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European Journal of Nutrition (2022) 2804-3ORIGINAL CONTRIBUTIONIntermittent fasting and continuous energy restriction result in similarchanges in body composition and muscle strength when combinedwith a 12 week resistance training programStephen J. Keenan1 · Matthew B. Cooke1,2 · Ebrahim Bani Hassan2,3Sam X. Wu1 · Doa El‑Ansary1,4 · Mahdi Imani2,3 · Regina Belski1· Won Sun Chen1· Josef Sullivan1 ·Received: 14 October 2021 / Accepted: 6 January 2022 / Published online: 27 January 2022 The Author(s) 2022AbstractPurpose The objective of this study was to compare the effects of 12 weeks of resistance training combined with either 5:2intermittent fasting or continuous energy restriction on body composition, muscle size and quality, and upper and lowerbody strength.Methods Untrained individuals undertook 12 weeks of resistance training plus either continuous energy restriction [20%daily energy restriction (CERT)] or 5:2 intermittent fasting [ 70% energy restriction 2 days/week, euenergetic consumption5 days/week (IFT)], with both groups prescribed a mean of 1.4 g of protein per kilogram of body weight per day. Participants completed 2 supervised resistance and 1 unsupervised aerobic/resistance training combination session per week.Changes in lean body mass (LBM), thigh muscle size and quality, strength and dietary intake were assessed.Results Thirty-four participants completed the study (CERT 17, IFT 17). LBM was significantly increased ( 3.7%,p 0.001) and body weight ( 4.6%, p 0.001) and fat ( 24.1%, p 0.001) were significantly reduced with no significantdifference between groups, though results differed by sex. Both groups showed improvements in thigh muscle size andquality, and reduced intramuscular and subcutaneous fat assessed by ultrasonography and peripheral quantitative computedtomography (pQCT), respectively. The CERT group demonstrated a significant increase in muscle surface area assessed bypQCT compared to the IFT group. Similar gains in upper and lower body strength and muscular endurance were observedbetween groups.Conclusion When combined with resistance training and moderate protein intake, continuous energy restriction and5:2 intermittent fasting resulted in similar improvements in body composition, muscle quality, and strength. ACTRN:ACTRN12620000920998, September 2020, retrospectively registered.Keywords Intermittent fasting · Continuous energy restriction · Resistance training · Body composition · Lean body mass ·Weight loss* Stephen J. [email protected] of Health, Arts and Design, School of HealthSciences, Swinburne University of Technology, John Street,Hawthorn, Melbourne, VIC 3122, Australia2Australian Institute for Musculoskeletal Science (AIMSS),The University of Melbourne, Melbourne, VIC, Australia3Department of Medicine, Western Health, MelbourneMedical School, The University of Melbourne, Melbourne,VIC, Australia4Department of Surgery, Melbourne Medical School, TheUniversity of Melbourne, Melbourne, VIC, AustraliaAbbreviationsCSA Cross-sectional areaCERT Continuous energy restriction plus training groupDXA Dual x-ray absorptiometryEI EchogenicityIFT Intermittent fasting plus training groupLBM Lean body massMPB Muscle protein breakdownMPS Muscle protein synthesispQCT Peripheral quantitative computed tomographyRF Rectus femorisVI Vastus intermedius1RM 1-Repetition maximum3RM 3-Repetition maximum13Vol.:(0123456789)

2184IntroductionEnergy-restricted diets are becoming increasingly popularamongst individuals for a variety of reasons, includingimproving body composition and general health and wellbeing. Regardless of the reason, these diets commonly leadto weight loss in the form of both fat and lean body mass(LBM) [1]. While fat loss is usually desirable, reductionsin skeletal muscle mass (a major component of LBM) maylead to a number of deleterious short- and long-term consequences, such as hyperphagia and reduced basal metabolic rate, which may compromise long term weight losssuccess [2]; increased risk of strength loss and disability,especially in older adults [3, 4]; and potential metabolicissues incumbent with low muscle mass [5].The mechanisms behind weight-loss-induced reductionsin LBM are not fully understood, however; the impact ofenergy restriction on protein turnover and net muscleprotein balance may be a contributing factor [6]. Skeletalmuscle mass is determined by a balance between muscleprotein synthesis (MPS) and muscle protein breakdown(MPB), which remains equal during energy balance [7].Conversely, during short-term, continuous energy restriction, both post-prandial and post-absorptive MPS arereduced [8], which may lead to an overall negative protein balance, higher protein catabolism to supply aminoacids and reductions in muscle mass [6]. Whether thisalso occurs over extended periods of energy restriction isunclear [9]. Notwithstanding, higher protein intakes, and/or performing resistance training have been shown to partially or completely attenuate these reductions in MPS [6,10]. Moreover, these strategies, as well as others includingslower rates of weight loss, have been utilised to successfully mitigate LBM loss during longer periods of energyrestriction [1, 11].Recently, interest in how the pattern of energy restrictionaffects changes in LBM during weight loss has increased.Compared to traditional energy-restricted diets that are characterised by moderate daily energy restriction (i.e. continuous energy restriction), alternative patterns such as intermittent fasting where periods of severe energy restriction areinterspersed with regular dietary or ad libitum consumption might provide greater protection against LBM loss.Although evidence to support this is currently lacking [12],it seems plausible that short-term periods of energy balanceor surplus, especially in close proximity to resistance training, may promote greater maintenance and accrual of LBMthan continuous periods of energy restriction/deficit. Thiscould be via greater output during training due to increasedenergy availability, or differences in acute changes in MPSand anabolic hormonal responses during periods of energybalance/surplus compared to energy deficit [8, 13].13European Journal of Nutrition (2022) 61:2183–2199A popular variation of intermittent fasting is the 5:2 fasting diet, which generally involves 2 days per week of severe(consumption of 1600–3000 kJ/day) or complete energyrestriction, paired with 5 days of ad libitum or euenergeticconsumption [14, 15]. Despite widespread public popularity of the 5:2 intermittent fasting model, little research hasinvestigated its effects on LBM compared to a continuousenergy restriction diet, especially when combined with aresistance training program and higher protein intake [16].Moreover, only a handful of intermittent fasting studies haveutilised more sensitive assessments of muscle hypertrophy(e.g. ultrasonography) to simultaneously assess changesin muscle growth [17–20]. Thus, the purpose of this studywas to investigate and compare the effects of 12 weeks ofresistance training combined with either a 5:2 intermittentfasting or continuous energy restriction style diet matchedfor energy and protein intake on body composition (especially LBM), indicators of muscle hypertrophy and quality,and upper and lower body strength. The primary outcomeof this study was a change in LBM. It was hypothesisedthat 5:2 intermittent fasting would result in maintenance orgreater accrual of LBM compared with continuous energyrestriction.MethodsParticipantsParticipants were recruited through advertising on socialmedia channels targeting current and past university studentsin Victoria, Australia. A total of 194 individuals respondedto the advertisement and underwent initial screening. Only44 were deemed eligible and were recruited for the study.Participants were eligible for inclusion if they: (i) were agedbetween 18 and 45 years; (ii) had a body mass index (BMI)of 22.0–35.0 kg/m2; (iii) had a body fat percentage 18%for males or 25% for females as measured via dual x-rayabsorptiometry (DXA); (iv) had not followed a structuredresistance training program in the previous 6 months and; (v)had been weight stable for 3 months prior to the study ( 5%weight loss or weight gain). Participants were excluded ifthey: (i) were smokers; (ii) had diabetes; (iii) had a historyof cardiovascular disease; (iv) were taking dietary supplements and were unwilling to cease these for the durationof the study; (v) were taking glucose or lipid lowering, orweight loss medication; (vi) had a current physical condition that may have been exacerbated by resistance training as determined by their general practitioner, (vii) werepregnant or intended to become pregnant in the following3–4 months; (viii) were menopausal or post-menopausal;(ix) had a history of disordered eating; (x) had a current orprevious respiratory condition likely to be exacerbated by

European Journal of Nutrition (2022) 61:2183–2199the intervention; (xi) had a current or previous gastrointestinal disorder likely to be exacerbated by the intervention;(xii) had any allergy to any components of the supplementproduct to be supplied; (xiii) were unable to commit to fasting on assigned days if randomised to the intermittent fastinggroup; (xiv) did not speak English at a level at which theywere able to understand and complete the requirements ofthe study or; (xv) disclosed any other chronic disease or condition, or were taking any other medication that investigatorsdeemed would contraindicate the study intervention.Randomisation and study overviewParticipants who were eligible for the study were stratifiedby age, sex and BMI before being randomised by coin tossinto either the intermittent fasting plus training (IFT) or continuous energy restriction plus training (CERT) groups for12 weeks. The random allocation sequence was not explicitly concealed. Participants in the IFT group undertook a5:2 style-fasting protocol, while those in the CERT group2185undertook a continuous energy restriction style feeding pattern. Both groups completed supervised resistance trainingtwice per week, and resistance/aerobic combination trainingonce per week. The intervention took place from February toNovember 2019, spread across 6 groups, starting 2–4 weeksapart. A flow chart showing participant movement throughthe study can be seen in Fig. 1. This study was approved bythe Swinburne University of Technology Human ResearchEthics Committee (project #2018/322).Diet protocolBasal energy requirements for all participants were calculated using the Mifflin St. Jeor equation [21], with totalenergy requirements calculated by applying an activity factor of 1.4 representing a recreational level of activity (basedon prescribed exercise). At the beginning of the interventionperiod, all participants were provided with example mealplans that would result in mean consumption of approximately 80% of estimated energy requirements and 1.4 g ofFig. 1  Participant flow diagram13

2186European Journal of Nutrition (2022) 61:2183–2199protein per kilogram of body weight per day (g/kg/day) overthe 12 week intervention. Meal plans were customised basedon food preferences for each individual and provided by adietitian along with brief education on the Australian healthyeating guidelines [22]. As participants in the IFT group hadlimited energy available on fasting days to reach recommended protein intakes, they were provided with proteinshakes and high protein soups to get as close to daily protein intake recommendations as possible. Participants werealso instructed on how to use the Easy Diet Diary (XyrisSoftware, Australia, 2019) smartphone application to recordtheir food, and substitute other foods of their choosing intothe meal plans while maintaining the same energy and protein intake.the differences between patterns of dietary intake while controlling for overall intake as much as possible.Continuous energy restrictionThose randomised to the CERT group were instructed toconsume 80% of their total energy requirements daily forthe duration of the 12 week intervention. This group represented a best practice ‘control’ group, as moderate energyrestriction (15–30%) is most commonly recommended forweight loss [25, 26]. Furthermore, participants were alsoprescribed consumption of 1.4 g/kg/day of protein. Participants in this group also received customised meal plans andthe same education as those in the IFT group.Intermittent fasting diet protocolExercise protocolAll participants in the IFT group were instructed to consume 100% of their energy requirements for 5 days perweek (non-fasting days). On two non-consecutive and nontraining days, participants consumed approximately 30% oftheir estimated energy requirements ( 2100 kJ for femalesand 2500 kJ for males) (fasting days), consistent with previous research [23, 24]. On fasting days, participants wereprescribed a diet consisting of whey-based protein shakes(Formulite), high-protein soups and steamed/raw vegetables. The macronutrient composition of these supplementsand the recommended intake on fasting days can be seen inTable 1. On fasting days, participants were asked to consume all energy during a 6 h window between 12.00 pm and6.00 pm, to ensure an extended fasting period, but also allowflexibility of consumption to promote compliance. Further,they were allowed ad libitum consumption of non-energyproviding beverages on fasting days. To match proteinintakes across dietary groups as closely as possible, thosein the IFT group were instructed to consume approximately1.5 g/kg/day of protein on non-fasting days, as their fasting day diets only provided 1.1–1.2 g/kg/day. This designresulted in the prescription of a 20% energy deficit and amean intake of protein of 1.4 g/kg/day, designed to be isoenergetic and isonitrogenous with the CERT group to exploreAll participants were required to undertake 3 training sessions each week: 2 resistance training sessions and 1 bodyweight aerobic/resistance training combination session.Training frequency of 3 times per week was seen as practical for the untrained participants, allowing adequate time forrecovery, but also the stimulus for muscle growth. The tworesistance training sessions were conducted at SwinburneUniversity’s Hawthorn campus, and were supervised by anaccredited strength and conditioning coach (who was alsothe study dietitian). The 2 supervised sessions consisted ofvariations of the following exercises: push-ups, squats, rows,lunges, bicep curls and dips (Supplemental Fig. 1). Theexercises utilised were chosen due to their lack of technicaldifficulty given the untrained population being researched.Participants completed these exercises in a superset styleworkout, aiming to complete 12–15 repetitions of eachexercise. Once participants were able to complete 3 sets of15 repetitions in any individual exercise, the weight wasincreased or exercise variation made more difficult, adhering to the principles of progressive overload. The one bodyweight aerobic/resistance training combination session perweek was completed by participants at home using bodyweight exercises consisting of planks, mountain climbers,crunches, burpees, lying side toe-touches and hip bridges.Table 1  Composition of fastingday meals consumed by IFTgroup and overall intake onfasting daysFoodsNutrientsEnergy (kJ/kcal)Protein (g)Carbohydrates (g)Fat (g)13MaleFemale2 meal replacement shakes1 high protein soup150 g raw/steamed vegetables1.5 meal replacement shakes1 high protein soup150 g raw/steamed vegetables2511/59793.630.4102080/49576.726.38

European Journal of Nutrition (2022) 61:2183–21992187These exercises were also completed using a superset formatwith 2 min breaks, however, were timed instead of countingrepetitions. When participants reached their time goal withgood form (self-assessed), they were instructed to increasethis by 5 s. All exercise sessions were conducted on nonfasting days in the IFT group to promote maximal energyavailability and avoid any detrimental effects of fasting onexercise performance.onto a personal computer for EI analysis using ImageJ software (NIH, Bethesda, MD) [29]. EI for RF and VI weremeasured utilising a standard square of 100 100 pixels,or where the predefined square did not fit within the crosssection of the muscle, the largest square that fit within theanatomic boundaries of the muscle was utilised, a methodwhich has shown good inter-observer reliability regardlessof the level of expertise [30].AssessmentsPeripheral quantitative computed tomography(pQCT)Bodyweight and body composition analysisWeekly weight measurements were taken in light clothingusing bioelectrical impedance scales [Multifrequency segmental body composition analyser; MC-780 Tanita Corporation (Tokyo, Japan)]. Lean body mass, fat mass and bodyfat percentage were assessed utilising dual x-ray absorptiometry [DXA; Hologic Horizon (Bedford MA)] at baselineand after the intervention period, as previously detailed [27].The DXA was calibrated for bone mineral density, muscleand fat masses on the morning of each assessment in accordance with manufacturer guidelines using spine and wholebody phantoms, respectively. Short and long-term coefficientof variation for these measurements were well within theacceptable level set by the manufacturer ( 5%).UltrasoundMuscle thickness, cross-sectional area (CSA) and musclequality [echogenicity (EI)], were measured using ultrasound (SonoSite M-Turbo, SonoSite Australasia Pty Ltd,New South Wales, Australia) with a linear array transducer(5–2 MHz) for the rectus femoris (RF) and vastus intermedius (VI) of the non-dominant leg at baseline and post intervention (Supplemental Fig. 2). All images were acquiredand analysed by the same technician. A fidelity check of theimage acquisition and analysis was conducted by a healthprofessional with over 10 years of experience in ultrasoundimaging and analysis. Varying depths were required toobtain full visualisation of the RF in some instances, however, the gain was kept consistent across measurements.Measurements were acquired with participants in a supineposition, with their knee in passive extension. Ultrasoundgel was applied to the transducer, which was placed perpendicular to the long axis of the anterior thigh, at a distance oftwo-thirds from the anterior, superior iliac spine to the superior patellar border, consistent with previous studies [28].Muscle thickness and CSA were measured in real-time withthe on-board functions of the M-turbo, utilising the straightline and tracing functions, respectively. Images were alsosaved onto the on-board hard drive before being transferredpQCT was utilised to measure the surface area of muscle,intramuscular fat and subcutaneous fat at baseline and postintervention (Supplemental Fig. 3). A single 2.5 mm transverse pQCT; (Stratec XCT3000, Stratec MedizintechnikGmbH, Pforzheim, Germany) scan with a voxel size of0.4 mm was obtained at mid-thigh region of the non-dominant leg. The mid-thigh was defined as midway betweenthe tip of the greater trochanter and medial edge of thetibial plateau, located by deep palpation. The images wereexported and further analyzed by Slice-O-Matic (Tomovision, Montreal, CA) to determine the muscle, intramuscularfat and subcutaneous fat volumes as previously described[31–33]. After visual checks; where due to beam hardeningartefacts the tissue was not segmented (“tagged”) optimally,the assignment of individual voxels or small voxel islandswere changed into the correct tissue manually, at the discretion of the operator. The pQCT was calibrated using themanufacturer’s phantom daily, with a coefficient of variationof 0.2%, as described previously [34].All imaging and image analyses were carried out by asingle experienced image analysis specialist (EB) or underhis direct supervision.Strength testingStrength testing was undertaken prior to the diet interventionand at the end of week 12. A 3 repetition maximum (3RM)test and strength endurance test were performed for bothbench press and leg press. While these exercises were notincluded within the resistance training program, these werechosen as a standardised method of strength testing usingsimilar movements to those included. After a brief 5 minwarm up, participants were instructed on correct lifting andbreathing techniques before practicing these using submaximal loads for 10–15 repetitions. Weight was gradually addedand repetitions reduced to serve as a functional warm up.Participants then completed a set of 3 repetitions at a selfselected weight close to their perceived capacity, followedby a 3 min rest, with weight being continually added to eachsubsequent attempt. 3RM was recorded as the last successfulattempt before form breakdown, or failure to complete the13

2188lift without assistance. The 3RM of each participant wasdetermined within 5 attempts. After the 3RM test, participants were allowed a 5 min rest before undergoing a strengthendurance test. These were tested in order such that 3RMbench press was followed by the bench press endurance test,and 3RM leg press was followed by the leg press endurancetest. Participants were required to complete as many repetitions as possible of each exercise utilising 70% of theirestimated 1 repetition maximum (1RM), calculated from theattained 3RM utilising the Brzycki formula [35] {weightlifted/[1.0278 – (0.0278 repetitions performed)]}. Failurewas determined as the first repetition where the participantrequired assistance. Repetitions where form was consideredinadequate were not counted; however, participants werenot stopped from completing subsequent repetitions if thisoccurred. Volume was calculated as the number of repetitions completed at 70% of 1RM multiplied by the weightlifted.Dietary intakeParticipants were required to keep a 3 day food diary atbaseline and in week 1, 6 and 12 using the Easy Diet Diary(Xyris Software, Australia, 2019) phone application. Thissoftware has been shown to produce results similar to other,more time-intensive methods of dietary data collection suchas 24 h recalls [36]. Participants recorded all food and drinkintake on non-consecutive days that included 2 weekdaysand 1 weekend day. Food records were kept on non-fastingdays for those in the IFT group. On fasting days, participantswere asked to note down any extra food or drink consumed,and whether they had consumed their recommended supplements. Intake on these days was estimated from theserecords.Statistical analysisChanges in LBM were considered the primary outcome ofthis study. Sample size calculations were conducted usingGPower version 3.1 [37] based on previous research showing a 2.4 kg loss of LBM in response to similar studymethodology to that of the current study in a comparablepopulation [38]. This was contrasted with research intointermittent fasting plus resistance or endurance training that has shown a minimal effect on LBM, albeit withsmaller reductions in weight [16, 23]. It was calculatedthat using an α error probability of 0.05 and power of 80%,22 participants would be required to detect a 2.4 kg difference in LBM between groups. Assuming a 33% attritionrate, total estimated sample size requirements were 29 participants. Results are presented as mean ( SD). Normality was assessed using the Shapiro–Wilk test and visualinspection of Q–Q plots. Assumptions of normality were13European Journal of Nutrition (2022) 61:2183–2199violated for intramuscular fat only. Intramuscular fat waslog10 transformed, resulting in normality. A linear mixedmodel with restricted maximum likelihood method wasestablished based on a first-order autoregressive structureand used to analyse variables for main effects for time,group and sex, and all possible 2-way and 3-way interactions, with BMI and age included as random effects dueto their inclusion as stratification variables. Differencesbetween groups at baseline were analysed using independent t tests. Bivariate correlations using Pearson’s correlation co-efficient were calculated to assess relationshipsbetween variables and changes in LBM. All analyses wereperformed using SPSS version 25 (IBM Corp, Armonk,NY, 2017). A p 0.05 was considered significant for alltests.ResultsParticipant characteristicsThere were a total of 17 completers in each group, with anearly even split of males and females (IFT 9 males and 8females, CERT 8 males and 9 females). Overall, 10 participants (n 8 female and n 2 male) failed to completethe interventions (CERT 5, IFT 5). Of these 10, 3 wereunable to commit to the exercise sessions, 2 were unable tocommit to the dietary protocol (IFT 1, CERT 1), and theremaining 5 dropped out due to unrelated medical issuesor relocation. Baseline characteristics for participants arepresented in Table 2. No significant differences were foundat baseline between groups as a whole, or when split by sex(Supplementary Table 1).Bodyweight and body composition analysisBodyweight and body composition measured before andafter the intervention are presented in Table 3. There was amain effect for time for weight, BMI, body fat mass, body fatpercentage and LBM, with significant reductions in weight,BMI, body fat mass and body fat percentage observedin both dietary groups, whereas LBM was significantlyincreased in both groups. There was also a main effect forsex for weight, LBM, fat mass and body fat percentage, withlower weight and LBM, but higher fat mass and body fatpercentage noted for females. A significant time x sex interaction was evident for weight, BMI and LBM, with largerreductions in weight and BMI observed in males, but greaterincreases in LBM observed in females. Individual changesin weight, LBM and body fat can be seen in SupplementaryFig. 4.

European Journal of Nutrition (2022) 61:2183–2199Table 2  Baseline participantcharacteristics2189Baseline variablesIFT(n 17; 9 males, 8females)CERT(n 17; 8 males, 9females)p valueaAge (years)Height (m)Weight (kg)BMI (kg/m2)LBM (kg)Body fat percentage (%)Bench press 3RM (kg)Bench press volume (70% 1RM) (kg)Leg Press 3RM (kg)Leg press volume (70% 1RM) (kg)24.7 (4.8)1.72 (0.1)80.1 (13.8)27.0 (2.7)54.3 (12.7)35.8 (8.6)43.3 (18.5)456.6 (229.1)112.1 (54.1)1223.6 (803.3)23.2 (3.9)1.71 (0.1)79.6 (13.5)27.1 (2.9)53.3 (13.1)36.7 (7.9)39.5 (19.5)376.6 (171.3)108.1 (65.8)999.1 n (SD)BMI body mass index, LBM lean body mass, 1RM 1 repetition maximum, 3RM 3 repetition maximumaP values reported are for independent t tests between intervention groupsMid‑thigh muscle surface area and intramuscularand subcutaneous fat analysispQCTMuscle surface area and intramuscular and subcutaneousfat measured before and after the intervention via pQCTare reported in Table 3. A main effect for time was foundfor subcutaneous fat and log10 intramuscular fat with significant reductions occurring in both groups over time. Amain effect for sex was also found for muscle surface areaand subcutaneous fat, with larger muscle surface area,but lower subcutaneous fat noted for males. There was atime x group effect for muscle surface area, with those inthe CERT group experiencing a mean increase in musclesurface area compared to the IFT group.UltrasoundRF thickness, CSA and EI, and VI thickness and EI measured before and after the intervention via ultrasound arepresented in Table 3. A main effect for time for RF thickness, RF CSA and RF EI was noted, with RF thicknessand CSA significantly increased in both groups over time,whereas RF EI significantly decreased in both groupsover time. A main effect for sex was also found for RFthickness, RF CSA and RF EI, with larger RF thicknessand CSA, but lower RF EI in males observed. There wereno other significant interactions or main effects identifiedfor RF measurements and/or all VI assessments.Dietary intake analysisParticipant dietary intake data measured before and duringthe intervention are summarised in Table 4. There was amain effect for time for overall mean absolute daily energyintake in kJ, relative energy intake in kJ/kg, relative protein intake in g/kg, relative carbohydrate intake in g/kg andrelative fat in g/kg, with significant reductions in energy(both absolute and relative), relative carbohydrate and fatintake identified across all groups, and a significant increasein relative protein intake. There was also a main effect forsex for mean absolute daily energy intake in kJ, with lowerconsumption in females. A significant time x sex interaction was found for relative energy intake (kJ/kg) and relative carbohydrate intake (g/kg), with females demonstrating greater reductions in energy and carbohydrate intakecompared to males during the intervention period. Averageenergy restriction for those in the IFT and CERT groupswere 31.0 5.9% and 29.3 6.5% for males and 33.9 7.1%and 28.1 6.1% for females respectively, with no significantdifference between groups overall (IFT 32.4 6.4% versusCERT 28.7 6.1%).Fasting versus non‑fasting days in IFT participantsDifferences in dietary energy and protein intake on fasting and non-fasting days for the IFT group are presentedin Table 5. Energy intake on fasting days for females wassignificantly lower in week 12 compared to week 1. No othersignificant differences between time points on fasting or nonfasting days were found.13

Body composition variablesIFT Males (n 9)BMI (kg/m2)CERT Males (n 8)IFT Females (n 8)CERT Females (n 9)Weight (kg)IFT Males (n 9)CERT Males (n 8)IFT Females (n 8)CERT Females (n 9)LBM (kg)IFT Males (n 9)CERT Males (n 8)IFT Females (n 8)CERT Females (n 9)Fat mass (kg)IFT Males (n 9)CERT Males (n 8)IFT Females (n 8)CERT Females (n 9)Body fat percentage (%) IFT Males (n 9)CERT Males (n 8)IFT Females (n 8)CERT Female

prescribed a diet consisting of whey-based protein shakes (Formulite), high-protein soups and steamed/raw vegeta-bles. The macronutrient composition of these supplements and the recommended intake on fasting days can be seen in Table 1. On fasting days, participants were asked to con