1. Controversies in the determination of energy requirements
Dr. Elizabeth Weekes
Department of Nutrition & Dietetics
Guy’s & St. Thomas’ Hospitals NHS Foundation Trust
London

3. Controversies
Is measured energy expenditure (MEE) always the most accurate way to determine energy requirements?
Is it valid to extrapolate results from a study population to an individual patient?
What should we do in clinical practice?
If I feed my patient to estimated energy requirements will he/she do better than if I don’t?

4. Total Energy Expenditure
Activity
BMR

5. Methods of estimating energy expenditure
Indirect calorimetry
Short-term measurements (up to 24 hours)
Hood/ventilator modes
Doubly-labelled water technique
Long-term measurements (several weeks)
Cost and technical considerations
Measures Total Energy Expenditure
Prediction equations + fudge factors

6. Prediction equations
May over or under-estimate compared with measured energy expenditure (MEE)
Inadequately validated
Poor predictive value for individuals
Open to misinterpretation
(Cortes & Nelson, 1989; Malone, 2002; Reeves & Capra, 2003)

7. Basal metabolic rate Minimal intra-individual variation ~ 3%
Inter-individual variation ~ 10% depending on:-
proportions of body cell mass and metabolically active organs and tissues
thyroid function
circadian rythms

8. Conditions essential for measuring BMR
Post-absorptive (12 hour fast)
Lying still at physical and mental rest
Thermo-neutral environment (27 – 29oC)
No tea/coffee/nicotine in previous 12 hours
No heavy physical activity previous day
Gases must be calibrated
Establish steady-state (~ 30 minutes)
* If any of the above conditions are not met =
Resting Energy Expenditure (REE)

9. Measured Energy Expenditure (MEE)
Measured in clinical setting by indirect calorimetry
(rarely available in UK hospitals)
Recommended in certain conditions e.g. liver disease, obesity, critical illness (ASPEN, 2002)
Needs to be measured correctly in order to provide valid and reliable data

10. MEE in healthy subjects
Activity
DIT
Doubly-labelled
water
BMR
Indirect
calorimetry

11. MEE in clinical studies
Calibration
How long and how often to measure
Achieving a steady-state
Lying in bed, awake and aware
No social or physical interactions
Avoid haemodialysis and filtration
Patient/apparatus interface
Hood/canopy
Ventilated patients

12. MEE in disease
Activity
DIT
BMR +
Stress
Indirect
calorimetry

13. Controversies
Is measured energy expenditure (MEE) always the most accurate way to determine energy requirements?
Is it valid to extrapolate results from a study population to an individual patient?
What should we do in clinical practice?
If I feed my patient to estimated energy requirements will he/she do better than if I don’t?

14. Reviewing the literature
Patient demography
Sample size
Diagnosis
Severity of illness/injury and metabolic status
Nutritional status
Nutritional intake
Temperature (room and patient)
Therapeutic interventions e.g. ventilation, drugs
Methodology

15. Energy requirements in COPD
Schols et al. (1996)
Age 61 (+ 6) years; BMI 23.5 (+ 4.2) kg/m2
REE < 105 % HB in 14 patients
REE > 120 % HB in 16 patients (weight-losing,  FFM,  CRP and  acute phase proteins)
30 stable COPD patients admitted to rehabilitation unit
Vermeeren et al., (1997)
Age 63 (+ 8) years; BMI 23.0 (+ 3.2) kg/m2
REE 123 (+ 11) % HB on admission
REE 113 (+ 14) % HB on discharge
(REE > 110 % HB in 10 patients at discharge)
23 acute COPD patients admitted to hospital

16. Controversies
Is measured energy expenditure (MEE) always the most accurate way to determine energy requirements?
Is it valid to extrapolate results from a study population to an individual patient?
What should we do in clinical practice?
If I feed my patient to estimated energy requirements will he/she do better than if I don’t?

17. Estimating requirements in clinical practice (I)
Assess metabolic state
Is my patient metabolically stressed, recovering or anabolic
Is there a risk of re-feeding syndrome?
Establish physical activity level
Is the patient sedated, bed-bound, mobile on ward, receiving physiotherapy, at home
Determine goals of treatment
e.g. minimise losses, weight maintenance or weight change

19. Metabolic response to injury

20. Assessing metabolic stress
Stressed
 temperature
 urea
 white cell count
 C-reactive protein
 albumin
 insulin resistance
Oedema
N.B. Stress response may be blunted in immuno- compromised and elderly patients

21. Stress factors Timing of measurements
Over (hyperalimentation) vs. under-feeding
Changes in therapeutic interventions
e.g. improved wound care, anti-pyretics, sedation, control of ambient room temperature
 Err towards lower end of the range and monitor

22. Estimating requirements in clinical practice (I)
Assess metabolic state
Is my patient metabolically stressed, recovering or anabolic
Is there a risk of re-feeding syndrome?
Establish physical activity level
Is the patient sedated, bed-bound, mobile on ward, receiving physiotherapy, at home
Determine goals of treatment
e.g. minimise losses, weight maintenance or weight change

23. Physical activity Assumes normal neuro-muscular function
Review literature for patients with abnormal function
e.g. brain injury, Parkinson’s disease, cerebral palsy, motor neurone disease and Huntington’s chorea
Prolonged and active physiotherapy
Increased effort of moving injured/painful limbs
Mechanical inefficiency e.g. COPD (Baarends et al., 1997)

25. Physical activity
Free living individuals have higher energy expenditure due to physical activity
Nursing home and house-bound patients may have similar activity levels to hospitalised patients
For active patients in the community a PAL should be added

26. Estimating requirements in clinical practice (I)
Assess metabolic state
Is my patient metabolically stressed, recovering or anabolic
Is there a risk of re-feeding syndrome?
Establish physical activity level
Is the patient sedated, bed-bound, mobile on ward, receiving physiotherapy, at home
Determine goals of treatment
Should I aim to minimise losses, maintain weight or achieve weight change (loss or gain)

27. Estimating requirements in clinical practice II
Be aware of the literature on energy requirements in your patient group (and any gaps in the evidence)
Compare your patient with available literature and either assign relevant stress factor OR adjust for weight change
Monitor, review and amend requirements as clinical condition, physical activity and nutritional goals change

28. If I feed my patient to estimated energy requirements will he/she do better than if I don’t?
Over-feeding is not good
(Askanazi et al., 1980; Lowry & Brenman, 1979; Kirkpatrick et al., 1981)
Is under-feeding always bad?
Should we start everyone on 1500 kcal/day?

29. Conclusions Estimated requirements are only a starting point
Set realistic goals of treatment for each patient
Monitor and amend as patient’s condition changes
Review and critically appraise the literature
Be aware of gaps in the evidence
Understand the limitations of guidelines
Check applicability to your patients
Contribute to research and audit projects