Obesity in pregnancy increases the risk of complications for mother and child. The increasing prevalence of obesity amongst pregnant women has led to a global effort to develop interventions which are safe, and prevent development of gestational diabetes, pre-eclampsia, fetal macrosomia or delivery of a large for gestational age infant, amongst other adverse outcomes. Two approaches have been taken, pharmacological or a change in lifestyle. The focus of this talk will be on lifestyle interventions. To date, the majority have centred on recommendations which combine changes in diet and physical activity. Theoretically, these may be effective through reducing maternal insulin resistance which plays a causal role.Much of the focus has been towards restriction of gestational weight gain (GWG), a surrogate end point for clinical outcomes, as excessive GWG is associated with increased risk of complications. This approach, whilst negating the need for larger clinical trials, adequately powered for clinical outcomes, has several limitations. Meta-analysis of these studies has revealed that it is possible to achieve a modest reduction in GWG, but with little influence on clinical outcomes (Thangaratignam et al 2013). Some interventions have been underpinned with theoretical strategies designed to support behavioural change and others have not. Compliance to the intervention has infrequently been evaluated eg assessment of the change in diet or physical activity achieved. A recent systematic review of the methodologies used concluded that motivational interviewing and behavioural self monitoring are likely to be key factors in achieving limitation of GWG (Hill, Skouteris et al. 2013). The LIMIT trial was the first adequately powered lifestyle intervention RCT for obese and overweight pregnant women to address clinical endpoints (Dodd, Turnbull et al. 2014). Dietary advice incorporated food exchanges, increased fibre and fruit consumption and reduction of refined sugars. The primary outcome of a reduction in incidence of delivery of a large for gestational age infant was not met, but there was a reduction in risk for the secondary outcome of macrosomia in the intervention group (15% v 19%, RR 0.83, [95% CI 0.68 to 0.99], p=0.04). The UK UPBEAT randomised controlled trial (Poston et al, 2014) has recently finished recruitment, and will report in 2015. Here the intervention, more intense than most, focused on reducing the dietary glycemic load and increasing physical activity. In summary, there is to date no proven lifestyle intervention which can be recommended in the antenatal care of obese pregnant women.