***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: OBJECTIVE To investigate whether protein intake influences the decline in energy expenditure during energy restriction . DESIGN Cross-over study of three diets of 4.2 MJ/d for 7 days : one diet with 36 % energy as protein and two with 15 % energy as protein , one high in carbohydrate and the other high in fat . SUBJECTS Two men and six women aged 31 - 57 y. BMI 27.B-34.1 kg/m2 . MEASUREMENTS 24-h energy expenditure ( 24-h EE ) , sleeping metabolic rate ( SMR ) and body weight on days 0 and 7 of each diet ; 24-h urinary nitrogen excretion ( 24-h UN ) on days 0 - 7 of each diet . RESULTS 24-h EE and SMR declined on all three diets but the decrease was significantly less on the high protein diet than on the two low protein diets .  Weight loss was similar on all three diets . 24-h UN was less than N intake on the high protein diet but greater than N intake on the two low protein diets . CONCLUSIONS Maintaining protein intake reduces the decrease in energy expenditure during energy restriction We measured energy expenditure ( MREE ) and nitrogen excretion ( UUN ) in patients with severe head injury r and omized to early parenteral ( TPN , n = 21 ) or jejunal ( ENT , n = 27 ) feeding  with identical formulations . The MREE rose to 2400 + /- 531 kcal/day in both groups and remained at 135 % + /- 26 % to 146 % + /- 42 % of predicted energy expenditure over 4 weeks . Nitrogen excretion peaked the second week at 33.4 + /- 10 ( TPN ) and 31.2 + /- 7.5 ( ENT ) g N/day . Both routes were equally effective at meeting nutritional goals ( 1.2 x MREE , 2.5 g protein/kg/day intake , stabilized albumin and transferrin levels ) . Infections were equally frequent : 1.86 episodes/TPN patient versus 1.89 episodes/ENT patient . While patient charges were much greater for TPN , the hospital costs were similar for TPN and ENT support regimens . These findings show that patients with head injuries are hypermetabolic for weeks , that only 27 % are capable of spontaneously eating nutritional requirements by discharge , and that either TPN or ENT support is equally effective when prescribed according to individual measurements of MREE and nitrogen excretion Metabolic effects of increasing nitrogen intake during total parenteral nutrition ( TPN ) were studied in nine septic patients . The patients were given 5 % dextrose ( D5W ) for 1 d. For the next 6 d they received total parenteral nutrition ( TPN ) , at 1.35 times resting energy expenditure ( REE ) , containing either 191 or 366 mg N/(kg.d ) Non-protein calories were divided equally between glucose and lipid emulsion .  Three patients were studied on both diets ( n = 6 for each diet ) . On the high- but not the low-N diet were significant increases in protein oxidation , blood urea N , O2 consumption , and CO2 production .  TPN normalized most plasma amino acid levels but intramuscular amino acids remained unchanged . Transient positive N balance occurred during days 1 - 3 on the high- but not the low-N intake ; on days 5 - 6 N balance did not differ significantly from zero on either diet and the improvement ( 165 mg N/[kg.d ] ) was the same for both diets The aim of the study was to assess the total energy expenditure ( TEE ) , resting energy expenditure ( REE ) and physical activity level ( PAL ) in home-living cachectic patients with advanced pancreatic cancer . The influence of an energy and protein dense oral supplement either enriched with or without the n-3 fatty acid eicosapentaenoic acid ( EPA ) and administered over an 8-week period was also determined . In total , 24 patients were studied at baseline . The total energy expenditure was measured using doubly labelled water and REE determined by indirect calorimetry . Patients were studied at baseline and then r and omised to either oral nutritional supplement . Measurements were repeated at 8 weeks . At baseline , REE was increased compared with predicted values for healthy individuals ( 1387(42 ) vs 1268(32 ) kcal day−1 , P=0.001 ) , but TEE ( 1732(82 ) vs 1903(48 ) kcal day−1 , P=0.023 ) and PAL ( 1.24(0.04 ) vs 1.50 ) were reduced . After 8 weeks , the REE , TEE and PAL of patients who received the control supplement did not change significantly . In contrast , although REE did not change , TEE and PAL increased significantly in those who received the n-3 ( EPA ) enriched supplement . In summary , patients with advanced pancreatic cancer  were hypermetabolic . However , TEE was reduced and this was secondary to a reduction in physical activity . The control energy and protein dense oral supplement did not influence the physical activity component of TEE . In contrast , administration of the supplement enriched with EPA was associated with an increase in physical activity , which may reflect improved quality of life A prospect i ve trial was conducted in 20 surgical intensive care unit patients receiving mechanical ventilation to compare estimates of resting energy expenditure ( REE ) with the measured values . The 12 women and 8 men ( mean age 61.7±2.8 ( s.e.m . ) years ) underwent a full nutritional assessment before measurement of their REE by indirect calorimetry using the MGM II metabolic cart ( Utah Medical ) . Their REE was estimated by the Harris‐Benedict formula ( mean 1324±53 ( s.e.m . ) kcal/day ) as well as an empirical formula ( where empirical formula = 22 × body weight in kg ) ( 1370 ± 68 ( s.e.m . ) kcal/day ) . Results by either estimate were not statistically different from the measured resting energy expenditure ( MREE ) ( 1382±130 ( s.e.m . ) kcal/day ) , by one‐way analysis of variance . No multiplication factors were needed to relate the Harris–‐Benedict formula to MREE in this critically ill population and the estimate by the empirical formula was as good and simpler to perform . Although values by the Harris — Benedict formula and empirical formula correlated significantly with MREE ( P<0.05 ) the correlation coefficients were low : 0.48 and 0.45 respectively . Thus , mean estimates were excellent for the group but less predictive for the individual . Multiple linear regressions did reveal that body composition and metabolic stress were of greater predictive value , since an equation relating weight ( P<0.003 ) , sex ( P<0.003 ) , white blood cell count ( P < 0.003 ) and 24‐h urinary creatinine excretion ( P < 0.05 ) could predict 76 per cent of the variation ( r = 0.87 ) in the MREE with an overall significance of P = 0.0002 . Given the importance of matching energy intake to needs in many critically ill patients who are mechanically ventilated , accurate measurement of the REE is recommended now that instrumentation is equal to the task OBJECTIVES We measured the energy and protein needs in 50 sequential , critically ill , ventilated patients requiring continuous renal replacement therapy ( CRRT ) for renal failure by using indirect calorimetry and three sequential isocaloric protein-feeding regimes of 1.5 , 2.0 , and 2.5 g. kg(-1 ) . d(-1 ) . We also assessed the compliance of actual feeding with target feeding and correlated the predictive energy requirements of the formulae with the actual energy expenditure ( EE ) measured by indirect calorimetry . We also determined whether these feeding regimes affected patient outcome . METHODS The energy and protein needs of 50 consecutive , critically ill patients ( 31 male ; age 53.3 + /- 17.4 y ; Acute Physiology and Chronic Health Evaluation ( APACHE II ) score : 26.0 + /- 8.0 ; Acute Physiology and Chronic Health Evaluation score predicted risk of death : 50.0 + /- 25.0 % ) were assessed by using indirect calorimetry and ultrafiltrate nitrogen loss . Entry into this study was on commencement of CRRT . To eliminate any beneficial effect from the passage of time on nitrogen balance , 10 of the 50 patients were r and omized to receive 2.0 g. kg(-1 ) . d(-1 ) throughout the study , and the others received an escalating isocaloric feeding regime ( 1.5 , 2.0 , and 2.5 g. kg(-1 ) . d(-1 ) ) at 48-h intervals . Enteral feeding was preferred , but if this was not tolerated or unable to meet target , it was supplemented or replaced by a continuous infusion of total parenteral nutrition . Energy was given to meet caloric requirements as predicted by the Schofield equation corrected by stress factors or based on the metabolic cart readings of EE and was kept constant for all patients throughout the trial . Patients were stabilized on each feeding regime for at least 24 h before sample s of dialysate were taken for nitrogen analysis at 8-h intervals on the second day . CRRT was performed by using a blood pump with a blood flow of 100 to 175 mL/min . Dialysate was pumped in and out counter-currently to the blood flow at 2 L/h . A biocompatible polyacrylonitrile hemofilter was used in all cases . RESULTS EE was 2153 + /- 380 cal/d and increased by 56 + /- 24 cal/d ( P < 0.0001 ) throughout the 6-d study period to 2431 + /- 498 cal/d . At study entry , the mean predicted ( Schofield ) caloric requirement was 2101 + /- 410 . Patients received 99 % of the predicted energy requirements . However , the mean EE was 11 % higher at 2336 + /- 482 calories . This difference was not uniform . If the predicted caloric requirement was less than 2500 , the EE exceeded the predicted by an average of 19 % . If the predicted caloric requirement was greater than 2500 , the EE on average was 6 % less than predicted . This relation was significant ( P = 0.025 ) and has not been described previously . Nitrogen balance was inversely related to EE ( P = 0.05 ) , positively related to protein intake ( P = 0.0075 ) , and more likely to be attained with protein intakes larger than 2 g. kg(-1 ) . d(-1 ) ( P = 0.0001 ) . Nitrogen balance became positive in trial patients over time but were negative in control patients over time ( P = 0.0001 ) . Nitrogen balance was directly associated with hospital outcome ( P = 0.03 ) and intensive care unit outcome ( P = 0.02 ) . For every 1-g/d increase in nitrogen balance , the probability of survival increased by 21 % ( P = 0.03 ; odds ratio , 1.211 ; 95 % confidence limits , 1.017,1.443 ) . Further , although enterally and parenterally fed patients had lower mortalities than predicted , the presence of enteral feeding , even after adjusting for predicted risk of death , had a statistically significant benefit to patient outcome ( P = 0.04 ) . CONCLUSIONS This study found that a metabolic cart can improve the accuracy of energy provision and that a protein intake of 2.5 g. kg(-1 ) . d(-1 ) in these patients increases the likelihood of achieving a positive nitrogen balance and improving survival .  Enteral feeding is preferable , but if this is not possible or does not achieve the target , then it should be supplemented by parenteral feeding The metabolic effects of TPN were studied in a selected group of trauma patients . Nineteen patients were r and omly divided into two groups : the first was treated with glucose and insulin , the second with glucose , insulin and amino acids . Each patient in both groups received TPN isocaloric with respect to daily energy output and the treatment lasted five days . Each group was further divided into two subsets ( severe or moderate catabolism ) according to fasting energy output with respect to the expected energy expenditure . During the acute flow phase , both in moderate as well as in severe catabolism , glucose and insulin were effective for protein sparing ; the maximum protein sparing effect was reached when giving a caloric intake equal to 130 % of daily energy output . Glucose , insulin and amino acids were effective in replacement of nitrogen losses . In moderately catabolic patients nitrogen balance was significantly better than in severely catabolic patients . This study shows that early and short-term TPN is effective in controlling the flow phase of trauma .  Glucose and insulin  appear to be the determinants of the protein sparing effect when given in amounts equal to those needed ; amino acids provided protein replacement when given in amounts equal to about 20 % of energy output . Energy supply higher than 120–130 % of daily energy output does not increase protein sparing and protein replacement , the only effect being a further increase in metabolism , which is possibly dangerous in critically ill patients The effects of increasing nitrogen intake were studied in 10 nutritionally depleted patients receiving total parenteral nutrition . After 1 to 2 days on 5 % dextrose , the patients received , in r and om order , intravenous diets containing either a low ( 18 
    Output:
    
The E/N ratio is not a constant value but decreases continuously with increasing protein loss .