What Causes Lack of Protein and Energy?

November 15, 2025 •

5 min read

According to the World Health Organization, nearly half of all deaths among children under five are linked to undernutrition. This severe form of malnutrition, known as protein-energy malnutrition (PEM), results from a significant lack of both protein and energy. A deficiency can occur due to insufficient food intake, underlying health issues, or increased nutritional demands, affecting individuals across all ages and demographics.

Quick Summary

This article explores the multifaceted causes behind protein and energy deficiencies, ranging from inadequate dietary intake to underlying medical conditions and increased metabolic demands. It details how malabsorption, infections, and certain medications can interfere with nutrient utilization, leading to serious health consequences, and provides a clear breakdown of the factors involved.

Key Points

Poor Diet: The most common cause is simply not consuming enough calories and protein, often due to food insecurity, poverty, or eating disorders.
Malabsorption Disorders: Conditions like celiac disease and inflammatory bowel disease prevent the body from absorbing nutrients effectively, even with adequate intake.
Increased Metabolic Demands: Critical illnesses, severe infections, trauma, and hyperthyroidism can dramatically increase the body's need for protein and energy.
Organ Dysfunction: Liver and kidney diseases can impair the body's ability to synthesize proteins or lead to excessive protein loss, respectively.
Aging and Risk Factors: The elderly are highly susceptible due to decreased appetite, chronic illnesses, and reduced nutrient absorption.
Lifestyle and Mental Health: Factors such as chronic stress, sleep deprivation, and depression can contribute to a lack of energy and appetite.

Understanding Protein-Energy Malnutrition

Protein-energy malnutrition (PEM) is a serious and complex health issue resulting from insufficient intake of both protein and calories. While most people in developed nations consume adequate protein, certain factors can still lead to a deficiency. Understanding the root causes is the first step toward effective prevention and treatment.

Inadequate Dietary Intake

The most straightforward cause of a lack of protein and energy is simply not eating enough food or not eating the right types of food. This can manifest in several ways across different populations:

Food Insecurity and Poverty: In developing countries, limited access to sufficient, nutritious food is a primary driver of PEM, particularly among children. This can be exacerbated by ineffective weaning, poor hygiene, and contaminated food sources.
Eating Disorders: Conditions like anorexia nervosa can cause a severe reduction in food intake, leading to significant deficiencies in both protein and energy.
Restricted Diets: Vegans and vegetarians who do not plan their diets carefully may be at risk if they don't consume a variety of complementary plant-based protein sources. Fad diets that severely restrict food groups can also lead to nutrient deficiencies.
Depression and Isolation: In older adults, depression and social isolation can lead to decreased appetite and inadequate nutrient intake, contributing to malnutrition.
Anorexia of Aging: Frail older individuals often experience a natural decrease in appetite, along with other factors like poor dentition and difficulty preparing meals, which contributes to poor nutritional status.

Comparing Causes of Deficiency


Feature	Inadequate Intake	Malabsorption Issues	Increased Metabolic Demands
Primary Cause	Lack of sufficient food or poor dietary choices.	Inability to absorb nutrients from consumed food.	Elevated calorie and protein needs due to illness or trauma.
Key Examples	Poverty, eating disorders, unplanned vegan diets.	Celiac disease, Crohn's disease, pancreatic insufficiency.	Major infections, severe burns, critical illness, cancer.
Population at Risk	Children and elderly in low-income areas; individuals with eating disorders.	Patients with gastrointestinal disorders; post-bariatric surgery patients.	Individuals with chronic illnesses or recent trauma.
Metabolic Shift	Body breaks down fat and muscle for energy.	Nutrients are lost before they can be used by the body.	Body uses up protein and energy at an accelerated rate.

Underlying Health Conditions

Beyond dietary factors, a range of medical conditions can cause a lack of protein and energy by impairing the body's ability to digest, absorb, or metabolize nutrients.

Malabsorption Disorders

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis cause chronic inflammation of the digestive tract, which can damage the intestinal lining and hinder nutrient absorption.
Celiac Disease: This autoimmune disorder damages the small intestine when gluten is ingested, leading to poor absorption of nutrients, including protein.
Pancreatic Insufficiency: A reduced output of pancreatic enzymes can impair digestion and absorption of fats and proteins.
Gastrointestinal Surgery: Procedures such as bariatric surgery can alter the digestive process, leading to nutrient malabsorption.

Increased Metabolic Needs

Certain health states significantly increase the body's demand for protein and energy, which can lead to a deficiency if intake doesn't keep pace.

Chronic Diseases: Conditions such as cancer, chronic obstructive pulmonary disease (COPD), heart failure, and renal failure can cause systemic inflammation and muscle wasting (cachexia), which increases nutrient needs.
Acute Illnesses and Trauma: Severe infections (e.g., sepsis), extensive burns, or major surgery trigger a massive inflammatory response that increases metabolic rate and protein breakdown.
Hyperthyroidism: An overactive thyroid gland accelerates the body's metabolism, increasing the demand for calories and protein.
Pregnancy and Lactation: These physiological states require a higher intake of protein and calories to support the mother and developing child.

Other Systemic Issues

Liver Disease: The liver is crucial for synthesizing proteins. In conditions like cirrhosis, liver dysfunction can lead to low protein levels in the blood.
Kidney Disease: The kidneys regulate protein balance. In nephrotic syndrome, large amounts of protein can be lost in the urine, causing a deficiency.
Infections: Chronic or recurrent infections can lead to inflammation and increase the body's need for protein and energy, while simultaneously decreasing appetite.

Conclusion

A lack of protein and energy is not always a simple issue of diet but often a complex interplay of nutritional, physiological, and environmental factors. From the severe food insecurity that causes Kwashiorkor and Marasmus in children to chronic diseases and advanced age in developed nations, the root causes are varied. Addressing this requires a multi-pronged approach that includes dietary adjustments, management of underlying medical conditions, and, for some, addressing social and economic barriers to nutritious food. Recognizing the signs, understanding the risks, and seeking expert medical and nutritional advice is crucial for preventing and treating these deficiencies effectively. For more comprehensive information on dietary protein, consult reliable sources like the Harvard T.H. Chan School of Public Health's The Nutrition Source.

Taking Action Against Deficiency

Prioritize Dietary Variety: Ensure your diet includes a balance of protein sources (lean meats, fish, eggs, dairy, legumes, nuts, seeds), complex carbohydrates, and healthy fats.
Manage Underlying Conditions: Work with healthcare providers to control chronic diseases like IBD, liver, or kidney issues that impact nutrient absorption and metabolism.
Monitor Vulnerable Groups: Pay close attention to the nutritional needs of children, pregnant women, and the elderly, who are at higher risk of developing deficiencies.
Preventative Healthcare: Regular check-ups can help identify deficiencies early through laboratory tests, such as measuring serum albumin levels.
Seek Professional Guidance: For those on restrictive diets or with severe symptoms, a registered dietitian can create a safe and effective dietary plan.

Addressing Causes of Fatigue and Weakness

Optimize Sleep: Ensure sufficient, high-quality sleep, as sleep deprivation is a major contributor to fatigue.
Stay Hydrated: Dehydration can cause feelings of low energy. Drink plenty of water throughout the day to support metabolic functions.
Incorporate Physical Activity: Regular exercise, even in moderate amounts, can boost energy levels and improve overall well-being.
Assess Iron Levels: Iron deficiency (anemia) can lead to profound fatigue. If you suspect low iron, a blood test and a diet rich in iron-fortified foods may be necessary.
Consult a Doctor: If fatigue is persistent despite lifestyle changes, it could signal a more serious underlying medical or mental health condition.

Frequently Asked Questions

PEM, also known as protein-energy undernutrition, is a condition resulting from an insufficient intake of both protein and calories. In severe cases, it can be life-threatening and is often categorized into Kwashiorkor (protein deficiency with edema) and Marasmus (severe calorie and protein deficiency leading to wasting).

Yes. Malnutrition can occur in individuals who are overweight or have a normal BMI, but consume a diet high in calories yet lacking in essential nutrients like protein, vitamins, and minerals. This is often referred to as 'overnutrition with micronutrient undernutrition'.

Infections increase metabolic demands, requiring more energy and protein to fight off the illness. They can also cause anorexia, diarrhea, or vomiting, which further reduces nutrient intake and absorption. This creates a vicious cycle where malnutrition weakens the immune system, making a person more susceptible to future infections.

Yes, several groups are at higher risk. These include children, pregnant women, the elderly, individuals with chronic illnesses like cancer or kidney disease, and people living in poverty or food-insecure regions.

Symptoms can vary but commonly include fatigue and weakness, loss of muscle mass, edema (swelling), brittle hair and nails, skin problems, stunted growth in children, increased frequency of infections, and mood changes.

Treatment depends on the severity and cause. Mild deficiencies can be corrected with a balanced diet, while severe cases, especially in children, may require hospitalization, fluid and electrolyte management, and carefully controlled nutritional rehabilitation to avoid refeeding syndrome.

A poorly planned vegetarian or vegan diet can lead to a protein deficiency, as animal products are complete protein sources. However, a well-planned diet that includes a variety of plant-based protein sources like legumes, lentils, nuts, seeds, and whole grains can easily provide all necessary amino acids.