crohn s disease ( cd ) is a chronic inflammatory disease of the digestive tract of unknown etiology . are common features , and nutritional deficiencies occur in cd patients in both active and remission phases . emaciation is found in 2075% of patients with cd [ 1 , 2 ] , and approximately 75% of hospitalized cd patients are undernourished [ 3 , 4 ] . malnutrition in cd patients is associated with decreased dietary intake , malabsorption , and protein - losing enteropathy . furthermore , micronutrient deficiencies including vitamin d , vitamin b12 , folic acid , zinc and selenium are frequent in these patients [ 58 ] . nutritional support is essential for cd patients , and nutritional therapy such as enteral nutrition ( en ) or total parenteral nutrition ( tpn ) has been established as primary therapy for cd as well as infliximab therapy and steroid therapy . especially , elemental diet therapies are effective in both induction and maintenance therapies [ 911 ] , although their therapeutic mechanisms are still unknown . . however , melchior et al .   reported that measured ree ( mree ) was approximately 33  kcal / kg / day in patients with cd , which was lower than the ree observed in other diseases . furthermore , schneeweiss et al .   reported that mree was not significantly different between cd patients and healthy subjects . in japan , nutritional therapies such as en or tpn therapies are widely accepted , but energy metabolism in japanese patients with cd remains unclear . total energy of en or tpn is usually determined by using predicted resting energy expenditure ( pree ) calculated by the harris - benedict equation , and total energy requirements are calculated by pree    active factor    stress factor . on the other hand , mree can be determined by indirect calorimetry . theoretically , pree is equal to mree in healthy humans , and mree / pbee ratios are markers of hyper - metabolic status . in this study , we evaluated energy metabolism in japanese patients with cd and suggested optimal energy requirements for nutritional therapies . sixteen patients with cd ( 5 women and 11 men , median age 36 years old ) and 8 healthy volunteers were enrolled in this study . all patients had the diagnosis of cd established by radiological , histological , and clinical criteria . among these patients , two patients had colitic disease , six patients had ileal disease and eight patients had ileocolitic disease . infliximab therapy has just been started in four patients , and ( oral ) prednisone ( 1030  mg / day ) was taken by five patients . mrees and respiratory quotients ( rq ) were measured by computed open - circuit indirect calorimetery ( ae-300s ; minato medical science co. , osaka , japan ) . indirect calorimetry ( ic ) was performed in the hospital room the morning after a 10-h overnight fasting , but infusion of total parenteral nutrition solution were kept on going . period flow and gas calibration were performed prior to measurements . after resting for a minimum of 30  min , after equilibrium was reached for 10  min , respiratory exchange was performed continuously over 30  min . mree was calculated from oxygen consumption ( vo2 ) and carbon dioxide production ( vco2 ) by the weir equation . mree  =  ( 3.94    vo2  +  1.11    vco2 )    1.44 measurement of the rq was calculated as rq  =  vco2/vo2 . man ; pree  =  66.47  +  13.75    w  +  5.0    h    6.75    a woman ; pree  =  665.09  +  9.56    w  +  1.84    h    4.67    a where pree stands for resting energy expenditure ( kcal / day ) , w for weight ( kg ) , h for height ( cm ) and a for age ( years ) . differences between groups were analyzed with kruskal - wallis tests . a p value < 0.05 was considered to be statistically significant . sixteen patients with cd ( 5 women and 11 men , median age 36 years old ) and 8 healthy volunteers were enrolled in this study . all patients had the diagnosis of cd established by radiological , histological , and clinical criteria . among these patients , two patients had colitic disease , six patients had ileal disease and eight patients had ileocolitic disease . infliximab therapy has just been started in four patients , and ( oral ) prednisone ( 1030  mg / day ) was taken by five patients . mrees and respiratory quotients ( rq ) were measured by computed open - circuit indirect calorimetery ( ae-300s ; minato medical science co. , osaka , japan ) . indirect calorimetry ( ic ) was performed in the hospital room the morning after a 10-h overnight fasting , but infusion of total parenteral nutrition solution were kept on going . period flow and gas calibration were performed prior to measurements . after resting for a minimum of 30  min , patients were assessed in a supine position with a facemask . after equilibrium was reached for 10  min , respiratory exchange was performed continuously over 30  min . mree was calculated from oxygen consumption ( vo2 ) and carbon dioxide production ( vco2 ) by the weir equation . mree  =  ( 3.94    vo2  +  1.11    vco2 )    1.44 measurement of the rq was calculated as rq  =  vco2/vo2 . man ; pree  =  66.47  +  13.75    w  +  5.0    h    6.75    a woman ; pree  =  665.09  +  9.56    w  +  1.84    h 4.67    a where pree stands for resting energy expenditure ( kcal / day ) , w for weight ( kg ) , h for height ( cm ) and a for age ( years ) . differences between groups were analyzed with kruskal - wallis tests . a p value < 0.05 was considered to be statistically significant . patients were not significantly different from control subjects in age and height , but had significantly lower body weights , and thus lower bmis ( table  1 ) . crohn s disease activity index from these patients was 231.3    84.8 , and c - reactive protein was 3.24    4.6  mg / dl . average hemoglobin , red blood cell count , white blood cell count and platelet count were 10.64    2.1  g / dl , 400.8    62.6    10/mm , 7540   3490/mm , 35.4    12.2    10/mm respectively . serum albumin and total - cholesterol is 3.46    0.44  g / dl and 127.9   47.6  mg / dl . in cd patients , mree determined by indirect calorimetry was 1271    181.7  kcal / day and pree calculated by the harris - benedict equation was 1372.7    143.7  kcal / day , respectively . as shown in fig .  1 , there were significant correlations between mree and pree in cd patients ( p<0.001 ) as well as in healthy controls ( p<0.05 ) . both mree and pree in cd patients were slightly lower than those of healthy controls , but there was no significant difference . on the other hand , mree / body weight of cd patients ( 24.4    2.4  kcal / kg / day ) was significantly higher than that of healthy control subjects ( 21.3    1.7  kcal / kg / day ) ( table  1 ) . similarly , pree / body weight of cd patients ( 26.4    2.6 kcal / kg / day ) was also significantly higher than that of healthy control subjects ( 22.9    2.6  kcal / kg / day ) ( table  1 ) . in cd patients , mree / body weight was significantly lower than pree / body weight ( 26.4    2.5  kcal / kg / day ) ( fig .  2 ) . in only two patients , mree / body weight was higher than pbee / body weight , and one of them developed complications including an abdominal abscess with fever . rq in these patients was 0.94    0.14 , and there were significant positive correlations between mree and rq ( fig . 3 ) , whereas there were no significant correlations between mree and rq in healthy controls ( p  =  0.075 ) . however , there were no significant correlations between mree and bmi , or between rq and bmi in cd patients . subjects were also categorized into two groups based on body mass index ( group a ; < 18.5 vs group b ; > 18.5 ) . there were no significant differences in height , body weight , pree , mree and between groups , but there were significant differences in pree / body weight ( p<0.021 ) . the mree / body weight in group a ( 24.7    1.2 kcal / kg / day ) was almost same as that of group b ( 24.1    3.0 kcal / kg / day ) . this study showed that measured ree by ic in hospitalized cd patients was 24.4    2.4  kcal / kg / day , and this was significantly higher than that in healthy controls . this result suggests that cd patients apparently have a hyper - metabolic status , and supports observations from previous studies [ 1216 ] . however , mree was significantly lower than pree calculated by the harris - benedict equation in cd patients . usually , energy requirements in hospitalized patients are calculated by pree    active factor    stress factor . stress factor in patients with inflammatory bowel disease is recommended as 1.11.3   as well as in patients with cancer and chronic obstructive pulmonary disease . this adjustment may result in the actual energy expenditure as approximately 45  kcal / kg / day . however , barot et al . reported that the pbee was equivalent to mree in non - septic cd patients . they decided that energy requirement were often not greater than the predicted requirement by pree    active factor   stress factor . the inflammatory bowel disease study group of the japanese ministry of health , labor and welfare also recommends that total energy of tpn or en should be 4045  kcal / ideal body weight / day in active cd patients . kcal / kg / day ( 2530  kcal / ideal body weight ) may be ideal as total energy for en or tpn therapies for cd patients by calculating ree    1.21.3 as the active factor . cd patients certainly have hyper - metabolic statuses , and but high - energy intakes during en or tpn therapies may have a risk of overfeeding . european guidelines   recommend that 2530  kcal / ideal body weight / day is optimal for active crohn s disease . a previous study showed that rq in active cd is significant lower than in health controls ( cd patients ; 0.78    0.05 versus healthy controls ; 0.86    0.05 ) and energy metabolism in active cd resembled starvation patterns . in this study , there is a positive correlation between mree / body weight and rq , and this finding shows that fat is mainly oxidated in low metabolic patients . however , the present results revealed that ( the mean ) rq in hospitalized cd patients was 0.93    0.14 , and there was no significant difference from that found in controls . furthermore , there was no significant difference between rq and bmi , and rq was lower than 0.8 in only a few subjects ( 12.5% ) . the aforementioned result may be explained by the fact that our patients had already received nutritional therapy . based on these observations , our results did not support a previous report that energy metabolism of active cd patients mimic starvation patterns . it has long been hypothesized that increased energy expenditure contributes to weight loss in patients with cd . however , vaisman et al .   reported that mree / pree was higher in a well - nourished cd group than in an undernourished cd group . in this study , mree / body weight in the undernourished group was found to be equivalent to that in well - nourished group , and mree / pree was slightly higher in the well - nourished group than the undernourished group . these observations support that increased energy expenditure is not a contributor to the underweight status of cd patients . however , patients receiving this oral steroid were few in this study ( 31.2% ) . reported that ree did not change after infliximab therapy , whereas rq increased after infliximab therapy . their result revealed that lipolysis decreased and starvation improved in cd patients receiving infliximab therapy . infliximab therapy is now going to be a main therapeutic tool in active cd patients , but nutritional management is necessary in these patients . ree and rq determinations by indirect calorimetry are useful for cd patients receiving infliximab therapy as well as nutritional therapies . in conclusion nutritional therapies consisting of 2530  kcal / ideal body weight / day are recommended as optimal for active cd patients .