Summary
Energy is required to sustain the body’s various functions, including respiration, circulation, physical work, and protein synthesis. This energy is derived from dietary carbohydrates, proteins, fats, and to a lesser extent, alcohol. Energy balance depends on an individual’s dietary energy intake and energy expenditure. The Dietary Reference Intake (DRI) value for energy is the Estimated Energy Requirement (EER), which is defined as the average dietary energy intake that is predicted to maintain energy balance in an adult of a defined age, sex, weight, height, level of physical activity, and life stage, consistent with maintaining health.
The DRIs for energy are used widely to provide guidance for maintaining energy balance on both an individual and group level. Applications include health care settings, support for federal nutrition policies such as the U.S. Dietary Guidelines for Americans and the Canadian Dietary Guidelines, and public feeding programs such as school meals. The DRIs for energy also serve as a critical data resource to support military nutrition standards and nutrition counseling and education programs.
The need to reexamine the DRIs for energy, last updated in 2005, stemmed from two key factors. First, both the U.S. and Canadian populations have experienced an imbalance in their energy intake and expenditure during the past several decades, such that weight status has trended toward overweight and obesity across demographic groups. Second, new scientific evidence has advanced knowledge about the energy intake and expenditure through the use of doubly labeled water (DLW) analysis.
This update of the DRIs for energy includes two major changes. First, the DRI population was considered relative to the health status of the U.S. and Canadian populations. To be more inclusive of those in the population who have or are at risk for chronic disease, the DRI population is now defined as the general population, including those with overweight, obesity, and chronic diseases, rather than the previous “generally healthy” population. Second, the data source for DLW was expanded to include databases that represent more diverse population groups.
STUDY TASK
The U.S. and Canadian governments asked the National Academies to convene an expert committee to examine the evidence and recommend updated EERs for their populations. Specifically, the committee was asked to assess the human requirements for energy intake and expenditure, and to consider age, sex, body size, body composition, level of physical activity, race/ethnicity, and other factors that may be warranted, based on the available data. Other significant variables for consideration included energy for growth and maturation for children, energy needs to support pregnancy, energy costs of milk production for lactating women, energy intake to achieve and maintain weight loss or weight gain, energy requirements to support recovery from disease and treatments or interventions such as surgery, and the health consequences of chronic overnutrition or undernutrition across the life span. The committee was asked to use data from studies that have incorporated DLW data, which are considered the benchmark standard to assess energy expenditure, to update the EER equations.
APPROACH TO THE TASK
The committee’s approach to gathering evidence published since the original DRIs for energy was to first conduct an umbrella review—a review of existing systematic reviews relevant to the questions in the statement of task. If no existing systematic reviews were found for topics that the committee considered to be of highest priority, the umbrella review was supplemented with relevant studies from the peer-reviewed published literature. This evidence-gathering approach differs from the two previous DRI updates, which included conducting new or updating existing systematic reviews prior to committee deliberations as the primary evidence base to support key committee deliberations, and from
the narrative review approach used in the original DRIs, which would not support the range or the quality of evidence the committee needed to carry out its task.
For its DLW data, the committee assembled a database comprising data obtained from the International Atomic Energy Agency (IAEA), the Institute of Medicine (IOM), the Hispanic Community Health Study of Latinos: Nutrition & Physical Activity Assessment Study (SOLNAS), and the Children’s Nutrition Research Center at the Baylor College of Medicine (CNRC). The committee’s database provided the following variables: total energy expenditure (TEE), age category, age, life stage, ethnicity, sex, body mass index (BMI), height, weight, basal metabolic rate (BMR) observed, BMR predicted, lactating, pregnant, gestational weeks, physical activity level (PAL) observed, PAL category observed, PAL predicted, PAL category predicted, fat-free mass (FFM), fat mass (FM), and FM percent.
EQUATIONS TO ESTIMATE TOTAL ENERGY EXPENDITURE
The committee engaged a consultant group to analyze the DLW data and generate prediction equations for TEE by age/sex and life-stage groups. In a weight-stable person, TEE is the most accurate measure of a person’s EER. The original EERs accounted for variability in physical activity by incorporating PAL, representing four categories as sedentary, low active, active, and very active as a variable (IOM, 2002/2005). The same PAL thresholds were used to define the categories across all life stages except infancy. However, recent evidence indicates that the physical activity level coefficient is not constant but varies significantly across age groups, particularly during the first 20 years of life, thus the previous PAL coefficients could not be used for all life stages. Therefore, an approach was developed to incorporate the age dependency into PAL categories for the development of the TEE prediction equations.
The committee used multiple methods to determine a PAL category (PALCAT). These methods by themselves could misclassify an individual, but taken together they provide a more thorough approach to capture the correct category. The PAL categories are inactive, low active, active, and very active. In the cases of pregnancy, lactation, and childhood (birth to 18 years of age), the committee also incorporated into the equations an allowance for growth, tissue accretion, and milk production in addition to TEE. The final TEE prediction equations used to derive the EERs are shown in Table S-1.
TABLE S-1 TEE Prediction Equations by Age/Sex and Life-Stage Group
| Men, 19 years and above | |
| Inactive | TEE = 753.07 – (10.83 × age) + (6.50 × height) + (14.10 × weight) |
| Low active | TEE = 581.47 – (10.83 × age) + (8.30 × height) + (14.94 × weight) |
| Active | TEE = 1,004.82 – (10.83 × age) + (6.52 × height) + (15.91 × weight) |
| Very active | TEE = – 517.88 – (10.83 × age) + (15.61 × height) + (19.11 × weight) |
| NOTE: R2 = 0.73; R2 adj = 0.73; R2 shr = 0.73; RMSE = 339 kcal/d; MAPE = 9.4%; MAE = 266 kcal/d. | |
| Women, 19 years and above | |
| Inactive | TEE = 584.90 – (7.01 × age) + (5.72 × height) + (11.71 × weight) |
| Low active | TEE = 575.77 – (7.01 × age) + (6.60 × height) + (12.14 × weight) |
| Active | TEE = 710.25 – (7.01 × age) + (6.54 × height) + (12.34 × weight) |
| Very active | TEE = 511.83 – (7.01 × age) + (9.07 × height) + (12.56 × weight) |
| NOTE: R2 = 0.71; R2 adj = 0.70; R2 shr = 0.70; RMSE = 246 kcal/d; MAPE = 8.7%; MAE = 191 kcal/d. | |
| Boys, 3–18 years | |
| Inactive | TEE = – 447.51 + (3.68 × age) + (13.01 × height) + (13.15 × weight) |
| Low active | TEE = 19.12 + (3.68 × age) + (8.62 × height) + (20.28 × weight) |
| Active | TEE = – 388.19 + (3.68 × age) + (12.66 × height) + (20.46 × weight) |
| Very active | TEE = – 671.75 + (3.68 × age) + (15.38 × height) + (23.25 × weight) |
| NOTE: R2 = 0.92; R2 adj = 0.92; R2 shr = 0.92; RMSE = 259 kcal/d; MAPE = 7.1%; MAE = 163 kcal/d. | |
| Girls, 3–18 years | |
| Inactive | TEE = 55.59 – (22.25 × age) + (8.43 × height) + (17.07 × weight) |
| Low active | TEE = – 297.54 – (22.25 × age) + (12.77 × height) + (14.73 × weight) |
| Active | TEE = – 189.55 – (22.25 × age) + (11.74 × height) + (18.34 × weight) |
| Very active | TEE = – 709.59 – (22.25 × age) + (18.22 × height) + (14.25 × weight) |
| NOTE: R2 = 0.84; R2 adj = 0.84; R2 shr = 0.83; RMSE = 237 kcal/d; MAPE = 8.2%; MAE = 165 kcal/d. | |
| Boys, 0–2 years | |
| TEE = –716.45 – (1.00 × age) + (17.82 × height) + (15.06 × weight) | |
| NOTE: R2 = 0.83; R2 adj = 0.83; R2 shr = 0.83; RMSE = 104 kcal/d; MAPE = 13.6%; MAE = 79 kcal/d | |
| Girls, 0–2 years | |
| TEE = –69.15 + (80.0 × age) + (2.65 × height) + (54.15 × weight) | |
| NOTE: R2 = 0.83; R2 adj = 0.83; R2 shr = 0.83; RMSE = 95 kcal/d; MAPE = 12.8%; MAE = 74 kcal/d. | |
| Pregnant women in their second and third trimester of pregnancy | |
| Inactive | TEE = 1,131.20 – (2.04 × age) + (0.34 × height) + (12.15 × weight) + (9.16 × gestation) |
| Low active | TEE = 693.35 – (2.04 × age) + (5.73 × height) + (10.20 × weight) + (9.16 × gestation) |
| Active | TEE = – 223.84 – (2.04 × age) + (13.23 × height) + (8.15 × weight) + (9.16 × gestation) |
| Very active | TEE = – 779.72 – (2.04 × age) + (18.45 × height) + (8.73 × weight) + (9.16 × gestation) |
| NOTE: R2 = 0.63; R2 adj = 0.62; R2 shr = 0.61; RMSE = 282 kcal/d; MAPE = 8.8%; MAE = 222 kcal/d. | |
NOTES: TEE = total energy expenditure; kcal/d = kilocalorie per day; TEE is in kilocalories/day, age is in years, weight is in kilograms, height is in centimeters, and gestation is in weeks. R2 = R squared; R2 adj = adjusted R squared; R2 shr = shrunken R squared; RMSE = root mean squared error; MAPE = mean absolute percentage error; MAE = mean absolute error. RMSE is the same as standard error of the estimate (SEE).
EQUATIONS TO ESTIMATE ENERGY REQUIREMENTS
The EER is used to predict an appropriate energy intake to plan and assess diets for individuals and groups. The EER equations represent the committee’s estimates of energy requirements by age/sex, physical activity, and life-stage group. The committee used the TEE equations to develop EER equations by age/sex and life-stage groups for the United States and Canada. The EER equations are shown in Tables S-2 through S-6.
TABLE S-2 Summary Table of EER Equations by Age, Sex, Physical Activity, and Energy Cost of Growth: Children and Adolescents
| Age Group | Sex | PAL Category | EER Equation (kcal/d) |
|---|---|---|---|
| 0 to 2.99 months | M | — | EER = –716.45 – (1.00 × age) + (17.82 × height) + (15.06 × weight) + 200 |
| F | — | EER = –69.15 + (80.0 × age) + (2.65 × height) + (54.15 × weight) + 180 | |
| 3 to 5.99 months | M | — | EER = –716.45 – (1.00 × age) + (17.82 × height) + (15.06 × weight) + 50 |
| F | — | EER = –69.15 + (80.0 × age) + (2.65 × height) + (54.15 × weight) + 60 | |
| 6 months to 2.99 years | M | — | EER = –716.45 – (1.00 × age) + (17.82 × height) + (15.06 × weight) + 20 |
| F | — | EER = –69.15 + (80.0 × age) + (2.65 × height) + (54.15 × weight) + 20/15a | |
| 3 to 13.99 years | M | Inactive | EER = –447.51 + (3.68 × age) + (13.01 × height) + (13.15 × weight) + 20/15/25b |
| Low active | EER = 19.12 + (3.68 × age) + (8.62 × height) + (20.28 × weight) + 20/15/25 | ||
| Active | EER = –388.19 + (3.68 × age) + (12.66 × height) + (20.46 × weight) + 20/15/25 | ||
| Very active | EER = –671.75 + (3.68 × age) + (15.38 × height) + (23.25 × weight) + 20/15/25 | ||
| F | Inactive | EER = 55.59 – (22.25 × age) + (8.43 × height) + (17.07 × weight) + 15/30c | |
| Low active | EER = –297.54 – (22.25 × age) + (12.77 × height) + (14.73 × weight) + 15/30 | ||
| Active | EER = –189.55 – (22.25 × age) + (11.74 × height) + (18.34 × weight) + 15/30 | ||
| Very active | EER = –709.59 – (22.25 × age) + (18.22 × height) + (14.25 × weight) + 15/30 |
| Age Group | Sex | PAL Category | EER Equation (kcal/d) |
|---|---|---|---|
| 14 to 18.99 years | M | Inactive | EER = –447.51 + (3.68 × age) + (13.01 × height) + (13.15 × weight) + 20 |
| Low active | EER = 19.12 + (3.68 × age) + (8.62 × height) + (20.28 × weight) + 20 | ||
| Active | EER = –388.19 + (3.68 × age) + (12.66 × height) + (20.46 × weight) + 20 | ||
| Very active | EER = –671.75 + (3.68 × age) + (15.38 × height) + (23.25 × weight) + 20 | ||
| F | Inactive | EER = 55.59 – (22.25 × age) + (8.43 × height) + (17.07 × weight) + 20 | |
| Low active | EER = –297.54 – (22.25 × age) + (12.77 × height) + (14.73 × weight) + 20 | ||
| Active | EER = –189.55 – (22.25 × age) + (11.74 × height) + (18.34 × weight) + 20 | ||
| Very active | EER = –709.59 – (22.25 × age) + (18.22 × height) + (14.25 × weight) + 20 |
NOTES: kcal/d = kilocalories per day; PAL = physical activity level; EER = Estimated Energy Requirement. Age is in years, weight is in kilograms, and height is in centimeters.
a Energy cost of growth for girls: 6 to 11.99 months: 20 kcal/d; 12 to 35.99 months: 15 kcal/d.
b Energy cost of growth for boys: 3 y: 20 kcal/d; 4 to 8 y: 15 kcal/d; 9 to 13 y: 25 kcal/d.
c Energy cost of growth for girls: 3 y: 15 kcal/d; 4 to 8 y: 15 kcal/d; 9 to 13 y: 30 kcal/d.
TABLE S-3 Summary Table of EER Equations Based on TEE Prediction by Age, Sex, and Physical Activity: Adults
| Age Group | Sex | PAL Category | EER Equation (kcal/d) |
|---|---|---|---|
| 19+ years | M | Inactive | EER = 753.07 – (10.83 × age) + (6.50 × height) + (14.10 × weight) |
| Low active | EER = 581.47 – (10.83 × age) + (8.30 × height) + (14.94 × weight) | ||
| Active | EER = 1,004.82 – (10.83 × age) + (6.52 × height) + (15.91 × weight) | ||
| Very active | EER = –517.88 – (10.83 × age) + (15.61 × height) + (19.11 × weight) | ||
| F | Inactive | EER = 584.90 – (7.01 × age) + (5.72 × height) + (11.71 × weight) | |
| Low active | EER = 575.77 – (7.01 × age) + (6.60 × height) + (12.14 × weight) |
| Age Group | Sex | PAL Category | EER Equation (kcal/d) |
|---|---|---|---|
| Active | EER = 710.25 – (7.01 × age) + (6.54 × height) + (12.34 × weight) | ||
| Very active | EER = 511.83 – (7.01 × age) + (9.07 × height) + (12.56 × weight) |
NOTES: kcal/d = kilocalories per day; PAL = physical activity level; EER = Estimated Energy Requirement; TEE = total energy expenditure. For weight stable adults, EER (kcal/d) = TEE (kcal/d). Age is in years, weight is in kilograms, and height is in centimeters.
TABLE S-4 Summary Table of EER Equations for Pregnant Women During the Second and Third Trimesters of Pregnancy
| Life Stage | PAL Category | EER Equation (kcal/day) |
|---|---|---|
| 2nd and 3rd trimester of pregnancya | Inactive | EER = 1,131.20 – (2.04 × age) + (0.34 × height) + (12.15 × weight) + (9.16 × gestation) + energy deposition |
| Low active | EER = 693.35 – (2.04 × age) + (5.73 × height) + (10.20 × weight) + (9.16 × gestation) + energy deposition | |
| Active | EER = –223.84 – (2.04 × age) + (13.23 × height) + (8.15 × weight) + (9.16 × gestation) + energy deposition | |
| Very active | EER = –779.72 – (2.04 × age) + (18.45 × height) + (8.73 × weight) + (9.16 × gestation) + energy deposition |
NOTES: For pregnancy: EER (kcal/d) = TEE (kcal/d) + energy deposition (kcal/d). Energy deposition/mobilization (kcal/d) estimated for underweight (UW), normal weight (NW), overweight (OW), and obese (OB) pregnant women during the 2nd and 3rd trimesters of pregnancy: + 300 kcal/d for UW; + 200 kcal/d for NW; + 150 kcal/d for OW; –50 kcal/d for OB. EERs are in kilocalories/day, age is in years, height is in centimeters, weight is in kilograms, gestation is in weeks, energy deposition is in kilocalories/day.
a For the 1st trimester of pregnancy, the nonpregnant TEE prediction equation should be used. It is assumed that energy deposition/mobilization is negligible and is therefore ignored.
TABLE S-5 Summary Table of EER Equations for Women and Girls Exclusively Breastfeeding 0 to 6 Months Postpartum
| Age Group | PAL Category | EER Equation (kcal/day) |
|---|---|---|
| Women, 19 years and above | Inactive | EER = 584.90 – (7.01 × age) + (5.72 × height) + (11.71 × weight) + energy cost of milk production – energy mobilization |
| Low active | EER = 575.77 – (7.01 × age) + (6.60 × height) + (12.14 × weight) + energy cost of milk production – energy mobilization | |
| Active | EER = 710.25 – (7.01 × age) + (6.54 × height) + (12.34 × weight) + energy cost of milk production – energy mobilization | |
| Very active | EER = 511.83 – (7.01 × age) + (9.07 × height) + (12.56 × weight) + energy cost of milk production – energy mobilization | |
| Girls, < 19 years | Inactive | EER = 55.59 – (22.25 × age) + (8.43 × height) + (17.07 × weight) + energy cost of milk production – energy mobilization |
| Low active | EER = –297.54 – (22.25 × age) + (12.77 × height) + (14.73 × weight) + energy cost of milk production – energy mobilization | |
| Active | EER = –189.55 – (22.25 × age) + (11.74 × height) + (18.34 × weight) + energy cost of milk production – energy mobilization | |
| Very active | EER = –709.59 – (22.25 × age) + (18.22 × height) + (14.25 × weight) + energy cost of milk production – energy mobilization |
NOTES: For exclusively breastfeeding 0 to 6 months postpartum: EER (kcal/d) = TEE (kcal/d) + energy cost of milk production (kcal/d) – energy mobilization (kcal/d). Energy cost of milk production estimated for women and girls exclusively breastfeeding 0 to 6 months postpartum: 540 kcal/d. Energy mobilization estimated for women and girls exclusively breastfeeding 0 to 6 months postpartum: 140 kcal/d. EERs are in kilocalories/day, age is in years, height is in centimeters, weight is in kilograms, energy cost of milk production is in kilocalories/day, and energy mobilization is in kilocalories/day.
TABLE S-6 Summary Table of EER Equations for Women and Girls Partially Breastfeeding 7 to 12 Months Postpartum
| Age Group | PAL Category | EER Equation (kcal/day) |
|---|---|---|
| Women, 19 years and above | Inactive | EER = 584.90 – (7.01 × age) + (5.72 × height) + (11.71 × weight) + energy cost of milk production |
| Low active | EER = 575.77 – (7.01 × age) + (6.60 × height) + (12.14 × weight) + energy cost of milk production | |
| Active | EER = 710.25 – (7.01 × age) + (6.54 × height) + (12.34 × weight) + energy cost of milk production | |
| Very active | EER = 511.83 – (7.01 × age) + (9.07 × height) + (12.56 × weight) + energy cost of milk production | |
| Girls, < 19 years | Inactive | EER = 55.59 – (22.25 × age) + (8.43 × height) + (17.07 × weight) + energy cost of milk production |
| Low active | EER = –297.54 – (22.25 × age) + (12.77 × height) + (14.73 × weight) + energy cost of milk production | |
| Active | EER = –189.55 – (22.25 × age) + (11.74 × height) + (18.34 × weight) + energy cost of milk production | |
| Very active | EER = –709.59 – (22.25 × age) + (18.22 × height) + (14.25 × weight) + energy cost of milk production |
NOTES: For partially breastfeeding 7 to 12 months postpartum: EER (kcal/d) = TEE (kcal/d) + energy cost of milk production (kcal/d). Energy cost of milk production estimated for women and girls partially breastfeeding 7 to 12 months postpartum: 380 kcal/d. EERs are in kilocalories/day, age is in years, height is in centimeters, weight is in kilograms, and energy cost of milk production is in kilocalories/day.
ASSESSMENT OF ENERGY INTAKE AND EXPENDITURE AND OUTCOME MEASURES
Part of the committee’s task was to consider the methods used to determine energy intake and expenditure and outcome measures. The committee began by identifying reference data that could be used to show EERs among various age/sex and life-stage groups. The committee also sought data that could be used to assess energy status, expressed as prevalence of underweight, normal weight, overweight, and obesity, among various age/sex/ethnic groups in the United States and Canada. These data included other measures of body weight and energy status that are linked with health risk, such as waist circumference and dual-energy x-ray absorptiometry (DXA) measures. The committee’s findings confirm the high levels of overweight and obesity in both the child and adult populations of the United States and Canada.
The committee further evaluated dietary intake data from U.S. and Canadian national surveys and compared results to the estimated EERs. This involved comparing peer-reviewed literature on reported energy intakes based on 24-hour dietary recalls with objective DLW measures, which showed that DLW was a more accurate measure. This illustrated why assessing reported energy intake is not an appropriate method for determining actual energy intake at the population level. Lastly, the committee reviewed current evidence on the influence of BMI on energy expenditure.
APPLICATIONS OF THE ESTIMATED ENERGY REQUIREMENTS TO DIETARY PLANNING AND ASSESSMENT
The DRIs, including the EER, have primary applications in the planning and assessment of dietary intakes for both individuals and groups, with the overarching goal of achieving intakes that are adequate but not excessive. In contrast to other DRIs, for energy a “safe range of intake” does not apply because intakes above or below requirements lead to either weight gain or loss. Therefore, energy has neither a Recommended Dietary Allowance (RDA) nor a Tolerable Upper Intake Level (UL); rather, the EER equation is used to predict an appropriate energy intake for individuals and groups.
Planning for energy intakes using the EER is a two-step process. The first step is to select the appropriate EER equation to use for the individual or group and calculate the EER, and the second step is to monitor body weight over time—if undesired weight gain or loss occur, adjust the energy intake as needed to maintain the desired weight. A critical element in selecting the appropriate EER equation is identifying the correct PAL category: inactive, low active, active, or very active.
Planning Energy Intakes for Individuals
The EER for an individual is calculated by inserting the person’s age, height, and weight into the appropriate EER equation. For example, the EER for a 22-year-old woman who is 165 cm in height, weighs 63 kg, and was determined to have a low active PAL is calculated as follows:
In this example, the calculated EER represents the average requirement of women with these values for age, height, weight, and PAL category. Like other nutrients, however, requirements for energy vary among individuals with the same age, height, weight, and PAL category. The extent of variability is indicated by the standard error of the predicted value (SEPV), which reflects how much an individual’s requirement may vary from the value predicted by the EER equation. Assuming that this variation is normally distributed, approximately 68 percent of individuals with given characteristics will have an energy requirement within 1 SEPV of the value predicted by the EER equation and almost everyone with those characteristics will have energy requirements within 1.96 SEPV of the value predicted by the equation.
When calculating the EER for the second and third trimesters of pregnancy, a woman’s prepregnant BMI and the number of weeks she has been pregnant is needed, along with her current age, height, weight, and PAL category. The EER equation also includes an increment, which varies depending on a woman’s prepregnant BMI, for the deposition of new tissue necessary to support the products of conception. Another update to the EER equation was to ensure that, if physical activity changes during pregnancy, the EER will be adjusted to reflect the change. Thus, the appropriate EER equation for pregnancy is based on the woman’s current PAL, age, height, weight, and weeks of pregnancy and includes extra calories needed for energy deposition during the second and third trimesters.
To plan for energy intake during lactation, the EER equation for an appropriate PAL category for women 19 years of age and older is used, to which an increment is added. The increments are based on the energy cost of producing milk and energy mobilized among women who are exclusively breastfeeding during the first 6 months of lactation and then only the cost of producing milk for partially breastfeeding beyond 6 months. This additional energy cost assumes a gradual weight loss of 0.64 kg/month in the first 6 months postpartum.
During pregnancy, monitoring weight gain is crucial; energy intake can be adjusted as needed to achieve the appropriate rate and amount of weight gain throughout pregnancy to avoid adverse outcomes for the mother or child. It is also important to monitor the rate of weight loss for the postpartum woman and adjust energy intake as needed or desired to facilitate a quicker return to prepregnancy weight.
Planning Energy Intakes for Groups
Planning energy intake levels for groups is challenging, as group members may vary considerably in terms of age, sex, body size, and physical activity level, and planners may or may not have access to
the individual characteristics of group members. As with individuals, the planning process includes selecting the appropriate EER equation, followed by monitoring body weight over time and adjusting the energy content of the food provided as needed. The first step in planning for groups differs from that for individuals in that a reference individual is identified based on median heights and weights of the group members (or if data for group members are not available, based on median height and weight of the appropriate age/sex group among the overall population). Alternatively, if the planner knows that most of the group members are in a specific weight category, EERs may be calculated using reference heights and weights for those in a specific weight category, such as normal weight, overweight, or obese.
The committee identified a number of limitations in the approach to planning energy intakes of groups. While the EER will closely approximate the average energy requirements of the group, it will overestimate or underestimate the requirements of many group members. The consequences differ depending on the extent to which individual group members can choose the amounts of food they receive or whether everyone in the group receives an identical amount of food and whether the planner provides all or just some meals and snacks throughout the day. The risk of weight loss in group members with above-average energy requirements is greatest when everyone receives the same amount of food and the planner provides all meals and snacks; while those with lower-than-average energy requirements may choose not to eat all the food they are served.
Assessing Energy Intakes for Individuals
The calculated EER for an individual has a large confidence interval, so comparing an individual’s energy intake to their calculated EER does not indicate whether they are meeting, exceeding, or falling below their actual energy requirement. Overreporting and underreporting occur among most age/sex groups, with underreporting being the most frequent occurrence, the extent of which appears to vary by factors such as age, sex, body weight, and health status. Thus, assessing adequacy of energy intake based on self-reported dietary intake data is not considered accurate. The biological indicator of adequacy for energy (body weight maintenance) is easily measured, however, without need of laboratory assessments. By definition, nongrowing individuals maintaining a stable weight are meeting their energy requirements, while those currently gaining or losing weight are exceeding or falling below their requirements, respectively. For growing children and pregnant women, meeting the energy requirement is reflected by gaining the expected amount of weight over time. Inadequate or excessive intakes in these groups are reflected by
failure to gain the expected amount of weight (or in some cases, by weight loss) or gaining excessive amounts of weight, respectively.
Assessing Energy Intakes for Groups
As with individuals, it is not appropriate to use reported energy intake to determine the prevalence of energy inadequacy or excess in a group. For many nutrients, prevalence of inadequacy in a group is estimated by determining the proportion of the group’s usual nutrient intake distribution that falls below the Estimated Average Requirement (EAR) (IOM, 2000), but this cannot be done for energy because intakes are highly correlated with requirement and misreporting is prevalent.
Reported energy intakes from national surveys indicate that intakes are generally well below the EER calculated for the group for adults. Further, they are not subdivided by PAL category, as the surveys do not collect data that would permit a PAL category to be determined. Nevertheless, in all cases, the reported median energy intakes were well below the EER. Additionally, the gap between reported intakes and the EER for inactive PAL increased across BMI categories. Systematic misreporting of energy intakes underlies the differences between reported intakes of groups and the EER for the group. Rather than relying on reported energy intakes, the adequacy of a group’s energy intake is better determined by assessing its relative weight status.
RISK CHARACTERIZATION AND PUBLIC HEALTH IMPLICATIONS
The committee examined evidence gathered through its umbrella review to assess the relevance, strengths, and limitations for elucidating relationships between a given determinant and a health outcome. Three measures were used as indicators of intake deviations from energy requirements: (1) the association with BMI, (2) the association with weight change, and (3) the association with weight cycling.
Chronic Disease Risk for Overweight and Obesity
Although risk for some chronic disease states may be better predicted by waist circumference, waist–hip ratio, or waist–height ratio, the body of evidence reviewed by the committee indicates a strong relationship between high BMI and functional disabilities, impaired quality of life, serious disease states, and mortality.
Weight Change
Systematic reviews of longitudinal studies examining the association between weight change and chronic disease as well as mortality provided limited evidence of significance for a causal effect of weight change on disease risk and mortality. In one systematic review, weight change measured from childhood to adulthood that included a shift of normal to high weight or excessive weight in both time periods was associated with higher risks of incident cardiovascular disease and hypertension. Evidence for an association of weight change with diabetes is more consistent. Length of follow-up, elimination of preexisting conditions, and whether weight is measured are critical issues to reconcile in this body of literature.
Weight Cycling
Twenty to 55 percent of adults with overweight or obesity have a history of weight cycling, a common outcome among individuals seeking weight loss treatment. The range of consequences of weight cycling on health outcomes, however, have yet to be clarified. Repeated cycles of weight loss and regain have been shown to promote greater subsequent or future weight gain, and this has been hypothesized to occur through the process of adaptive thermogenesis or energy compensation and thus may predispose an individual to greater risk of obesity or increased adiposity as a consequence. Long-term obesity is a concern because of public health implications such as predisposition to risk of numerous chronic disease outcomes.
RESEARCH RECOMMENDATIONS
Factors Affecting Energy Requirements
Data are limited on how variables such as the macronutrient composition of the diet, the gut microbiome, dietary fiber, and genetic factors affect energy requirements at all life stages. This information would be particularly valuable for individuals participating in DLW studies.
To better determine the EER for pregnant women, there is a need for more DLW data and body composition data on pregnant women across all prepregnancy BMI categories. These data could be analyzed specifically to identify the energy needs for pregnant women who have gained within and those who have gained outside the IOM and NRC (2009) gestational weight gain recommendations.
Research Recommendation 1
The committee recommends that the National Institutes of Health (NIH), the U.S. Department of Agriculture (USDA), the Centers for Disease Control and Prevention (CDC), the Department of Veterans Affairs (VA), and Health Canada commit funding to nutrition and kinesiology research that would inform future updates of the Dietary Reference Intakes (DRIs) for energy in all sex and life-stage groups. The committee further recommends research on methodologies to individualize energy requirements when providing precision nutrition care.
Energy Metabolism in Special Population Groups
Energy metabolism data are sparse for diverse racial/ethnic groups, including indigenous populations in the United States and Canada. Evidence on factors that affect energy metabolism and energy requirements in diverse populations is also lacking. Further, the effect of sarcopenic obesity on energy requirements is not well understood, nor is energy balance, energy expenditure, and energy compensation in individuals with BMI ≥ 50. Additionally, data from DLW studies are lacking for certain life-stage groups, and at various BMI levels.
Given the increasing prevalence of chronic disease and other diet-related risk factors across the U.S. and Canadian populations, evidence is needed on medications that affect energy metabolism, and on how medications and procedures such as bariatric surgery affect energy metabolism, especially TEE.
Research Recommendation 2
The committee recommends that NIH, USDA, CDC, VA, and Health Canada commit funding to nutrition research that would inform future updates of the DRIs in diverse populations, including infants, children, adolescents, the oldest old, lactating women, individuals taking medications, and individuals at higher body mass index (BMI) levels.
Weight Change and Energy Metabolism
There is insufficient evidence on defining a weight cycle and determining what frequency, amount, and duration of cycling indicates a significant effect on energy metabolism. In addition, reporting on how weight change is measured is inconsistent, and information on population
characteristics and research methodologies relating to the measurement of body weight are inadequately reported in many research articles.
Research Recommendation 3
The committee recommends that investigators studying energy balance and national health surveillance monitoring provide participants’ rationales for weight gain or weight loss. In addition, published research reports should indicate whether weight change was measured or self-reported. Nutrition and kinesiology researchers should also use accepted definitions that differentiate basal and resting metabolic rate to standardize terminology in reporting study findings.
Research Recommendation 4
The committee further recommends that research agencies develop a checklist of quality factors (to guide study designs and protocols, and to evaluate study quality) that are relevant to evaluating energy intake imbalances and to relating intake imbalances to health outcomes. Journal editors should require documentation from authors to show that articles accepted for publication have met quality factors for assessing energy intake imbalances.
Application of the EER to Individuals and Population Groups
To support the application of this report’s recommendations and their translation to population-level survey data, research is needed on the relationship between TEE and PAL categories using metrics that define physical activity intensity and duration. Because of the complexity in factors associated with selecting a PAL category and calculating the EER, there is potential for error in calculation of the EER owing to misclassification.
Research Recommendation 5
The committee recommends that USDA, the U.S. Food and Drug Administration, NIH, and Health Canada commit funding to develop an app to facilitate calculations of EERs for specific life-stage groups to ensure the wide dissemination and appropriate application of the new EERs. Additionally, CDC
and Canada’s Health Statistics agencies should incorporate into their national health surveys measures of physical activity that are compatible with the physical activity level (PAL) categories needed to calculate EERs. Those U.S. and Canadian agencies that fund research to support public health initiatives should invest in development and validation of measures of physical activity that can be used in public health and research contexts.
REFERENCES
IOM (Institute of Medicine). 2000. Dietary Reference Intakes: Applications in dietary assessment. Washington, DC: National Academy Press. https://doi.org/10.17226/9956.
IOM. 2002/2005. Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, DC: The National Academies Press.
IOM and NRC (National Research Council). 2009. Weight gain during pregnancy: Reexamining the guidelines. Washington, DC: The National Academies Press.
