Body weight calculations

• Assess body mass index (weight in kg/height in m²)

   ○ Underweight: < 18.5

   ○ Normal weight: 18.5–24.9

   ○ Overweight: 25–29.9

   ○ Obese: 30–39.5

   ○ Extremely obese: ≥ 40

• Assess actual body weight (ABW)

   ○ Normal: 90–120 % ideal body weight (IBW)

   ○ Mild malnutrition: 80–89 % IBW

   ○ Moderate malnutrition: 70–79 % IBW

   ○ Severe malnutrition: ≤ 69 % IBW

   ○ Overweight: > 120 % IBW

   ○ Obese: ≥ 150 % IBW

   ○ Extremely obese: ≥ 200 % IBW

• IBW

   ○ Male = 50 kg + (2.3 × number of inches over 5 ft)

   ○ Female = 45.5 kg + (2.3 × number of inches over 5 ft)

   ○ Use this weight for nutritional calculations in obese or extremely obese patients

• If ABW is less than IBW, use ABW

Assessing daily caloric and protein needs

• Predictive equations such as the Harris–Benedict equation may be utilized to estimate caloric needs (note: predictive equations should be used with caution, as they may provide a less accurate measure of energy requirements than indirect calorimetry; these equations may be even less predictive in the obese or extremely obese patients)

   ○ Males

     ■ (66 + 13.7 [wt in kg] + 5 [height in cm]—6.8 [age]) × AF × IF

   ○ Females

     ■ (655 + 9.6 [wt in kg] + 1.8 [height in cm]—4.7 [age]) × AF × IF

   ○ Activity factors (AF)

     ■ Out of bed: 1.3

     ■ Fever: 1.13

   ○ Injury factors (IF)

     ■ Infection: 1.2–1.8

     ■ Surgery: 1.2–1.8

     ■ Pancreatitis: 1–1.8

     ■ Burns or head trauma: up to 2

• Protein needs assessment

   ○ Usual: 0.8 g/kg/day

   ○ Renal failure: < 0.6 g/kg/day

   ○ Hemodialysis patients: 0.8–1.2 g/kg/day

   ○ Continuous renal replacement therapy: 1.2–1.5 g/kg/day

   ○ Liver failure: 0.5–1 g/kg/day

   ○ Critically ill patients: 1.2–2 g/kg/day

   ○ Burn patients: 2–3 g/kg/day

• Simple alternative to the Harris-Benedict or predictive equations

   ○ Maintenance or mild stress

     ■ Total calories: 20–25 kcal/kg

     ■ Nonprotein calories: 15–20 kcal/kg

     ■ Daily protein needs: 0.5–1 g/kg

   ○ Mild-to-moderate stress (minor infection, disease exacerbation)

     ■ Total calories: 25–30 kcal/kg

     ■ Nonprotein calories: 20–25 kcal/kg

     ■ Daily protein needs: 1–1.5 g/kg