The study of host microbe interactions is hampered by the complexity and inter-individual variability of the human gut microbiota. Therefore, a simplified human intestinal microbiota (SIHUMI) consisting of seven bacterial species was introduced into germfree rats. Species selection was based on numerical importance and fermentative abilities in the human gut. Association of the rats with the SIHUMI (Anaerostipes caccae, Bacteroides thetaiotaomicron, Bifidobacterium longum, Blautia producta, Clostridium ramosum, Escherichia coli and Lactobacillus plantarum) resulted in increased faecal concentrations of short chain fatty acids compared to germfree animals. Since the faecal butyrate concentration was low (0.9 ± 0.5 µmol/g dry matter) the SIHUMI was complemented with Clostridium butyricum. This extended bacterial community (SIHUMIx) led to an increased faecal butyrate concentration of 1.5 ± 0.7 µmol/g dry matter. Besides forming SCFA, the SIHUMIx was capable of degrading mucins, β-aspartylglycine and bilirubin. These features are characteristic of conventional animals but not observed in germfree animals. Dietary interventions with modifications in fibre and fat content led to changes in the proportion of community members. The relative increase of one member of this community in response to a high-fat diet reflects the situation reported for obese mice and human subjects. The strength of the model communities is their remarkable stability over time and their easy transfer to the offspring.

BackgroundExcessive gestational weight gain (GWG) leads to obstetric complications, maternal postpartum weight retention and an increased risk of offspring obesity. The GeliS study examines the effect of a lifestyle intervention during pregnancy on the proportion of women with excessive GWG and pregnancy and obstetric complications, as well as the long-term risk of maternal and infant obesity.MethodsThe GeliS study is a cluster-randomised multicentre controlled trial including 2286 women with a pre-pregnancy BMI between 18.5 and 40.0 kg/m2 recruited from gynaecological and midwifery practices prior to the end of the 12th week of gestation in five Bavarian regions. In the intervention regions, four lifestyle counselling sessions covering a balanced healthy diet, regular physical activity and self-monitoring of weight gain were performed by trained healthcare providers alongside routine pre- and postnatal practice visits. In the control regions, leaflets with general recommendations for a healthy lifestyle during pregnancy were provided.ResultsThe intervention did not result in a significant reduction of women showing excessive GWG (adjusted OR 0.95, 95% CI 0.66–1.38, p = 0.789), with 45.1% and 45.7% of women in the intervention and control groups, respectively, gaining weight above the Institute of Medicine recommendations. Gestational diabetes mellitus was diagnosed in 10.8% and 11.1% of women in the intervention and control groups, respectively (p = 0.622). Mean birth weight and length were slightly lower in the intervention group (3313 ± 536 g vs. 3363 ± 498 g, p = 0.020; 51.1 ± 2.7 cm vs. 51.6 ± 2.5 cm, p = 0.001).ConclusionIn the setting of routine prenatal care, lifestyle advice given by trained healthcare providers was not successful in limiting GWG and pregnancy complications. Nevertheless, the potential long-term effects of the intervention remain to be assessed.Trial registrationNCT01958307, ClinicalTrials.gov, retrospectively registered October 9, 2013.Electronic supplementary materialThe online version of this article (10.1186/s12916-018-1235-z) contains supplementary material, which is available to authorized users.

BackgroundRecent studies suggest that excessive gestational weight gain (GWG) leads to adverse maternal and fetal outcomes including weight retention in the mother and an increased risk of childhood obesity in the offspring.The aim of the GeliS study is to examine the effect of a lifestyle intervention programme during pregnancy to avoid excessive GWG and, hence, to reduce pregnancy and obstetric complications as well as the risk of maternal and offspring obesity.Methods and designThe GeliS study is a multicentre cluster-randomized controlled trial. A total number of 2500 pregnant women (singleton pregnancy) with a pre-pregnancy BMI ≥ 18.5 kg/m2 and ≤ 40 kg/m2 will be recruited in practices of gynaecologists and midwives in ten Bavarian regions. The intervention comprises three structured and individualised counselling sessions on a healthy diet, regular physical activity as well as weight monitoring during pregnancy and one session after delivery, respectively. The counselling sessions are attached to routine pre- and postnatal visits using standardised materials and procedures. In the control regions, general recommendations for a healthy lifestyle are given. An oral glucose tolerance test is offered to all participants.The primary outcome is the proportion of participants with excessive GWG. Secondary outcomes include pregnancy and obstetric complications such as frequency of gestational diabetes, preeclampsia and caesarean sections as well as weight retention in the mothers and BMI and other health variables in the offspring. A 5-year follow-up of both mothers and their infants is planned.DiscussionThe GeliS lifestyle intervention programme has been adapted to the existing routine health care system for pregnant women. If shown to be effective, it could be immediately implemented in routine care.Trial registrationThe study protocol is registered at the ClinicalTrials.gov Protocol Registration System (NCT01958307).