British Journl of Nutrition (27), pge 1 of 9 q The uthors 27 doi: 1.117/S7114781237 mternl junk food diet in pregnny nd lttion promotes n exerted tste for junk food nd greter propensity for oesity in rt offspring Stéphnie. Byol*, Smnth J. Frrington nd Neil C. Stiklnd The Royl Veterinry College, Royl College Street, Deprtment of Veterinry Bsi Sienes, London, NW1 TU, UK (Reeived 3 pril 27 Revised 26 June 27 epted 29 June 27) Oesity is generlly ssoited with high intke of junk foods rih in energy, ft, sugr nd slt omined with dysfuntionl ontrol of ppetite nd lk of exerise. There is some evidene to suggest tht ppetite nd ody mss n e influened y mternl food intke during the fetl nd sukling life of n individul. However, the influene of mternl junk food diet during pregnny nd lttion on the feeding ehviour nd weight gin of the offspring remins lrgely unhrterised. In this study, six groups of rts were fed either rodent how lone or with junk food diet during gesttion, lttion nd/or post-wening. The dily food intkes nd ody mss were mesured in forty-two pregnnt nd ltting mothers s well s in 216 offspring from wening up to 1 weeks of ge. Results showed tht 1 week-old rts orn to mothers fed the junk food diet during gesttion nd lttion developed n exerted preferene for ftty, sugry nd slty foods t the expense of protein-rih foods when ompred with offspring fed lned how diet prior to wening or during lttion lone. Mle nd femle offspring exposed to the junk food diet throughout the study lso exhiited inresed ody weight nd BMI ompred with ll other offspring. This study shows tht mternl junk food diet during pregnny nd lttion my e n importnt ontriuting ftor in the development of oesity. Junk food: Cfeteri diet: ppetite progrmming: Feeding ehviour: Oesity Oesity nd relted disorders re on the inrese. ording to report y WHO, round one illion humn individuls were lssified s overweight worldwide in 23 nd 3 million were oese 1. Oesity ffets popultions inresingly erlier in life with round 22 million hildren under the ge of yers eing lssed s overweight. Men nd women pper to e differently ffeted, with the oesity rte eing greter in women 1. Oesity nd overweight re ssoited with rnge of disorders suh s type 2 dietes 2 nd CVD 3 nd re using inresing onerns in oth the Western nd developing worlds, essentilly euse of their impt on the eonomy nd welfre of popultions. The use of the widespred inrese in oesity nd overweight is generlly ttriuted to overeting nd, therey, the diffiulties tht some people experiene in ontrolling their ppetite, omined with lk of exerise. ppetite regultion n e even more hllenging y the undne nd esy vilility of so-lled junk foods, whih re defined s hevily proessed, highly pltle nd hyper-energeti nd re often deprived of the vitmins nd essentil nutrients found in whole unproessed foods. Beuse over-eting nd lk of exerise onstitute growing threts to helth nd onsequent eonomi reperussions, there is n inresing effort from governments worldwide to enourge helthier eting hits not only in dults ut lso in hildren 4,. However, there is lso umulting evidene tht ppetite nd tivity levels n e influened or progrmmed y mternl nutrition during the fetl nd sukling life of n individul 6 11. Most studies on ppetite progrmming hve, however, predominntly een foused on mternl undernutrition, nd the influene of mternl junk food diet on the feeding ehviour, ody weight nd tivity levels of the offspring remins lrgely unhrterised. In the present study, we hve therefore given rts d liitum ess to seletion of pltle junk foods designed for humn onsumption, s previously desried 12, in order to exmine the feeding ehviour nd food preferene of pregnnt nd ltting rts nd determine the influene of suh mternl junk food diet on ppetite regultion, food preferene, ody weight gin nd tivity levels in the offspring up to 1 weeks of ge. The im of this study is therefore to exmine whether exposure to mternl junk food diet during pregnny nd lttion n e ontriuting ftor in the development of oesity y influening the feeding ehviour, growth rte nd tivity levels in offspring. Experimentl methods nimls ll niml work ws rried out under UK Home Offie liene to omply with the nimls (Sientifi Proedures) revition: G2, gesttion dy 2. * Corresponding uthor: Stéphnie Byol, fx þ44 () 2 7388 127, emil syol@rv..uk
2 S.. Byol et l. t 1986. ll nimls used were purhsed from Chrles River, Mrgte, Kent, UK. They hd free ess to wter nd were kept in light-, temperture- nd humidityontrolled environment throughout the experiment (14 1 h light drk yles, 2 ^ 28C, 4 % reltive humidity). The nimls were fed two types of diet throughout the study. They were fed either RM3 rodent how lone d liitum (SDS Ltd, Bethworth, Surrey, UK) or with junk food diet, lso known s feteri diet 12, whih onsisted of eight different types of pltle foods, purhsed from British supermrket. The pltle food inluded isuits, mrshmllows, heese, jm doughnuts, hoolte hip muffins, utter flpjks, potto risps nd rmel/hoolte rs; desription of the nutritionl vlue nd ingredients is given in the supplementry dt file. Eh of the eight pltle foods s well s the how ws weighed efore nd 1 d fter it ws given to the rts, suh tht dily food intkes ould e lulted following orretion for humidity gin or loss. The nimls on the junk food diet reeived exess quntities of eh foodstuff inluding the how, suh tht their intke ws d liitum. Forty-two virgin femle Wistr rts ged etween 12 to 14 weeks were rndomly mted with Wistr mles in wire-ottomed ges. On the dy opultion plug ws found, the femles were isolted, fourteen femles were given the how diet nd twenty-eight were given the junk food diet s illustrted in Fig. 1. From the dy of prturition nd throughout lttion (21 d), the fourteen femles from the how group nd their offspring were mintined on the how diet (CC group), fourteen litters from the junk food diet group were swithed from the junk food to the how diet (JC group) nd the remining fourteen were mintined on the junk food diet (JJ group). On the twenty-first dy of lttion, the pups were wened. Three mles nd three femles from six litters in eh nutritionl group (216 pups in totl) were kept nd housed in groups of three silings per ge suh tht the mles were seprted from the femles. From wening up to 1 weeks of ge, the pups were either given the how or the junk food diet, suh tht there ws totl of six different dietry regimes s illustrted in Fig. 1. Therefore, thirty-six wenling pups from eh of the CC, JC nd JJ groups were wened on the how diet; these groups were nmed CCC, JCC nd JJC respetively. nother thirty-six pups from eh of the CC, JC nd JJ groups were wened on the junk food diet nd were nmed CCJ, JCJ nd JJJ respetively. Litter sizes were stndrdised y seleting those tht ontined etween ten nd sixteen pups while outsized litters were disrded from the study. Litter sizes t irth were therefore omprle nd not sttistilly different mong the six nutritionl groups (one-wy NOV). This method of stndrdising litter sizes ws fvoured over reduing litters t irth euse it enled etter stndrdistion of the numer of fetuses during gesttion, s previously desried 12. Therefore, mternl feeding ehviour during gesttion ws studied in popultion of dms tht were expeted to rry omprle numers of fetuses. Mothers nd offspring were weighed dily throughout the study exept for the dy of prturition to void using unneessry distress. The ody lengths of the offspring were mesured t the end of the experiment (1 weeks from irth), fter killing, nd were tken from the tip of the nose to the se of the til. These were used to lulte the BMI, i.e. kg/m 2. The dily post-wening growth rtes were lulted ording to the following formul: ((ody mss t dy 7) (ody mss t dy 21) / 49 d). tivity monitoring In order to determine whether differenes in ody weights ould e diretly relted to vrying levels of tivity nd voluntry exerise, unstimulted tivity levels were mesured. The mesurements were mde in some pregnnt mothers t gesttion dy 2 (G2), (ten for the how group Gesttion Chow (14) Chow (14) Lttion Post-wening Group nme Chow (36) Junk food (36) CCC CCJ Junk food (28) Chow (14) Junk food (14) Chow (36) Junk food (36) Chow (36) Junk food (36) JCC JCJ JJC JJJ Mting Birth Wening 21 d Post-ntl week 1 Fig. 1. Experimentl design. Rts were either fed rodent how lone (C) or with the junk food diet (J) during pregnny, lttion nd post-wening up to 1 weeks of ge. The numers in prentheses indite the numer of dms (gesttion), litters (lttion) nd offspring (post-wening) in eh nutritionl group. For detils of nimls nd proedures, see Experimentl methods.
Mternl junk food diet nd diet-indued oesity in offspring 3 nd sixteen for the junk food group) s well s in two mle nd two femle offspring per litter t postntl weeks 4, 6, 8 nd 1 (twenty-four nimls per group, i.e. 144 nimls in totl; the sme nimls were used throughout the study). tivity ws mesured using the Linton M13 tivity monitor nd ssoited monlite softwre (Linton Instrumenttion, Plgrve, Diss, Norfolk, UK). The monitor onsisted of two levels of IR light ems (forty-eight in totl), whih mesured tivity in X, Y, Z diretion nd ws set up suh tht the lower set of ems mesured the tivity of rts wlking t the ottom of the tnk, while the higher set mesured the tivity of rts stnding on their k legs, nmely, rering tivity. When the IR light ems were roken y the nimls movement, totl tivity ounts were reorded y the monlite softwre. tivity mesurements were performed during the light phse nd the nimls were left lone in the room while mesurements were tken in order to minimise externl visul, uditory or sented stimuli tht might hve interfered with their norml tivity. The experiments were set up suh tht the nimls were llowed to settle in the tnk for 2 min efore mesurements were reorded. The mesure of tivity ws reorded every 3 s for totl of 1 min, suh tht thirty individul mesurements were tken from eh niml in eh experiment. The sum of the totl s well s rering tivity ounts from those thirty mesurements ws then lulted nd nlysed sttistilly. Sttistil nlyses Sttistil nlyses were performed using the SPSS 14 for Windows softwre (SPSS In., Chigo, IL, US). Pregnny. pproprite rndomistion of the nimls into the six nutritionl groups t the strt of the experiment ws heked y exmining the ody mss verges nd stndrd devitions. During pregnny, there were only two types of dietry regimens, nmely, how nd junk food diet. The vriles (food, energy, mronutrient intkes, ody weights nd tivity levels) were grphilly tested for norml distriution using the explore funtion of the SPSS softwre nd nonnorml djustments were not neessry. Differenes etween these two groups were nlysed using n unpired (or independent smples ) two-tiled Student s t test together with the Levene s test for equlity of vrines to determine if equl vrines should e ssumed. Results were onsidered sttistilly signifint when P,. Lttion. During lttion, there were three types of dietry regimens, nmely, CC, JC nd JJ. The vriles (food, energy, mronutrient intkes nd ody weights) were lso grphilly tested for norml distriution nd non-norml djustments were not neessry. Differenes mong these three groups were then nlysed y one-wy NOV. When the one-wy NOV indited differenes mong the three dietry regimens (P, ), post-ho nlyses were performed to determine more speifi differenes mong the three groups. The vriles were either tested y the Tukey honestly signifintly different (HSD) or the Gmes-Howell test if the Levene s test ws P. or P, respetively. Results were onsidered sttistilly signifint when P, nd s trends when, P, 1. Post wening. fter wening, there were six different groups, nmely, CCC, CCJ, JCC, JCJ, JJC nd JJJ (Fig. 1). The vriles (food, energy, mronutrient intkes, ody weight, ody length nd relted prmeters) from the six groups were tested using hierrhil two-wy (lso known s nested ) NOV. The fixed ftors were defined s group nd sex while mother ws defined s rndom ftor. The models were designed s group, sex, mother(group) nd group sex. The residuls from these nlyses were grphilly tested for norml distriution nd the residuls were plotted ginst the predited vlues for eh prmeter to verify homogeneity of vrines. Nonnorml modifitions were not neessry. For the food intke nlyses, the hierrhil two-wy NOV showed no signifint intertion etween group sex; therefore, results were nlysed for the entire rt popultion omining mles nd femles. When the hierrhil two-wy NOV indited sttistil differenes etween group (P, ), Tukey HSD post-ho nlyses were performed to determine more speifi differenes mong the six nutritionl groups. For the results on ody mss, length, BMI nd growth rtes, the hierrhil two-wy NOV indited intertions etween group sex (P, ); therefore, the dt file ws split into sexes nd differenes mong the six nutritionl groups were nlysed independently for mles nd femles y one-wy NOV followed y post-ho nlyses when P,. The Gmes-Howell post-ho test ws used in ll ses s the Levene s test for equlity of vrines indited tht unequl vrines should e ssumed. ll results were onsidered sttistilly signifint when P, nd s trends when, P, 1. Eh post-wening growth stge ws sttistilly nlysed independently from the others nd the P vlues nd stndrd errors of the mens for the food nlyses re only represented on the grphs for week 1 for lrity. Beuse the food intkes re not lwys lerly differentited on the grphs, the men vlues nd stndrd errors of the mens for the totl energy nd energy from the junk food soure onsumed y the nimls t postntl weeks 4 nd 1 re presented in Tle 1. Results nd disussion Pregnnt dms exhiit hyperphgi nd mrked preferene for junk food over how, whih is ssoited with ody weight gin nd deresed tivity levels t gesttion dy2 Fig. 2() shows tht pregnnt dms given free ess to seletion of pltle junk foods together with their norml lned how te pproximtely 4 % more food (g) nd 6 % more energy on verge every dy ompred with those given rodent how lone (P, 1 in oth ses). Pregnnt rts fed the junk food diet exhiited mrked preferene for junk food over how with only 2 % of the totl energy onsumed throughout pregnny originting from the rodent how. Fig. 2(B) shows tht the pregnnt rts fed the junk food diet te more totl ft, inluding sturted ft, more rohydrtes, inluding surose, s well s more slt; however, they redued their protein nd dietry fire intke ompred with rts fed how lone (P, 1 in ll ses). These results lerly show tht pregnnt rts, given d liitum ess to junk food, exhiited hyperphgi hrterised y mrked preferene for foods rih in ft, surose nd slt t the expense of protein-rih foods, when ompred with rts tht only hd
4 S.. Byol et l. Tle 1. Totl energy nd energy from the junk food soure onsumed dily y the offspring during post-ntl weeks 4 nd 1* (Vlues re mens with their stndrd errors of the men) Totl energy onsumed (kj) Energy from junk food (kj) Week 4 Week 1 Week 4 Week 1 Group* Men SEM Men SEM Men SEM Men SEM CCC 187 9 3 6 399 9 29 7 CCJ 227 8 1 4 723 3 62 1 132 8 8 41 6 44 9 JCC 176 3 4 7 4 6 28 4 JCJ 194 2 3 67 2 8 112 4 6 1 6 2 1 JJC 12 9 4 2 399 4 21 9 JJJ 231 3 14 3 88 9 69 111 1 9 2 77 4 4 6,, Men vlues with different supersript letters were sttistilly different etween the six nutritionl groups (P, ). * For detils of nimls nd proedures, see Experimentl methods. ess to rodent how. lthough the ody mss of dms ws omprle mong ll groups t the strt of the experiment, the inresed energy intke in the junk food group throughout gesttion ws ompnied y n inrese in ody mss t G2 with the junk food-fed dms (438 (SEM 2) g) eing 13 % hevier thn those fed how lone (386 6 (SEM 4) g, P, 1, supplementry Tle 2, ville online). The dms inluded in the study gve irth to sttistilly omprle numers of pups, whih indites tht the inrese in ody mss ws proly not used y n inresed numer of fetuses. t G2, the mothers in the junk food group lso exhiited 27 % (P¼ 38) nd 37 % (P¼ 13) redution () 4 7 4 3 3 2 2 1 1 6 4 3 2 1 mount Energy (B) 2 2 1 1 Totl ft Sturted ft Crohydrtes Surose Proteins Fires Slt 2 18 16 14 12 1 8 6 4 2 Fig. 2. verge dily dietry intke during pregnny. Pregnnt rts fed the junk food diet (J: ) exhiit n inresed energy intke () s well s preferene for foods rih in ft, rohydrtes nd slt t the expense of protein-rih foods (B) ompred with those fed rodent how lone (C:). Results re mens with their stndrd errors of the men, n 13 for C ndn 28 for J. P, 1 y unpired two-tiled Student s t test. For detils of nimls nd proedures, see Experimentl methods.
Mternl junk food diet nd diet-indued oesity in offspring in totl nd rering tivity level respetively. Therefore, inresed energy intke omined with redued tivity my explin the inresed ody mss oserved t G2 in the feteri-fed dms. Ltting dms exhiit hyperphgi nd preferene for junk food over how ut this is not ompnied y inresed ody mss Fig. 3() shows tht the hyperphgi nd inresed intke of foods rih in ft, surose nd slt oserved during pregnny ontinued into lttion in rts kept on the junk food diet (JJ group). During lttion, 3 % of the totl energy onsumed y the JJ group originted from how. Interestingly, the dily energy intke of rts tht were swithed from the junk food diet to how lone from irth (JC group) ws redued y pproximtely 12 % (P¼ 24) ompred with those fed rodent how throughout (CC group). Consequently, the totl ft (inluding sturted ft), surose, protein, fire nd slt intkes were lso redued y pproximtely 12 % in the JC group ompred with the CC group (Fig. 3(B)). Despite onsuming more energy throughout lttion, the ody mss of mothers in the JJ group ws omprle with those in the CC nd JC groups t the end of lttion, nmely, 21 d post-prtum (CC 36 4 (SEM 8) g; JC 363 9 () (B) 1 9 8 7 6 4 3 2 1 4 4 3 3 2 2 1 1 Totl ft * Sturted ft mount Crohydrtes Surose Proteins Fires Energy 16 14 12 1 8 6 4 2 Slt.4.4.3.3.2.2.1.1. Fig. 3. verge dily dietry intke during lttion. Ltting rt dms fed the junk food diet (JJ: ) exhiit n inresed energy intke () s well s preferene for foods rih in ft, surose nd slt t the expense of proteinrih foods (B), while rts rehilitted to how diet from junk food diet during gesttion (JC: ) exhiit redued energy nd nutrient intke ( nd B) ompred with rts fed rodent how throughout (CC:). Results re mens with their stndrd errors of the men, n 14 for eh group., Men vlues with different supersript letters were sttistilly different mong the six nutritionl groups (P, ). *Indites trends, i.e.,p, 1 y onewy NOV nd post-ho nlyses. For detils of nimls nd proedures, see Experimentl methods. (SEM 7) g; JJ 349 4 (SEM 6 1) g; P¼ 14; supplementry Tle 2, ville online). The tivity levels were not mesured in ltting dms ut the lk of ody mss inrese, despite onsuming more energy, suggests tht the mothers fed the junk food diet during lttion my hve invested more energy in milk prodution nd therefore their milk my hve een riher thn tht produed y the how-fed ltting rts. In the present study, we did not mesure milk omposition; however, nother study using vrition of the junk food diet model showed tht feteri-fed dms produed milk tht ws riher in energy nd ft 13. Therefore, it is likely tht in our model, too, the dms fed the junk food diet might lso hve produed riher milk nd we propose tht this might prtly explin the lk of ody weight gin in the JJ group despite inresed energy onsumption throughout lttion. The influene of mternl junk food diet on the ody weight of offspring t irth nd t wening: similrities with the mternl low protein diet model Despite inresed mternl energy intke during pregnny nd omprle litter sizes, the offspring orn to mothers fed the junk food diet (6 26 (SEM 3) g) exhiited mrginl (4 %) ut signifint redution in irth weight ompred with those fed how lone (6 (SEM 6) g, P, 1). Similrly, t wening, the ody mss of pups from the JJ group (49 39 (SEM 7) g) remined lower ompred with those fed rodent how lone throughout, nmely, the CC group (2 8 (SEM 4) g, P, 1). Swithing from the junk food diet during gesttion to rodent how lone during lttion ws even more detrimentl for the growth of the offspring, s wenling pups from the JC groups were lighter in weight (43 92 (SEM 7) g) ompred with oth the CC nd JJ groups (P, 1 in oth ses; supplementry Tle 3). These results on offspring s ody weights t irth nd wening re in line with previous oservtions mde in our lortory using the sme feteri diet model 12. However, in the previous study, ody mss results did not reh sttistil signifine due to muh smller numers of nimls eing used. nother study using vrition of the feteri diet model 14 showed tht litter sizes were inresed, wheres irth weights were not ffeted. However, in Holemns et l s study, the feteri diet ws given to the nimls 4 weeks efore mting, while in the present study it ws given on the first dy of gesttion. The resons why the irth nd wening weights of offspring exposed to the junk food diet were redued in the present study re unler ut one explntion might e mternl protein intke. Despite inresed totl energy intke, the feteri-fed dms deresed their protein intke y pproximtely 37 % nd 34 % during gesttion nd lttion respetively. Previous reports hve shown tht isoenergeti ut % nd 6 % protein-restrited diets throughout pregnny indued redution in the offspring s irth weights 1,16. In the urrent study, the voluntry protein restrition (37 %) during gesttion ws not s severe s % nd 6 % nd the redution in irth weight oserved (4 %) ws lso less severe thn the reported 9 % nd 17 % redution ssoited with % nd 6 % protein redution respetively 1,16. Similrly, 6 % protein restrition during oth gesttion nd lttion led to 2 % redution in ody
6 S.. Byol et l. weight t wening 16, whih is lso onsistent with the present results, showing 7 % redution in ody mss t wening in pups from the JJ group ompred with the CC group. In light of this, it thus ppers tht the voluntry redution in protein intke during gesttion nd lttion in feteri-fed dms my e key ftor in explining the redued irth nd wening weights oserved nd tht mternl protein intke rther thn overll energy intke my ply mjor role in regulting the offspring s ody mss t irth nd t wening. However, protein intke lone does not explin why the wening weight of pups from the JC groups ws lower ompred with oth the CC nd JJ groups, s the protein intke during lttion in this group ws greter thn in the JJ group. It thus ppers tht inresing protein intke during lttion ws not suffiient to restore norml ody mss in wenling pups exposed to the junk food diet during their fetl life. mternl junk food diet efore wening promotes n exerted preferene for junk food nd leds to greter propensity for oesity in the offspring The min fous of the present study ws to exmine whether mternl junk food diet during pregnny nd lttion ould influene the long-term feeding ehviour, growth rte nd tivity levels of offspring. Results in Fig. 4() nd Tle 1 show tht t postntl week 1, the rts wened on junk food, nmely, the CCJ, JCJ nd JJJ groups, inresed their energy intke ompred with those wened on rodent how lone, nmely, the CCC, JCC nd JJC groups. However, rts exposed to the junk food diet during gesttion nd lttion (JJJ group) exhiited n pproximtely 18 % nd 26 % dily inrese in energy intke ompred with other offspring wened on junk food, ut whih were fed rodent how lone during oth gesttion nd lttion (CCJ group) or during lttion lone (JCJ group), (P, 1 in oth ses).we further hrterised the soure of energy intke in junk food diet-fed rts nd results in Fig. 4(B) show tht the energy intke from how ws omprle in ll offspring wened on the junk food diet, nmely, CCJ, JCJ nd JJJ groups. However, Fig. 4(C) shows tht the energy intke from the junk food soure ws inresed in the JJJ group ompred with the CCJ nd JCJ groups (P, 1 for oth ses). Further nlyses showed tht the exerted intke of junk food in the JJJ group ws hrterised y seletive preferene for foods rih in ft, sugr nd slt ut not in proteins nd fires (supplementry Fig. 2). Therefore, lthough ll young rt offspring enjoyed eting junk food nd fvoured it over how, prtiulrly during the ltest stges of growth exmined (Fig. 4(D)), the nimls tht were exposed to the junk food diet during pregnny nd lttion (JJJ group) exhiited exerted hyperphgi nd greter preferene for junk food ompred with offspring fed lned how diet prior to wening (CCJ group) or during lttion (JCJ group). It is importnt to note tht offspring exposed to the junk food diet during gesttion lone (JCC group) or during gesttion nd lttion (JJC group) nd were then wened on how did not exhiit hyperphgi (Fig. 4()). Pups from the JJC group exhiited redution in energy intke for the first 2 weeks from wening ompred with oth CCC nd JJJ groups (Fig. 4, Tle 1), inditing tht removing ess to the pltle food t wening indued temporry redution in energy intke, whih then returned to ontrol levels y week 1. () 12 1 8 6 4 2 Totl energy,, 4 6 7 8 9 1 Weeks fter irth (B) 4 3 2 1 4 Energy from how 6 7 8 Weeks fter irth 9,,,, 1 (C) 9 8 7 6 4 3 2 1 Energy from junk food,,, 4 6 7 8 9 1 Weeks fter irth Soure of energy onsumed (D) 1 Perentge 8 6 4 2 4 6 8 1 4 6 8 1 4 6 8 1 Weeks fter irth CCJ JCJ JJJ Fig. 4. verge dily energy intke for postntl weeks 4 to 1. Offspring exposed to the junk food diet (JJJ) throughout the study exhiit exerted hyperphgi () nd n inresed tste for junk food (B, C nd D). Open symols indite nimls wened on how lone while filled symols indite those wened on junk food: CCC +; CCJ X; JCCD; JCJO; JJC ; JJJ B; energy from how ; energy from CD B.,, Different letters t week 1 indite sttistil differenes mong the six nutritionl groups (P, ) y hierrhil two-wy NOV followed y Tukey honestly signifintly different (HSD) post-ho nlyses. For detils of nimls nd proedures, see Experimentl methods.
Mternl junk food diet nd diet-indued oesity in offspring 7 To exmine whether energy intke in offspring ould e diretly influened y vrition in tivity level, we mesured tivity levels during the light phse over 1 min period t postntl weeks 4, 6, 8 nd 1. Results showed tht the six dietry regimens exmined did not influene the totl nd rering tivity levels in the offspring, whether mles or femles (dt not shown). Therefore, we found no evidene tht the six dietry regimens influened tivity levels suh tht it might e the predominnt explntion for the inresed energy intke in feteri-fed rts. However, full hrteristion of the nimls tivity inluding noturnl tivity, whih is when rts re normlly more tive, over longer period, is required to fully eliminte tivity s signifint ftor explining the inresed energy intke. We lso noted lrge vritions in tivity levels in femle offspring nd feel tht this might e used y differenes in ovultion sttus. Femle rts ppered to shiver nd e hypertive when ovulting. Therefore, for future tivity monitoring experiments, it might e enefiil to tke into ount the ovultion sttus of femle rts to void suh vriility, whih my msk the true effets of the tretment. The inresed energy intke in the JJJ group over ll other groups ws ompnied y n inrese in ody mss, BMI nd post-wening growth rtes in oth mle nd femle offspring t week 1 (Fig. (),(B),(D)), even though JJ offspring exhiited lower ody mss t wening ompred with CC offspring. The inresed ody mss nd BMI in the JJJ group ompred with the CCC group were greter in femles (32 % nd 21 % respetively) thn in mles (22 % nd 18 % respetively). This indites tht femles were more prone to weight gin thn mles when exposed to junk food diet throughout the study. Fig. (C) lso shows tht the dietry regimens exmined did not influene the ody length of mle offspring. However, junk food diet throughout the study (JJJ group) or fter wening (CCJ group) indued n inrese in ody length in femle offspring (Fig. (C)). Results in Fig. () lso show tht despite eing hevier t wening, pups in the CCJ group were 1 % nd 18 % lighter thn mles nd femles from the JJJ group respetively t week 1 (P¼ 12 nd P¼ 19 for mles nd femles respetively). Surprisingly, mles from the CCJ group were not sttistilly hevier thn the mles from the CCC group; however, their BMI ws greter (Fig. (),(B)). On the ontrry, the femles from the CCJ group were hevier thn those in the CCC group ut their BMI were omprle (Fig. (),(B)). These results therefore show tht lned diet during gesttion nd lttion n provide some protetion over junk food diet-indued oesity in offspring. Tken together the results show tht exposure to mternl junk food diet during gesttion nd lttion promotes exerted hyperphgi with seletive preferene for junk foods rih in ft, sugr nd slt, s well s overweight gin when ompred with offspring lso given free ess to junk food ut whih were exlusively fed lned how diet efore wening or during lttion lone. Is pltility the min driving stimulus for the exerted hyperphgi? The present study shows tht, like mn, rts, whether pregnnt nd ltting dms or young offspring, exhiited preferene for pltle foods rih in ft, sugr nd slt over plin yet nutritionlly lned rodent how. In ddition, when the pltle food ws removed nd the rts were given ess () 4 4 3 3 2 2 1 1 g B B Body mss CCC CCJ JCC JCJ JJC JJJ C (B) mss kg/m 2 8 E-4 7 E-4 6 E-4 E-4 4 E-4 3 E-4 2 E-4 1 E-4 E-4 B BMI CCC CCJ JCC JCJ JJC JJJ C d (C) 3 2 2 1 1 m Body length CCC CCJ JCC JCJ JJC JJJ (D) 1 9 8 7 6 4 3 2 1 B Post-wening growth rtes B B CCC CCJ JCC JCJ JJC JJJ B C Fig.. The influene of mternl junk food diet on ody mss, length nd ssoited prmeters in offspring. Mle nd femle offspring fed the junk food diet throughout the study exhiit inresed ody mss (), BMI (B) nd post-wening growth rtes (D) while ody length is only ffeted in femle offspring (C). Different pitl nd lower se letters indite sttistil differenes mong the six nutritionl groups in mle nd femle offspring respetively (P, ) y onewy NOV nd Gmes-Howell post-ho nlyses. For detils of nimls nd proedures, see Experimentl methods.
8 S.. Byol et l. to rodent how lone (JC mothers nd JJC pups), they redued their energy intke ompred with rts tht hd not een exposed to the junk food diet. This further emphsises tht pltility plys mjor role in ppetite regultion nd energy intke s previously reviewed 17. However, it is importnt to note tht similr redution in food intke hs een reported in non-pregnnt oese femle mie, whih were swithed from high-ft to stndrd how diet 18, inditing tht vritions in ft ontent lone n use redution in food intke. Nevertheless, ft ontent lone my not explin the inresed energy intke oserved in the junk food-fed rts, s it hs een reported previously tht pregnnt rts fed high-ft how diet redued their food intke (g) suh tht their gross energy intke ws omprle with ontrol group fed stndrd how diet 19. The mehnisms tht regulte ppetite re omplex nd not yet fully eluidted. ppetite regultion involves ross tlk etween ppetite entres in the rin nd peripherl ftors, suh s leptin, insulin nd ghrelin, to regulte energy lne, stiety nd hunger 2. Nevertheless, feeding is not only mtter of regulting energy lne; it is lso plesurle experiene tht involves rewrd entres in the rin, suh tht the omintion of plesure with feeding my osionlly override the norml regultion of stiety 2. More speifilly, pltle foods rih in ft nd sugr hve een shown to inhiit the stiety signls while promoting hunger nd stimulting the rewrd entres 17. One key question in the present study is wht re the underlying mehnisms driving the JJJ group to overet ompred with ll other groups? Ftors suh s tivity, ody omposition nd ody weight mintenne s well s vrying sensitivity to food pltility might ll ontriute to this. More tive rts would require more energy intke ut tivity mesurements showed no onlusive evidene tht the diets signifintly influened the rts tivity. We hve shown previously tht our junk food diet model ould influene ody omposition in wenling rts, leding to musle trophy nd inresed diposity 12. Different ody omposition my influene energy expenditure nd therey energy intke. Hevier odies might lso require more energy to sustin stedy weight nd, indeed, the rts from the JJJ group were overweight t week 1 ompred with those in ll other groups. Furthermore, exmintion of energy intke per g ody weight t week 1 showed no differenes mong the three groups wened on the junk food diet (supplementry Fig. 3()), suggesting tht sustining ody mss might lso influene the nimls food intke, prtiulrly during the lter stges of growth exmined. However, sustining ody weight is unlikely to e the min driving ftor explining the exerted hyperphgi oserved in the JJJ group, t lest immeditely fter wening, euse t wening these offspring were signifintly lighter thn those in the CCJ group nd yet the energy intke etween these two groups during the first week from wening were omprle. Furthermore, pups in the JJC group, whih were eqully underweight s those in the JJJ group t wening, did not inrese their energy intke when wened on how lone. Therefore, if sustining ody mss or thup growth were the mjor driving stimuli to explin the exerted hyperphgi oserved in the JJJ group, then the JJC pups would lso overet regrdless of their diet. Further evidene tht food pltility my e the min driving stimulus for the exerted hyperphgi oserved in the JJJ group omes from the study of the soure of energy onsumed. ll rts fed the junk food diet fter wening (CCJ, JCJ nd JJJ groups) te omprle quntities of rodent how nd the exess energy intke in rts from the JJJ group exlusively originted from the junk food soure. In ddition, these rts preferentilly seleted foods rih in ft, sugr nd slt ut not in protein, therefore rguly more pltle. This indites tht pltility s well s energy, ft, sugr nd slt ontent might e mjor driving stimulus for the exessive food intke oserved in the JJJ group. This is further supported y the feeding ehviour of nimls in the JJC group, whih were lso exposed to the junk food diet efore wening. In this group, when the pltle food, i.e. the ftor tht we suspet is promoting the exerted overeting, ws removed nd the rts were only given exlusive ess to rodent how, their energy intke ws not only redued ompred with the JJJ group ut ws lso redued ompred with the CCC group for 2 weeks from wening, efore rehing CCC levels y week 1. In our view, this indites tht food pltility ws therefore mjor driving stimulus for the exerted hyperphgi oserved in the JJJ group. In light of these, it thus ppers tht exposure to mternl junk food diet during gesttion nd lttion promotes n exerted tste for pltle foods rih in ft, sugr nd slt in the offspring. The present study therefore suggests tht exposure to mternl junk food diet during the fetl nd sukling life of n individul might e ontriuting ftor s to why some individuls might find it esier thn others to ontrol their junk food intke when given free ess to feteri-style diet. Lttion: n importnt period for the progrmming of n exerted intke of junk food It ppers tht post-wening hyperphgi n e progrmmed during the fetl life of n individul through mternl undernutrition 21 s well s during the sukling period y inresed intke of milk 22,23. The present study further emphsises tht mternl nutrition during lttion might ply key role in influening the long-term ppetite of the offspring given free ess to junk food. lthough groups CJC nd CJJ were not inluded in the study, the importne of lttion is illustrted in rts exposed to the junk food diet during gesttion nd fter wening ut not during lttion. Offspring from the JCJ group did not exhiit the long-term inresed energy intke tht ws oserved in the JJJ group (Fig. 4) nd their ody mss, BMI, ody length nd post-wening growth rtes were omprle with the CCC group. It thus ppers tht swithing to rodent how diet during lttion nd the ssoited 12 % voluntry redution in energy intke (Fig. 2) prevented the exerted hyperphgi nd overweight gin oserved in offspring fed the junk food diet throughout the study (JJJ). The importne of the sukling period for the progrmming of hyperphgi in offspring hs een previously desried in the litter size redution model 22 nd it ws suggested tht overll milk intke s well s milk omposition might e key regultors of the development nd mturtion of the entrl nd peripherl ontrol of ppetite. In the present study, we did not mesure milk omposition ut it ppers
Mternl junk food diet nd diet-indued oesity in offspring 9 tht swithing from junk food diet to how t irth might hve influened milk prodution, omposition nd/or the ltting ehviour of the dms leding to some protetion ginst the exerted hyperphgi nd overweight gin oserved in the JJJ group. Conlusions The present study shows tht rts given free ess to junk food inrese their energy intke nd spontneously exhiit preferene for ftty, sugry nd slty foods. The long-term preferene nd intke of junk food is further exerted when offspring hve een exposed to the junk food diet during pregnny nd lttion leding to greter propensity for oesity. However, omintion of mild energy restrition (12 %) nd lned diet during lttion n prevent the over-exessive onsumption of junk food nd ssoited overweight gin. It lso ppers tht food pltility might e n importnt driving stimulus for the exerted hyperphgi oserved. This study therefore emphsises tht helthy eting hits should e enourged, not only in young hildren ut lso in pregnnt nd restfeeding women, to help omt the oesity epidemi. The messge to instil in popultions is tht women my not onsider pregnny nd restfeeding s n opportunity to overindulge on ftty, sugry nd slty foods, on the misguided ssumption tht they re eting for two. Indeed, we show evidene tht mternl junk food diet might promote n exerted tste for junk food nd greter propensity for oesity in offspring, whih might in turn mke it more diffiult to enourge helthy eting hits nd therey ontrol oesity nd relted prolems. knowledgements The uthors thnk stff of the Biologil Servies Unit t the RVC, s well s Julie Dupu, Ntli Perez nd the Musle Unit for their help with the niml work. The uthors lso thnk viv Petrie for her help nd dvie with the sttistil nlyses. This work ws funded y the Wellome Trust. 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