84 M. Pickford

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Elucidating how diet drives gutbacterial composition throughcomputational simulation

Mark Read ∗, Andrew Holmes

The University of Sydney,Darlington, NSW, Australia

A growing body of evidence has highlighted theinfluence of the gut microbial community on hosthealth, with dysbiosis being implicated in diseasesas diverse as autism, obesity and colitis. Character-isation of the mechanisms through which the gutmicrobiota and the hot interact is required to buildan understanding of how to effectively manage andmanipulate host health. This work employs com-putational simulation to elucidate the influence ofdiet composition and feeding regimen on gut bac-terial community composition.

This modelling work builds on a real mousestudy in which 250 mice were administered oneof 30 diets. Each diet consists of different ratiosof carbohydrate, protein and fat, and in addi-tion, varying quantities of cellulose that adjustthe host-accessible nutrient density of the diet.We simulate each mouse in this study, and assesshow the diet composition and varying lengths andregularities of feeding versus diet periods drivebacterial community composition. Our simulationexplicitly represents individual bacteria as belong-ing to one of five functional guilds, defined bytheir preferential access to carbon and nitrogenfrom a subset of feed-derived protein, cornstarch,dyetrose, or intestinal mucin. We simulate hetero-geneous bacterial communities, where individualbacteria compete for limited nutrient resources,have varying growth and death rates, and undergoa stress response in response to periods of nutrientscarcity.

Through simulation we can predict how differ-ent diets, the periods at which food is eaten,and periods of fasting can influence bacterial com-munity composition. We find that periodic caloricrestriction drives a greater relative abundance ofbacterial guilds that preferentially access carbonand nitrogen from mucin, and that the benefit tothese guilds varies with host diet composition. Wecan assess the quantities and times at which fibresupplements can be administered to achieve opti-mal effect in manipulating bacterial communitycomposition.

http://dx.doi.org/10.1016/j.orcp.2014.10.152

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Weight loss via the telephone —Does it work? A systematic reviewand meta-analysis

Marina M. Reeves ∗, Charlotte L.Brakenridge, Megan E. Whelan,Elizabeth G. Eakin

Cancer Prevention Research Centre,The University of Queensland,Brisbane, Australia

Introduction: Weight loss interventions aretraditionally delivered face-to-face. Telephonedelivery may overcome some barriers to acces-sing face-to-face programs and provide a usefuldelivery modality, being ubiquitous, easy to accessregardless of geographic location and suitable forlong-term contact. We systematically reviewedthe evidence on the effectiveness of telephone-delivered weight loss interventions (comparedto control and face-to-face) in overweight andobese adults. Initial weight loss interventions andextended care interventions for weight loss main-tenance were included.

Methods: A structured search of six databaseswas conducted for articles published until May2013. Included studies were randomised trialsevaluating interventions in adults with the pri-mary aim to achieve weight loss (or weight lossmaintenance) and with at least 50% of inter-vention contacts in one of the study groupsdelivered via telephone. Two investigators indepen-dently reviewed search results for eligible studiesand extracted data. Meta-analyses were by fixedeffects when studies were homogeneous or randomeffects (DerSimonian-Laird) when heterogeneitywas present.

Results: 23 studies involving 7321 participantswere eligible. Eighteen studies (5009 partici-pants) evaluating initial weight loss interventionsreported telephone versus control (or brief inter-vention) comparisons of weight loss (kg). Randomeffects models showed a significant benefit of tele-phone over control (weighted mean difference[95%CI]: −2.50 [−3.35, −1.65] kg). Five stud-ies (1059 participants) compared telephone withface-to-face intervention, with equivalent con-tact in each modality. Meta-analysis revealed nosignificant difference between modalities for ini-tial weight loss (telephone—face-to-face: −0.77[−1.77, 0.23] kg). Three studies (1610 participants)evaluating extended care interventions reportedtelephone versus brief intervention comparisons ofweight loss maintenance (kg). Random effects mod-

Annual Scientific Meeting 85

els showed significantly less weight regain with thetelephone versus brief intervention: −1.68 [−2.39,−0.96] kg.

Conclusions: Evidence suggests that telephone-delivered weight loss interventions are effectiveand can achieve similar weight loss outcomes asthose delivered face-to-face. Comparative cost-effectiveness studies are needed.

http://dx.doi.org/10.1016/j.orcp.2014.10.154

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Is the banning of unhealthy foods atschool canteens associated withprincipal influence or school policy?

Kathryn Reilly ∗, Rebecca Wyse,Serene Yoong, Nicole Nathan

Hunter New England PopulationHealth, Wallsend, NSW, Australia

Background: Poor diet is a contributing fac-tor to the high prevalence of overweight andobesity among Australian school children [1].Interventions targeting school canteens have thepotential to positively influence children’s diets[2]. Although government policies have been devel-oped to restrict the sale of unhealthy foods, theimplementation of such policies has been limited[3]. To date, most implementation support hasbeen targeted towards canteen managers. How-ever, engaging principals may also be important inoptimising policy implementation. This study aimedto investigate whether the exclusion of ‘red’ fooditems on canteen menus is associated with a highdegree of principal influence or having a schoolnutrition policy.

Method: Primary school principals in the HunterNew England region, NSW participated in a tele-phone survey. The NSW Healthy Schools Canteenpolicy uses a traffic light system to categorise foods.Foods classified as ‘red’ are prohibited for sale.Principals were asked to identify foods usually soldin their canteen from a standard list which includedcommon ‘red’ foods. They were then asked torate their perceived influence over canteen menusand whether they had a school nutrition policy.Chi-square tests were conducted to determine sig-nificant associations with ‘excluding red items’.

Results: Of the 413 principals contacted tocomplete the survey 340 (82%) consented and 276(67%) had an operational canteen. The exclusionof red foods from canteen menus was significantlyassociated with: principals having a high degree ofinfluence on canteen menus (p < 0.01), and having

a school nutrition policy that supports The NSWHealthy Schools Canteen policy (p < 0.02).

Discussion: These results suggest that Principalinfluence and supportive school policy are impor-tant factors in canteens restricting the sale ofunhealthy food items and complying with govern-ment canteen policy. Therefore it is suggested thatinterventions should engage school principals andencourage the development of school-based policy.

References

[1] Summerbell CD, Waters E, Edmunds L, Kelly SAM, Brown T,Campbell KJ. Interventions for preventing obesity in chil-dren. Cochrane Database Syst Rev 2005;3(3).

[2] Bell A, Swinburn BA. School canteens: using ripples to createa wave of healthy eating. Med J Aust 2005;183(1):5—6.

[3] de Silva-Sanigorski A, Breheny T, Jones L, Lacy K, KremerP, Carpenter L, et al. Government food service policies andguidelines do not create healthy school canteens. Aust N Z JPublic Health 2011;35(April (2)):117—21.

http://dx.doi.org/10.1016/j.orcp.2014.10.155

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The neuro-endocrinology of eating

Hendrik Rensburg

The Rensburg Clinic, Nedlands,Australia

All of the current neurobiological models offeeding behaviour are either implicitly or explic-itly founded in a homeostatic/negative feedbackphilosophy. On closer examination it appears thatthese models set the trend in current thinking, butare in many ways flawed since it relies on this home-ostatic/negative feedback as the basis for researchand understanding. A more lateral approach andbetter understanding are called for to understandthis complex system without the constraints of thistheory, which borders at times on dogma. It isargued that normal expected homeostatic mecha-nisms do not apply to the over consumption of food,but only to the under consumption of food, whichis an important survival strategy in an erratic foodsupply situation. The first obstacle is that the sys-tem that causes eating behaviour has never beennamed or even properly identified, while other sys-tems in the body has been recognized and named,even without a full understanding of its biology andphysiology. Extensive fragmented research has goneinto the ‘‘eating system’’, but because it was notidentified and named it remained largely mysteri-ous, which attracted large numbers of psychologistswho made it even more enigmatic. This system thatinitiates eating behaviour is identified as a ded-