What is Now Called PEM: An Updated Terminology
For decades, medical and public health communities used the term Protein-Energy Malnutrition (PEM) to describe a range of conditions resulting from a lack of protein and energy. However, this term has been largely replaced. The more accurate and current term is Protein-Energy Undernutrition (PEU). This shift in nomenclature more precisely reflects that the condition is a deficit, or under-supply, of nutrients, as opposed to the broader term of malnutrition, which can encompass both deficiencies and excesses.
PEU encompasses conditions arising from a lack of dietary protein, energy (calories), or both, and can manifest in various degrees of severity. It is a significant global health problem, especially in low-income countries, though it also appears in hospitalized and elderly individuals in developed nations.
The Two Primary Forms of PEU
PEU primarily manifests in two classic forms, marasmus and kwashiorkor, which often exist on a spectrum, with marasmic-kwashiorkor representing a mixed state.
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Marasmus: This condition results from a severe deficiency of both protein and total calories. It is characterized by extreme wasting of muscle tissue and loss of subcutaneous fat, giving the child an emaciated, skeletal appearance, often with a prominent head relative to the body. Despite the severe wasting, edema (swelling) is typically absent. The body's metabolic rate slows significantly to conserve energy.
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Kwashiorkor: This form is caused predominantly by a protein deficiency, even when overall calorie intake may be marginal or adequate. A hallmark sign is edema, or swelling, which can affect the face, abdomen (potbelly), and extremities. This swelling can mask the underlying wasting. Other symptoms include sparse and brittle hair, skin lesions, and an enlarged, fatty liver. The name itself, derived from a Ghanaian language, means "the sickness the baby gets when the next baby is born," referring to the protein-poor diet given to an older child after weaning.
The Pathophysiology and Complications of PEU
When the body lacks sufficient energy, it first utilizes stored fat. When fat reserves are depleted, it begins breaking down lean tissue like muscle and organ mass to acquire protein and energy, leading to a negative nitrogen balance. This process severely impacts multiple bodily systems:
- Immune System: Impaired immunity increases susceptibility to infections like pneumonia and gastroenteritis, which can further worsen malnutrition.
- Cardiovascular System: Heart size and output can decrease, leading to a slower pulse and lower blood pressure.
- Gastrointestinal Tract: Mucosal atrophy and loss of intestinal villi can cause malabsorption, perpetuating the cycle of nutrient deficiency.
Distinguishing Undernutrition from Overnutrition
Malnutrition is a complex, overarching term that encompasses three broad conditions: undernutrition, overnutrition, and micronutrient-related deficiencies or excesses. Understanding the distinction between undernutrition and overnutrition is crucial for proper diagnosis and treatment.
What is Undernutrition?
Undernutrition is a form of malnutrition that results from an insufficient intake of nutrients and energy. It is what most people typically think of when they hear the term malnutrition. The primary characteristics of undernutrition include:
- Inadequate Intake: A diet lacking sufficient quantities of protein, carbohydrates, fats, vitamins, and minerals.
- Manifestations: Can present as wasting (low weight-for-height), stunting (low height-for-age), and being underweight (low weight-for-age).
- Underlying Causes: Often linked to poverty, limited access to nutritious food, infectious diseases, or medical conditions that impair nutrient absorption.
- Micronutrient Deficiencies: Can occur even with adequate calorie intake if the diet lacks variety. Common deficiencies include iron, iodine, and Vitamin A.
What is Overnutrition?
In contrast to undernutrition, overnutrition is a form of malnutrition caused by an excessive intake of nutrients or calories. This excess can be of macronutrients (leading to obesity) or, less commonly, micronutrients (leading to toxicity). Key features include:
- Excessive Intake: Consuming more energy (calories) than the body requires, leading to the storage of excess energy as body fat.
- Health Consequences: Often leads to being overweight (BMI $\ge$ 25) or obese (BMI $\ge$ 30) and is a major risk factor for diet-related noncommunicable diseases (NCDs) like type 2 diabetes, cardiovascular disease, and certain cancers.
- Dietary Shift: Frequently linked to a "nutrition transition" where traditional diets are replaced by energy-dense, high-fat, high-sugar, and low-nutrient foods common in Westernized diets.
- The Double Burden: A particularly complex issue is the "double burden of malnutrition," where undernutrition and overnutrition coexist within the same country, household, or even individual. This occurs when a diet high in calories but low in micronutrients is consumed.
Comparison Table: Undernutrition vs. Overnutrition
| Feature | Undernutrition | Overnutrition |
|---|---|---|
| Underlying Cause | Insufficient intake of energy and nutrients relative to needs. | Excessive intake of energy and nutrients relative to needs. |
| Physical Appearance | Wasting, stunting, underweight, emaciation. Can be masked by edema in kwashiorkor. | Overweight, obesity, excessive fat accumulation. |
| Dietary Pattern | Lack of access to quality, nutrient-dense foods; can include protein-poor, carbohydrate-heavy diets. | High consumption of energy-dense foods and drinks; often low in micronutrients. |
| Associated Health Risks | Impaired immunity, developmental delay, organ dysfunction, higher mortality rates. | Chronic inflammation, type 2 diabetes, cardiovascular disease, certain cancers. |
| Societal Context | More prevalent in low-income settings and areas with food insecurity, but can occur anywhere. | Common in developed countries but increasingly prevalent in urban areas of middle- and low-income countries. |
Conclusion: Malnutrition's Many Faces
In summary, the term Protein-Energy Malnutrition (PEM) has been updated to Protein-Energy Undernutrition (PEU) to be more specific about the nature of the condition. PEU represents a deficiency of protein and/or energy, manifesting as marasmus, kwashiorkor, or a combination. This stands in contrast to overnutrition, which is characterized by an excessive intake of calories leading to overweight and obesity. Both PEU and overnutrition are forms of the broader condition known as malnutrition. Recognizing that malnutrition is not solely a problem of starvation but also one of overconsumption is a critical step toward addressing the varied and complex global nutritional challenges we face today.
For more information on the global burden of malnutrition, visit the World Health Organization's nutrition fact sheets.
