What are the causes of protein-calorie malnutrition?

October 26, 2025 •

4 min read

Worldwide, it is estimated that undernutrition, a major component of protein-calorie malnutrition (PCM), is linked to nearly half of all deaths among children under five. The question, what are the causes of protein-calorie malnutrition?, has a complex answer, involving a mix of social, environmental, and medical factors that lead to inadequate intake or poor utilization of protein and energy.

Quick Summary

Protein-calorie malnutrition stems from a complex interplay of insufficient nutrient intake, underlying chronic diseases, and increased metabolic demands. It primarily affects vulnerable populations like children and the elderly, often worsened by socioeconomic factors like poverty and food insecurity. Both direct dietary deficiencies and impaired nutrient absorption contribute significantly to this serious condition.

Key Points

Inadequate Food Intake: Poverty, food insecurity, and poor infant feeding practices like ineffective weaning are primary causes of PCM, particularly in children and vulnerable communities.
Malabsorptive Disorders: Conditions affecting the digestive tract, such as Crohn's disease, pancreatic insufficiency, and chronic diarrhea, can lead to PCM by preventing proper nutrient absorption.
Chronic Illnesses and Cachexia: Diseases like cancer, AIDS, and chronic organ failures increase the body's metabolic demands and can cause severe wasting (cachexia), leading to secondary PCM.
Increased Metabolic Demands: Acute stressors like burns, major trauma, or severe infections trigger a hypermetabolic state that rapidly depletes the body's protein and energy stores.
Psychosocial Factors: In developed nations, depression, dementia, and eating disorders can lead to reduced appetite and intake, making the elderly and mentally ill especially vulnerable.
Vicious Cycle of Infection: Malnutrition weakens the immune system, increasing susceptibility to infections, which further worsen malnutrition by increasing metabolic needs and reducing appetite.

Protein-calorie malnutrition (PCM), also known as protein-energy malnutrition (PEM), is a severe deficiency of dietary protein and energy that impairs normal physiological processes. While it is most visible in resource-limited countries, it also affects hospitalized and institutionalized individuals in developed nations. The causes are typically categorized as either primary, resulting from an inadequate diet, or secondary, arising from other diseases or conditions.

Primary Causes: Inadequate Dietary Intake

The most straightforward and globally widespread cause of PCM is simply not consuming enough calories and protein. This can be influenced by a variety of socio-economic and behavioral factors. A diet that is quantitatively inadequate in either calories, protein, or both will result in a primary PCM condition.

Poverty and Food Insecurity: The leading cause of undernutrition in low- and middle-income countries, poverty limits access to nutritious foods. Globally, billions are food insecure, leaving them without reliable access to sufficient quantities of food.
Poor Infant and Child Feeding Practices: This includes ineffective weaning, where infants are moved from nutrient-rich breast milk to carbohydrate-heavy, protein-deficient staples like cassava or yams. This can lead to kwashiorkor, a form of PCM characterized by edema. Reduced breastfeeding and poor weaning are major factors.
Socio-Psychological Factors: For older adults, social isolation, depression, dementia, and difficulty shopping or preparing meals can significantly reduce food intake. Eating disorders like anorexia nervosa are also direct causes of starvation-related PCM.
Environmental Factors: Natural disasters, drought, and civil unrest can lead to widespread food shortages and famine. In such conditions, entire populations are at risk of severe PCM.

Secondary Causes: Disease and Increased Needs

Secondary PCM occurs when intake might be adequate but the body's ability to use or retain nutrients is compromised by another condition. This is particularly prevalent in healthcare settings.

Gastrointestinal and Malabsorptive Disorders

Certain digestive conditions prevent the body from properly breaking down or absorbing nutrients, leading to malnutrition despite an adequate diet.

Inflammatory Bowel Diseases: Conditions like Crohn's disease and ulcerative colitis cause inflammation in the intestines, impairing nutrient absorption.
Pancreatic Insufficiency: Insufficient pancreatic enzymes interfere with the digestion of fat, protein, and carbohydrates.
Chronic Diarrhea: Persistent diarrhea, often caused by infections or gut issues, leads to increased nutrient loss from the body.
Bariatric Surgery: Surgical procedures for weight loss can alter the digestive tract, resulting in malabsorption if not properly managed.

Chronic and Catabolic Illnesses

These conditions can increase the body's metabolic demands, leading to a state of chronic wasting (cachexia) even with normal food intake.

Cancer: Tumors can produce substances that increase energy expenditure and cause anorexia, leading to severe malnutrition.
AIDS and Other Chronic Infections: Infectious diseases, such as AIDS, measles, and tuberculosis, increase the body's metabolic needs and suppress appetite.
Organ Failure: Chronic kidney or liver disease can interfere with nutrient metabolism and increase protein loss.
Chronic Obstructive Pulmonary Disease (COPD): Patients with severe COPD often experience breathlessness, making eating difficult and energy expenditure high.

Increased Metabolic Needs Due to Acute Stress

Acute illnesses or injuries can dramatically increase the body's demand for protein and calories, quickly leading to PCM if not addressed.

Burns: Extensive burns significantly increase metabolic rate and protein turnover, requiring very high caloric and protein intake for healing.
Trauma and Surgery: Major trauma or surgery triggers a hypermetabolic state as the body works to repair tissues.
Severe Infection: Fevers and sepsis drive up energy requirements to fight off the infection, contributing to muscle and fat wasting.

Comparison of Primary and Secondary PCM Causes


Feature	Primary PCM	Secondary PCM
Root Cause	Inadequate access to or intake of food.	An underlying disease or medical condition.
Dietary Context	Diet is insufficient in quantity and/or quality of nutrients.	Intake may be adequate, but absorption, metabolism, or requirements are impaired.
Typical Population	Children and elderly in resource-limited settings; impoverished groups.	Hospitalized patients, individuals with chronic illnesses (e.g., cancer, AIDS), and those with malabsorptive disorders.
Examples	Famine, poor breastfeeding practices, depression leading to low appetite.	Inflammatory bowel disease, end-stage renal disease, severe burns.

The Vicious Cycle of Malnutrition and Infection

One of the most dangerous aspects of PCM is its link with infectious diseases. Malnutrition weakens the immune system, making individuals more susceptible to infections like pneumonia, measles, and diarrhea. These infections, in turn, increase metabolic needs, cause loss of appetite, and reduce nutrient absorption, exacerbating the malnutrition. This creates a vicious cycle that can be life-threatening, especially for children.

Conclusion: A Multifaceted Problem Requiring a Comprehensive Approach

In conclusion, the causes of protein-calorie malnutrition are multifaceted, encompassing both environmental and medical triggers. Addressing this condition requires more than just increasing food intake; it necessitates a comprehensive approach that tackles underlying social issues like poverty and educational gaps, as well as managing complex medical conditions that interfere with nutrient absorption and metabolism. Early identification and tailored nutritional interventions are critical for improving outcomes and preventing long-term damage, particularly in vulnerable populations like children and the elderly. A multi-pronged public health strategy is essential for breaking the cycle of malnutrition and infection and promoting better global health.

Learn more about malnutrition from reliable health authorities. The World Health Organization offers extensive information on the global challenge of malnutrition and its various forms, providing crucial context for understanding the scope of this issue.

Frequently Asked Questions

Marasmus is a form of PCM caused by a severe deficiency of both calories and protein, leading to extreme wasting of muscle and fat. Kwashiorkor, on the other hand, is primarily caused by a severe protein deficiency with relatively adequate calorie intake, resulting in fluid retention (edema) and a swollen abdomen.

While PCM is a major concern in children in resource-limited countries, it can affect people of any age worldwide. In developed nations, it is often seen in hospitalized patients, the elderly in institutional care, and individuals with chronic diseases.

Yes, psychiatric conditions can be a significant cause of PCM. Eating disorders like anorexia nervosa lead to severe dietary restriction. Additionally, depression and dementia, particularly in the elderly, can cause a loss of appetite and reduced motivation to eat or prepare food.

Chronic infections, such as AIDS, increase the body's metabolic needs to fight the illness while also often causing fever, diarrhea, and appetite loss. This combination rapidly depletes the body's protein and energy reserves, leading to severe malnutrition.

Hospitalized patients, especially those who are elderly or critically ill, are at high risk. They may have increased metabolic demands from their illness or injury, decreased appetite, or difficulty feeding themselves. This can lead to a rapid onset of PCM, worsening their condition.

Yes, a person can be overweight and malnourished simultaneously, a phenomenon known as the 'double burden of malnutrition'. This can happen if their diet, while high in calories, is deficient in essential micronutrients like vitamins and minerals.

While PCM is defined by macronutrient deficiency, it is almost always accompanied by micronutrient deficiencies, which also cause severe health problems. For example, zinc deficiency is linked to skin lesions and impaired immunity, while iron deficiency can cause anemia.

In developed countries, low-income communities may have easier access to high-calorie, low-nutrient fast food than to nutritious whole foods. This can lead to a form of malnutrition where caloric needs are met or exceeded, but essential protein and micronutrients are lacking.

Yes, large-scale environmental factors like drought, war, and civil unrest can disrupt food production and distribution, leading to widespread food shortages and famine, a major cause of primary PCM.