Patients with kidney disease need accurate advice on their diet. Researchers know very little about energy needs and nutritional requirements in kidney patients. Simple tools are needed to calculate calorie requirements so that good bed-side advice can be given to patients, and to allow cost-effective research. This study aimed to measur energy requirements in kidney disease using a gold-standard safe and very accurate method called the "doubly labelled water technique". The study has compared measurements with less costly measurements obtained using a device which measures oxygen content of air breathed out. The study has also measured physical activity levels with questionnaires.

Background The function of the kidneys is to remove waste products of metabolism, and despite advances in treatment of CKD little is known about metabolic rate in renal disease. Increased knowledge about metabolic rate would have numerous potential benefits.

Little is known of the effects of metabolic rate on kidney disease. This study was designed to define the relationship of metabolic rate with degree of kidney function.

Study design and methods In an observational cohort study, the investigators studied Total Energy Expenditure in 80 patients with CKD stage 1-5 using the doubly-labelled water technique over a 14 day period. The group was divided such that half had stage 1-3 CKD and half stage 4-5. All subjects performed a comprehensive metabolic analysis including measurement of Resting Energy Expenditure using indirect calorimetry, bioimpedance, and body size measures. Physical activity was assessed using a Stanford 7 day recall questionnaire.

Data Analysis The data analysed will include determining the relationship between level of kidney disease as measured by eGFR and energy expenditure measured as Resting Energy Expenditure and doubly-labelled water Total Energy Expenditure. This will be determined by regression analysis. Additionally, comparison will be made between subjects with early-moderate (CKD stage 1-3) and advanced (CKD stage 4-5) CKD.

Inclusion Criteria:

1. CKD stages 1-5 according to the MDRD equation eGFR
2. Age >18

Exclusion Criteria:

1. Abnormal thyroid stimulating hormone level or previous thyroid disorder
2. Active malignancy
3. Pregnancy
4. Intercurrent illness or infection
5. Hospital admission in month prior to enrolment
6. Surgery in 4 weeks prior to enrolment
7. HIV, Hepatitis B, Hepatitis C positive status
8. Tuberculosis in the 12 months prior to enrolment.
9. Active vasculitis or connective tissue disorder
10. Organ transplantation.
11. Treatment with immunosuppression, except low dose corticosteroids (<10mg/day prednisolone).

Patients with chronic kidney disease who attended the renal clinics of the East and North Herts NHS Trust