Malnutrition in Adults: A Multifaceted Definition
Malnutrition is not a single condition but a broad term referring to any imbalance in a person's intake of energy and/or nutrients. It encompasses deficiencies, excesses, and imbalances, leading to a range of health issues. In adults, malnutrition can present in several ways, from being severely underweight to being obese with underlying nutrient deficiencies. The move towards standardized classification systems has been crucial for accurate diagnosis and effective intervention.
The Global Leadership Initiative on Malnutrition (GLIM) Criteria
One of the most significant advances in recent years is the consensus-based approach introduced by the Global Leadership Initiative on Malnutrition (GLIM). This framework provides a universal, two-step approach for diagnosing malnutrition in adults. First, a validated screening tool, such as the Malnutrition Universal Screening Tool (MUST) or the Nutritional Risk Screening tool (NRS-2002), identifies individuals at risk. If risk is identified, a full assessment is performed using the GLIM criteria.
Diagnosing Malnutrition with GLIM
The GLIM diagnosis requires the presence of at least one phenotypic criterion and one etiologic criterion. The assessment also grades the severity as moderate (Stage 1) or severe (Stage 2) based on the phenotypic indicators.
- Phenotypic Criteria (Physical Attributes): These include non-volitional weight loss, low Body Mass Index (BMI), and reduced muscle mass. Specific thresholds define severity.
- Etiologic Criteria (Underlying Cause): These cover reduced food intake or assimilation and the presence of inflammation or disease burden.
Etiology-Based Classification
Malnutrition can also be classified based on its underlying cause, particularly the presence and severity of inflammation. This helps guide intervention and predict outcomes, especially in clinical settings.
The Three Etiologic Categories
- Starvation-Related Malnutrition: Chronic, simple starvation without significant inflammation, often linked to social factors or eating disorders.
- Chronic Disease-Related Malnutrition: Associated with chronic illnesses and mild to moderate inflammation, such as cancer or COPD.
- Acute Disease or Injury-Related Malnutrition: Occurs with acute conditions, trauma, or severe infection accompanied by a strong inflammatory response, like burns or sepsis.
Other Forms of Adult Malnutrition
Malnutrition also encompasses specific nutrient imbalances and overnutrition.
- Micronutrient-Related Malnutrition: Deficiencies or excesses of vitamins and minerals, which can occur independently of body weight changes. Examples include iron or vitamin D deficiency.
- Overnutrition (Overweight and Obesity): Excessive fat accumulation impairing health, resulting from an energy intake/expenditure mismatch. Individuals with obesity can also have micronutrient deficiencies, known as the 'double burden'.
Comparison of Malnutrition Classification Systems
Different systems assess malnutrition using various criteria. The table below compares some modern approaches.
| Feature | Global Leadership Initiative on Malnutrition (GLIM) | American Society for Parenteral and Enteral Nutrition (ASPEN)/Academy | Subjective Global Assessment (SGA) |
|---|---|---|---|
| Primary Focus | Combines phenotypic (physical) and etiologic (cause) criteria for a comprehensive diagnosis. | Considers a set of six clinical characteristics, focusing on physical findings and intake. | Clinical and history-based assessment by a trained professional. |
| Key Criteria | Phenotypic: weight loss, low BMI, reduced muscle mass. Etiologic: reduced intake, inflammation/disease. | Insufficient energy intake, weight loss, fat/muscle loss, fluid accumulation, handgrip strength. | History (weight change, intake, GI symptoms) and physical exam (fat, muscle, edema). |
| Role of Inflammation | A core etiologic criterion, used to categorize the type of malnutrition (e.g., chronic disease). | Considered an etiologic factor that influences the severity classification. | Not a primary component, but disease burden is assessed via history. |
| Assessment Type | Objective anthropometric measurements (BMI, weight, BIA) combined with clinical judgment. | Combination of objective measures, clinical observation, and physical examination. | Entirely clinical and subjective, based on patient interview and physical exam. |
Conclusion
The classification of malnutrition in adults has evolved to a more sophisticated, evidence-based process. Modern systems like GLIM provide a standardized framework that considers both the physical signs (phenotypic) and the underlying causes (etiologic), including inflammation. This shift allows for a more accurate and nuanced diagnosis. Proper identification and classification of malnutrition are critical steps toward implementing targeted and effective nutritional interventions that improve patient outcomes. The move toward global consensus on these diagnostic criteria will ultimately strengthen clinical practice and research efforts in nutrition worldwide. Learn more about the GLIM criteria through the academic resource at Frontiers in Nutrition.
