The FAO's Methodology for Minimum Dietary Energy
The Food and Agriculture Organization of the United Nations (FAO), in collaboration with the World Health Organization (WHO) and the United Nations University (UNU), developed the methodology for calculating Minimum Dietary Energy Requirements (MDER) to assess food deprivation. This calculation is foundational to estimating the prevalence of undernourishment (PoU) in different countries and tracking progress toward food security goals. The MDER represents the minimum amount of dietary energy that is considered adequate to meet the energy needs of a person at a minimum acceptable body mass index (BMI) for their height, assuming a sedentary lifestyle.
Factors Influencing the Calculation
The MDER is not a fixed, one-size-fits-all number. It is a dynamic figure that reflects demographic and physiological variations within a population. The calculation considers several key factors:
- Age and Sex: The energy needs of individuals change significantly throughout their lifespan. For instance, children have different requirements for growth and development, while adults' needs vary based on age and gender. The FAO uses data on the age and sex distribution of a country's population to create a weighted average of energy requirements.
- Body Weight and Height: The body mass of a person is a major determinant of their Basal Metabolic Rate (BMR), which is the energy needed to support the body at rest. The FAO's methodology incorporates body weight for attained height, with calculations based on WHO reference tables.
- Physical Activity Level (PAL): The calculation assumes a sedentary lifestyle, which is the lowest level of physical activity. This allows the FAO to establish a minimal energy threshold, below which a person is considered undernourished.
- Pregnancy Allowance: A pregnancy allowance is also added to the overall minimum daily energy requirement for the population to account for the increased energy needs of pregnant women.
The Calculation Process
The FAO's process for determining the MDER for a population is a multi-step, technical process:
- Collect Demographic Data: The first step is to gather data on the population's structure by sex and age. This information is drawn from sources like the UN Department of Economic and Social Affairs (DESA).
- Determine Reference Body Weights: Using median height data from anthropometric surveys, reference body weights are established for each age and sex group based on WHO BMI standards.
- Calculate Basal Metabolic Rate (BMR): The BMR for adults in each group is estimated using sex and age-specific regression equations, such as the Schofield equations, based on their reference body weight.
- Incorporate Physical Activity Level (PAL): For the minimum requirement, the BMR is multiplied by a Physical Activity Level (PAL) factor that represents a sedentary lifestyle to derive the energy needs for each group.
- Aggregate into Overall MDER: The minimum energy requirements for each sex and age group are then aggregated and weighted by the proportion of each group in the total population. A pregnancy allowance is added to this figure.
Comparison of FAO's Minimum Requirement vs. General Recommendations
Understanding the distinction between the FAO's MDER and general nutritional advice is crucial. The MDER is a benchmark for population-level assessment, not a dietary target for individuals. General health recommendations, like those from the US Dietary Guidelines, often provide a broader range for healthy individuals with varying activity levels.
| Feature | FAO Minimum Dietary Energy Requirement (MDER) | General Dietary Recommendations (e.g., DGA) |
|---|---|---|
| Purpose | To measure population-level food deprivation and track undernourishment. | To guide healthy eating for individuals based on age, sex, and activity level. |
| Calculation | A weighted average based on a population's age, sex, height, and body weight, assuming a sedentary lifestyle. | A range of calories designed for active, healthy individuals to maintain or achieve a healthy weight. |
| Usage | Exclusively for statistical purposes and policy-making on food security. | A practical guide for individuals planning their daily nutritional intake. |
| Focus | Identifying the lowest survival threshold at a population level. | Promoting a healthy lifestyle and preventing diet-related diseases. |
Limitations and Considerations
The FAO's MDER is an essential tool for global monitoring, but it has important limitations that must be understood. Since it is a weighted average based on national data, it masks the significant inequalities in access to food that can exist within a country. A country with an average caloric intake above the MDER can still have large segments of its population suffering from undernourishment, particularly if there is a high degree of inequality in food distribution. The figure also represents a baseline for survival, not optimal health. Therefore, consuming the MDER amount of calories does not guarantee good health, as factors like nutritional quality, variety of diet, and micronutrient intake are not considered in this specific metric.
Implications of Undernourishment
The FAO uses the MDER as a cut-off point to define undernourishment. When a person's habitual food intake falls below this minimum level, they are considered undernourished. The consequences of this condition are severe and include:
- Reduced Productivity: Insufficient energy intake impairs labor productivity, which can trap individuals and communities in poverty.
- Impaired Development: In children, undernourishment can seriously affect physical and mental development, leading to long-term health problems.
- Increased Risk of Illness: A weakened immune system makes individuals more susceptible to diseases and infections.
- Higher Mortality Rates: Severe and prolonged undernourishment can lead to premature death, particularly among vulnerable groups like children.
Conclusion
The minimum calorie intake according to FAO, known as the Minimum Dietary Energy Requirement (MDER), is a statistically derived and context-specific measure used to estimate the prevalence of undernourishment at a national level. It is not a fixed number but a dynamic figure calculated based on a population's demographics, including age, sex, body weight, and height, assuming a sedentary lifestyle. This metric is a crucial tool for global food security monitoring and policymaking, highlighting areas where food availability is a significant concern. However, it is important to remember that it represents a baseline for survival, not optimal health, and does not capture the full scope of nutritional well-being or food access inequality within a population. For a complete picture of human energy requirements, it is necessary to consult more detailed nutritional guidelines that account for varied lifestyles, health statuses, and dietary quality, such as those published by the FAO itself in its broader body of work on human energy requirements.
