Gestational diabetes mellitus (GDM), a common pregnancy complication, continues to be a significant public health and clinical problem. It carries significant short-term and long-term adverse health outcomes for both mother and offspring, which reinforces the significance of understanding risk factors, in particular modifiable factors, for GDM and of preventing the condition. Research in the past decade from observational studies has identified a few diet and lifestyle factors that are associated with GDM risk and demonstrated that time frames both before and during pregnancy may be relevant to the development of GDM. Findings from intervention studies on the effect of diet and lifestyle on the prevention of GDM have been largely controversial and inconsistent. Variations in study population, types of intervention, timing and duration of intervention and diagnostic criteria for GDM may all at least partly account for the large heterogeneity in the findings from these intervention studies. This review provides an overview of emerging diet, lifestyle, and other factors that may help to prevent GDM, and the challenges associated with prevention. It also discusses major methodological concerns about the available epidemiological studies on GDM risk factors. Findings from both observational and intervention studies are discussed. This review summarises a presentation given at the ‘Gestational diabetes: what’s up?’ symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Peter Damm and Colleagues, DOI: 10.1007/s00125-016-3985-5, and by Marja Vääräsmäki, DOI: 10.1007/s00125-016-3976-6) and an overview by the Session Chair, Kerstin Berntorp (DOI: 10.1007/s00125-016-3975-7).

Chemosensory problems challenge health through diminished ability to detect warning odors, consume a healthy diet, and maintain quality of life. We examined the prevalence and associated risk factors of self-reported chemosensory alterations in 3603 community-dwelling adults (aged 40+ years), from the nationally representative, US National Health and Nutrition Examination Survey (NHANES) 2011–2012. In this new NHANES component, technicians surveyed adults in the home about perceived smell and taste problems, distortions, and diminished abilities since age 25 (termed “alterations”), and chemosensory-related health risks and behaviors. The prevalence of self-reported smell alteration was 23%, including phantosmia at 6%; taste was 19%, including dysgeusia at 5%. Prevalence rates increased progressively with age, highest in those aged 80+ years (smell, 32%; taste, 27%). In multivariable logistic regression, controlling for sociodemographics, health behaviors, and chemosensory-related conditions, the strongest independent risk factor for smell alteration was sinonasal symptoms (odds ratio [OR] = 2.06; 95% confidence interval [CI]: 1.63–2.61), followed by heavy drinking, loss of consciousness from head injury, family income ≤110% poverty threshold, and xerostomia. For taste, the strongest risk factor was xerostomia (OR = 2.65; 95% CI: 1.97–3.56), followed by nose/facial injury, lower educational attainment, and fair/poor health. Self-reported chemosensory alterations are prevalent in US adults, supporting increased attention to decreasing their modifiable risks, managing safety/health consequences, and expanding chemosensory screening/testing and treatments.

Aims/hypothesis Depression and glucose intolerance commonly co-occur among non-pregnant individuals; however, the temporal relationship between gestational diabetes (GDM) and depression during pregnancy and the postpartum period is less understood. Our objective was to assess longitudinal associations between depression early in pregnancy and GDM risk, as well as GDM and subsequent risk of postpartum depression. Methods Data came from the prospective National Institute of Child Health and Human Development Fetal Growth Studies-Singleton cohort (2009–2013), and had been collected at 12 US clinical centres. Pregnant women without psychiatric disorders, diabetes or other chronic conditions before pregnancy were followed throughout pregnancy (n = 2477). Only women with GDM and matched controls were followed up at 6 weeks postpartum (n = 162). GDM was ascertained by a review of the medical records. Depression was assessed in the first (8–13 gestational weeks) and second (16–22 weeks) trimesters and at 6 weeks postpartum using the Edinburgh Postnatal Depression Scale. Postpartum depression was defined as a depressive symptom score ≥10 or antidepressant medicine use after delivery. RR and 95% CI were adjusted for pre-pregnancy BMI and other risk factors. GDM was considered to be the outcome for the first set of analyses, with depression in the first and second trimesters as the exposures. Postpartum depression was considered as the outcome for the second set of analyses, with GDM as the exposure. Results Overall, comparing the highest and lowest quartiles of first-trimester depression scores, the scores from the highest quartile were associated with a significant twofold (95% CI 1.06, 3.78) increased risk of GDM, but this was attenuated to 1.72-fold (95% CI 0.92, 3.23) after adjustment; the second-trimester results were similar. The risk was stronger and significant in both trimesters among non-obese women (p for trend 0.02 and 0.01, respectively), but null for obese women. Women with persistently high depression scores in both trimesters had the greatest risk of GDM (highest vs lowest quartile in both trimesters: adjusted RR 3.21, 95% CI 1.00, 10.28). GDM was associated with an adjusted 4.62-fold (95% CI 1.26, 16.98) increased risk of subsequent postpartum depression. Conclusions/interpretation This prospective study demonstrates a modest association between depressive symptoms early in pregnancy and an increased risk of incident GDM, as well as between GDM and subsequent postpartum depression risk, highlighting pregnancy and the postpartum period as an important susceptible time window during the life course for the interplay between depression and glucose intolerance phenotypes. GDM risk associated with elevated depressive symptoms was particularly high among non-obese women and women with symptoms persisting across the first two trimesters of pregnancy.