Resting Energy Expenditurein Anorexia Nervosa: A Case Report in Two Monozygotic Twins

1. Abstract

Introduction: Littleis known abou trestingenergy expenditure (REE) inpatients with anorexia nervosa (AN) duringrefeeding and after recovery, dueto the metabolic, body compositionandphy - sical activity changes. Methods:WepresentthecaseofayoungfemaleANpatientfollowedfor6-monthsduringrefeedingandhermonozygotictwinsister,currentlyhealthyafterhavingrecoveredfromanorexianerv osa 5yearsago.WemeasuredtheirREEandrespiratoryquotientbyindirectcalorimetry,andtheirbod y composition by bio- impedance analysis. Results:After6monthsrefeedingtheANpatientgained4.6kgoffatmass(FM)andlost3.3kg offat-freemass(FFM),resultinginnoweightgainandadecreaseofREEcomparedtothebaseline. HertwinsistershowedaprogressiveincreaseofbothFFM(2kg)andFM(1.5kg),howeverherRE E stayed unchanged and lower than predicted. Conclusion: This case highlights the negative impact of hyperactivity on body weight control duringthetreatmentofANandcallstheattentiontotheassociationbetweenfatfreemassandREE in former AN patients. The atypical low mREE we assessed, implies the role of other factors than fat-free mass in determining energy expenditure, and underlines the importance of measuring it to accurately define the individual caloric requirements.

2. Keywords

Energy expenditure; Fat mass; Fat-freemass;Anorexianervosa; Monozygotic twins

3. Introduction

Anorexia nervosa (AN) is characterized by restricted energy intake,anintensefearofgainingweightanddisturbedbodyimage. Severe food restriction causes changes in energy metabolism and body composition, with a loss of both fat mass and fat-free mass, thelatterbeingoneofthemajordeterminantofrestingenergyexpenditure(REE)[1].PatientsdiagnosedwithANhavebeenshown lower REE compared to individuals with normal body weight or constitutionally thin [2, 3]. However, after weight restoration, REE of recovered-anorexic patients was found to be comparable to those of control subjects [4]. ThiscasereportstheevolutionofREEandbodycompositionina youngANpatientafter3and6monthsofrefeeding,aswellasthe relationships between these parameters, compared to those of her monozygotictwinsister,currentlyhealthyafterhavingrecovered fromAN.

4. Materials&Methods

A27-yearoldwomanwasadmittedtothepsychiatricdayhospital for an evaluation and was diagnosed with a restrictive type AN. Herbodyweightwas39.5kg,withabodymassindex(BMI)of15.4 kg/m2,andaweightlossof6kginthelast10months.Thepatient presented amenorrhea, a pronounced body image disorder and a relativelyintensephysicalactivity(2to3hourswalkingperday). Duringteenageyears,apreviousmedicalcaretorestoreherweight resultedunsuccessful,becauseofanabsenceofaconcomitantpsy- cho behavioral therapy. The patient was submitted to a multidisciplinary psychiatric and psychotherapeutic outpatient care, individually and in group, for oneyear.Itwasfoundthat,thisanorexiawaspartofaglobalcomplexofanxio-depressivedisorder,focusedinparticularonherprofessional environment. The patient took part in the treatment programfor6months.TheANpatienthasamonozygotictwinsister, who suffered of AN between the age of 13 and 23 years old. The twin sister is currently healthy and has an active lifestyle. During the6monthswefollowedthemup,sheintensifiedtheamountsand typesofphysicalexerciseandincreasedenergyintakesfrom1800 kcal/dto2500kcal/d.WemeasuredtheirREEbyindirectcalorimetry(Q-NRG®,Cosmed,Italy),andtheirbodycompositionusing 50kHztetrapolarbioelectricalimpedanceanalysis(Nutriguard®, DataInput,Germany)oneweek,threeandsixmonthsaftertheAN patient started refeeding.

5. Results

Twins’ body characteristics and body composition during the 6 months follow-up are shown in Table 1. After3monthsrefeeding, the AN patient’s gained2. 2kg of fatmass andlost0.7kgoffatfreemass. After 6months, shegained 4.6kg of fatmassandlost 3.3kg off at-free mass compared to the baseline. The twin sister show edaprogres sivein crease of bothfat-freemass (2 kg) and fat mass (1.5 kg) in 6 months, reflecting the increment of physical activity and energy intake. REE measured by indirect calorimetry (mREE) and predicted by Harris-Benedict (pREE) are presented in Table 2.

6. Discussion

Similarly to previous investigations [5, 6], our case showed that theANpatient’smREEwaslowerthanpredicted.After3months refeeding,shegained2.2kgoffatmass,butnochangesinfat-free mass were observed, resulting in unmodified mREE. On the con- trary, the loss of fat-free mass after 6 months refeeding lead to a decrease in mREE. Despite the refeeding program, the patient showed no weight gain, probably due to the hyperactivity that we werenotabletocontrol.PhysicalactivityduringthecourseofAN has been reported an important modulator of body composition restoration.Availabledatasuggestthatmaintainedhyperactivityis an indicator of poor outcome and can impair weight gain, while programmed and personalized physical activity can be beneficial for the restoration of body composition [7, 8]. DifferentstudiesreportedasimilarrespiratoryquotientinANpatients and healthy controls, however we measured a higher respiratory quotient in the patient during the first months. This maybeexplainedasconsequenceoftherefeeding,whichimpliesareplenishment of glycogen stores and a reduction in fat catabolism [9,10].

7. Conclusion

This case highlights the negative impact of hyperactivity on body weightcontrolduringthetreatmentofAN.Apersonalizedphysicalactivityprogram,combinedtorefeeding,shouldbeconsidered to promote the restoration of body composition in AN patients. This case also calls the attention to the association between fatfreemassandREEinformerANpatients.TheatypicallowmREE

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Citation:

Pichard C. Resting Energy Expenditurein Anorexia Nervosa: A Case Report in Two Monozygotic Twins. Annals of Clinical and Medical Case Reports 2020