Calculating Caloric Requirements in Obese Adolescents
For obese adolescents, use the Schofield equation based on actual body weight and height to calculate resting energy expenditure (REE), then multiply by an appropriate physical activity factor to determine total daily caloric needs. 1
Step-by-Step Calculation Algorithm
Step 1: Calculate Resting Energy Expenditure (REE)
Use the age- and sex-specific Schofield equations with actual body weight 1:
For ages 10-18 years:
For ages 3-10 years:
Step 2: Apply Physical Activity Factor (PAL)
Multiply the calculated REE by the appropriate activity level 1:
- Sedentary/hospitalized: PAL = 1.2-1.3 1
- Light activity: PAL = 1.5 1
- Moderate activity: PAL = 1.7 1
- Vigorous activity: PAL = 2.0 1
Step 3: Add Growth Allowance
Include additional calories for normal growth, which varies by developmental stage 1:
Total Energy Expenditure (TEE) = REE × PAL + growth allowance 1
Critical Considerations for Obese Adolescents
Use Actual Body Weight
Always use the adolescent's actual body weight in the Schofield equation, not ideal or adjusted weight. 1 The equations were developed using actual weight, and body weight is the main predictor of energy expenditure 1. This is particularly important because obese children and adolescents do not differ from normal-weight peers in energy expended for basal metabolism or physical activity tasks when body weight is considered 2.
When to Use Indirect Calorimetry
Measure REE using indirect calorimetry in obese adolescents with suspected metabolic alterations, severe complications, or when initial weight management approaches have been unsuccessful 1. The Schofield equation using both weight and height is least likely to underestimate REE compared to measured values and is therefore the preferred calculation method 1.
For Weight Maintenance vs. Weight Loss
For weight maintenance: Use the calculated TEE as the daily caloric target 1.
For weight loss: Subtract 500-750 kcal/day from the calculated TEE to achieve approximately 0.5 kg (1 pound) weight loss per week 1, 3. However, ensure intake never falls below 900 kcal/day minimum under medical supervision 1.
Common Pitfalls to Avoid
Do Not Use Adult Equations
The Harris-Benedict or Mifflin equations shown in the guidelines are designed for adults and should not be applied to adolescents 4. These adult formulas (REE = 10 × weight + 6.25 × height - 5 × age ± sex constant) do not account for the unique metabolic demands of growth and development in adolescents 4.
Avoid Separate Equations for Obese vs. Normal-Weight Youth
Do not use separate energy requirement equations based solely on weight classification 2. Research demonstrates that having two sets of equations is not theoretically justified, and using equations specifically for overweight/obese girls can inappropriately suggest higher energy intake, which is unwise for children already at risk 2.
Recognize the Energy Gap Phenomenon
Small daily energy imbalances of 110-165 kcal/day above maintenance needs are sufficient to cause gradual weight gain in children and adolescents 5, 6. This means that preventing weight gain requires only modest behavioral changes, such as eliminating one sugar-sweetened beverage (150 kcal) 5. However, obese adolescents who have already accumulated excess weight may have an energy imbalance ranging from 678-1017 kcal/day 5.
Account for Age-Related Patterns
Young obese children (under age 7 for girls, under age 10 for boys) report consuming significantly more calories than healthy-weight peers, while obese adolescents report consuming fewer calories 7. This suggests that increased energy intake in early childhood may relate to obesity onset, but other mechanisms like differences in energy expenditure contribute more to maintaining obesity through adolescence 7.
Expected Outcomes with Appropriate Caloric Management
With proper caloric restriction and comprehensive lifestyle intervention, expect BMI reduction of approximately 1.18 kg/m² over 6-12 months and weight loss of 3-4 kg over the intervention period 1. After initial weight loss, transition to a weight maintenance program focusing on normocaloric intake, continued physical activity, and ongoing behavioral support with family involvement 1.