutrition and improving global health.

For more detailed information on global nutrition strategies and targets, visit the World Health Organization website [https://www.who.int/news-room/fact-sheets/detail/malnutrition].

Frequently Asked Questions

Malnutrition is a broader term covering deficiencies, excesses, or imbalances in nutrient intake. Undernutrition is a subgroup of malnutrition that specifically refers to deficiencies, while malnutrition also includes overweight and obesity.

The four main types of undernutrition are wasting (low weight-for-height), stunting (low height-for-age), underweight (low weight-for-age), and micronutrient deficiencies (lack of essential vitamins and minerals).

The long-term effects can be severe, particularly from chronic undernutrition like stunting. These include delayed mental development, reduced intellectual capacity, and poor physical performance, which can affect national productivity.

In children, undernutrition is often diagnosed using anthropometric measurements such as weight-for-height, height-for-age, and weight-for-age compared to WHO growth standards. Clinical signs like nutritional edema are also used.

Yes, it is possible for an individual to be both overweight and micronutrient deficient, a phenomenon that is part of the 'double burden of malnutrition.' This occurs when a diet high in energy-dense foods is low in vitamins and minerals.

In these regions, primary causes include insufficient food supply due to socioeconomic and environmental factors, poor nutrition for pregnant women, inadequate feeding practices, and frequent infectious illnesses exacerbated by poor sanitation.

The WHO, in collaboration with partners like UNICEF, advocates for policies, develops evidence-based guidance, and supports interventions to improve nutrition globally. Their strategies focus on healthy diets, sustainable food systems, and targeted interventions.