The body's energy requirements are dynamic, changing with a person's age, physiological state, and lifestyle. To provide guidance, nutrition experts developed the Dietary Reference Intakes (DRIs), a set of reference values for nutrient intake. For energy, the specific DRI is the Estimated Energy Requirement (EER), an average dietary energy intake predicted to maintain energy balance in healthy individuals within a defined age, sex, weight, and physical activity group.
The Components of Total Energy Expenditure
To estimate energy needs, it's essential to understand where the body uses its energy. Total Energy Expenditure (TEE) is composed of three main factors, with a fourth considered in specific physiological states.
- Basal Energy Expenditure (BEE) or Resting Energy Expenditure (REE): Energy for basic functions at rest (breathing, circulation). Accounts for 60-70% of daily energy use.
- Thermic Effect of Food (TEF): Energy used for digestion and metabolism. About 10% of total energy intake.
- Energy Expended in Physical Activity (AEE): Energy used during movement. The most variable factor, ranging from 20-30%.
Additional energy is needed for growth, pregnancy, and lactation.
The Estimated Energy Requirement (EER) Calculation
The EER uses equations derived from research, like doubly labeled water studies, that accurately measure TEE. These equations incorporate key factors influencing energy expenditure:
- Age: Energy needs change throughout life.
- Sex: Males typically have higher EER due to larger size and more fat-free mass.
- Weight & Height: Larger individuals require more energy.
- Physical Activity Level (PAL): A coefficient reflecting activity level, the most variable factor in energy needs.
The PAL is categorized into four levels with specific coefficients:
- Sedentary (PA=1.0): Daily activities only.
- Low Active (PA=1.11-1.14): Daily activities plus 30-60 min moderate activity.
- Active (PA=1.25-1.27): Daily activities plus 60+ min moderate activity.
- Very Active (PA=1.45-1.54): Daily activities plus 60+ min moderate and 60+ min vigorous activity.
Energy Needs Across Different Life Stages
EER formulas are adjusted for specific life stages.
Children and Adolescents
Equations for this group account for age, sex, size, activity, and growth.
Pregnancy and Lactation
Pregnancy requires increased energy for fetal growth; the needed caloric increase varies by trimester. Lactation requires significantly more calories for milk production.
Older Adults
EER for older adults reflects the decline in metabolic rate and activity associated with age.
The Acceptable Macronutrient Distribution Range (AMDR)
Beyond total energy, DRIs include AMDR for macronutrients:
- Carbohydrates: 45-65% of calories.
- Fat: 20-35% of calories.
- Protein: 10-35% of calories for adults.
These ranges help reduce chronic disease risk and ensure essential nutrient intake.
DRI for Energy vs. Other DRIs
The EER differs from DRIs for other nutrients (vitamins/minerals), which include EAR, RDA, AI, and UL. Energy has no RDA or UL; energy balance is managed by monitoring body weight. Exceeding EER causes weight gain; falling below causes weight loss.
| Feature | DRI for Energy (EER) | DRIs for Micronutrients (RDA/AI/UL) |
|---|---|---|
| Primary Goal | Maintain energy balance (stable weight) based on individual factors. | Prevent nutrient deficiencies/excesses in populations. |
| Reference Values | Predictive equation based on age, sex, weight, height, PAL. | Specific numerical values (mg, mcg) for life stages. |
| Applicability | Personalized; requires weight monitoring to confirm accuracy. | General guidelines; assume needs follow a normal distribution. |
| Tolerable Upper Intake Level (UL) | Not applicable; excess causes weight gain, not toxicity. | Set for nutrients where excess causes adverse effects. |
Conclusion
The DRI estimation for energy, the Estimated Energy Requirement (EER), is a personalized guideline for energy balance. It's a predictive equation considering age, sex, height, weight, and Physical Activity Level. Using EER involves calculating the estimate and monitoring body weight for accuracy. This, with AMDRs for macronutrients, provides a framework for healthy dietary planning.
The History of EER
The EER equations were last updated in 2023 by the National Academies, building on 2005 work. These updates used newer science, including doubly labeled water studies, to be more inclusive of various populations, including those with overweight, obesity, and chronic diseases.
