What Classifies Someone as Malnourished?

November 15, 2025 •

4 min read

According to the World Health Organization (WHO), malnutrition encompasses deficiencies, excesses, or imbalances in a person's intake of energy and/or nutrients. It is a serious condition that can be difficult to recognize, as it includes both undernutrition and overnutrition. This broader definition helps classify someone as malnourished by considering all forms of poor nutrition, not just insufficient intake.

Quick Summary

This guide details the classifications, signs, and symptoms of malnutrition, explaining the differences between undernutrition and overnutrition. It also covers common causes and the diagnostic process.

Key Points

Broad Definition: Malnutrition includes deficiencies, excesses, or imbalances in nutrient intake, covering both undernutrition and overnutrition.
Undernutrition: This encompasses wasting (low weight-for-height), stunting (low height-for-age), and micronutrient deficiencies, commonly known as hidden hunger.
Overnutrition: This form involves excessive intake of nutrients, often leading to overweight and obesity, which increases the risk of chronic diseases like diabetes.
Key Signs: Red flags for malnutrition include unintentional weight loss, reduced appetite, constant fatigue, slow healing, and, in children, faltering growth.
Diagnosis Process: Classification involves a physical exam, diet history, and potential lab work, with screening tools like MUST used for adults.
Underlying Causes: Factors such as poverty, chronic illness, sedentary lifestyles, and poor access to nutritious food contribute significantly to malnutrition.

The concept of malnutrition extends beyond simply not having enough food. It is a complex issue affecting people of all sizes and ages, and its definition has evolved to include multiple forms of nutritional imbalance. Understanding the specific classifications of malnutrition is crucial for accurate diagnosis and effective intervention.

Undernutrition: The Classic Form of Malnutrition

Undernutrition is what most people associate with the term malnutrition, resulting from a deficit of energy and nutrients. It manifests in several sub-forms, including:

Wasting: Low weight-for-height, often indicating a recent and severe weight loss due to starvation or infectious diseases like diarrhea. It can lead to a dangerously low body mass index (BMI).
Stunting: Low height-for-age, resulting from chronic or recurrent undernutrition in early life. It is frequently associated with poor socioeconomic conditions and recurrent illnesses, preventing children from reaching their full physical and cognitive potential.
Underweight: Low weight-for-age, which can be a combination of both wasting and stunting.
Micronutrient Deficiencies: Also known as hidden hunger, this occurs when there is a lack of essential vitamins and minerals, even if a person consumes enough calories. Common deficiencies include iron, iodine, and Vitamin A.

Overnutrition: Malnutrition in Excess

Overnutrition occurs when the intake of energy and nutrients exceeds the body's needs, often leading to obesity. This form of malnutrition is characterized by an accumulation of excessive body fat, increasing the risk of diet-related noncommunicable diseases such as heart disease, stroke, and type 2 diabetes. It is a growing global health challenge, affecting both developed and developing countries. A person can be overweight or obese and still suffer from micronutrient deficiencies if their diet consists of energy-dense but nutrient-poor foods.

Common Signs and Symptoms

Diagnosing malnutrition involves more than just a person's weight. A comprehensive assessment considers a range of physical, behavioral, and physiological signs.

Common indicators of malnutrition include:

Unintentional weight loss: Losing 5–10% or more of one's body weight over a 3–6 month period is a significant indicator.
Reduced appetite: A general lack of interest in eating and drinking.
Fatigue and weakness: Feeling constantly tired or weak, even after resting.
Slow recovery: Taking longer to heal from wounds or recover from illnesses.
Poor concentration: Difficulty focusing or maintaining attention.
Changes in skin and hair: Dry, inelastic skin or brittle hair that falls out easily.
Growth issues in children: Faltering growth, slow development, or an inability to gain weight at the expected rate.
Edema: Swelling, particularly in the legs and abdomen, is a sign of severe protein deficiency, as seen in Kwashiorkor.

Comparison of Malnutrition Types


Feature	Undernutrition	Overnutrition
Energy & Nutrient Intake	Deficient in energy and/or essential nutrients.	Excessive intake of energy and/or specific nutrients.
Body Composition	Loss of fat, muscle mass, and body tissue.	Excessive body fat accumulation, leading to overweight or obesity.
Nutrient Balance	Inadequate amounts of macronutrients (protein, carbs) and/or micronutrients (vitamins, minerals).	Excessive intake of macronutrients; can still have micronutrient deficiencies if diet is poor.
Health Consequences	Impaired immune function, stunted growth, wasting, increased risk of infection, apathy.	Increased risk of diabetes, heart disease, high blood pressure, and certain cancers.
Common Causes	Poverty, food insecurity, chronic illness, malabsorption disorders, eating disorders.	Sedentary lifestyle, high intake of energy-dense foods, hormonal imbalances, psychological stress.
Observable Features	Visible wasting, low BMI, fatigue, irritability, slow recovery from illness.	Overweight/obesity, high blood pressure, insulin resistance.

The Role of Diagnosis

Formal diagnosis typically begins with a physical examination and a review of the patient's medical history, dietary habits, and social situation. For adults, screening tools like the Malnutrition Universal Screening Tool (MUST) can be used to assess risk. Further evaluation may include blood tests to measure levels of specific vitamins, minerals, and proteins like albumin. In children, growth measurements like weight-for-height and height-for-age are critical indicators.

Conclusion: A Multifaceted Problem

Classifying someone as malnourished is a multifaceted process that recognizes the full spectrum of nutritional imbalance. It is not limited to the visibly underweight but also includes those who are overweight or obese due to poor dietary quality. From undernutrition causing stunting and wasting to overnutrition leading to chronic noncommunicable diseases, the global burden of malnutrition is a significant public health challenge. Early detection through a combination of physical signs, diagnostic tests, and risk factor assessment is key to successful treatment and prevention. The ultimate goal is to achieve proper nutrition for everyone, addressing both deficiencies and excesses to ensure overall health and well-being.

For more detailed information on specific guidelines and global efforts to combat malnutrition, authoritative sources like the World Health Organization (WHO) are invaluable. World Health Organization (WHO) | Fact sheets - Malnutrition

Frequently Asked Questions

Yes, it is possible to be overweight or obese and still be malnourished. This happens when a person consumes excessive calories from energy-dense, nutrient-poor foods, leading to overnutrition while simultaneously suffering from micronutrient deficiencies.

Stunting is low height-for-age and is caused by chronic, long-term undernutrition. Wasting is low weight-for-height and indicates a recent and severe weight loss.

Some of the first signs of malnutrition include unintentional weight loss, loss of appetite, persistent tiredness, and a general feeling of weakness.

In children, diagnosis relies heavily on growth measurements, including weight-for-height, height-for-age, and head circumference, as faltering growth is a key indicator. For adults, BMI and recent unintentional weight changes are significant.

'Hidden hunger' is another term for micronutrient deficiencies, which occur when a person lacks essential vitamins and minerals, such as iron, vitamin A, and zinc, even if they are getting enough calories overall.

A variety of medical conditions can increase the risk of malnutrition, including chronic illnesses like Crohn's disease, AIDS, cancer, and dementia, which can affect appetite or nutrient absorption.

Yes, malnutrition is treatable, with interventions varying based on the type and severity. Treatment can range from dietary modifications and nutritional supplements to addressing underlying medical conditions.