High consumption of sugar-sweetened beverages (SSBs) is acknowledged as a risk factor for weight gain and metabolic disease. A common strategy for reducing this risk is to switch from consumption of SSBs to ‘diet’ beverages containing non-nutritive sweeteners (NNS). However, research on the effects of NNS is mixed: While a majority of studies indicate no harm, some animal and cross-sectional data suggest NNS confer increased risk of metabolic disease. The present experiment modelled whether the switch from SSB to NNS beverages described above conferred positive outcomes on behavioural and metabolic measures. Thus, in Stage 1, thirty adult female rats received ad-libitum access to 10% sucrose solution in addition to chow and water for 4 weeks. In Stage 2, rats were switched either to 0.1% Saccharin (Suc-Sacch) or to Water (Suc-Water) or remained on 10% Sucrose (Suc-Suc) for a further 4 weeks. Weight gain in Stage 2 was reduced for Suc-Sacch and Suc-Water groups relative to the Suc-Suc group. At cull, the Suc-Suc group showed poorer insulin sensitivity and greater g/kg fat than Suc-Water and Suc-Sacch groups. There were no group differences in either fasting glucose or liver and plasma triglyceride content. Short-term recognition memory, assessed using the place/object task, found no group differences but poorer performance overall on the hippocampal-dependent place task, consistent with all rats’ access to sucrose in Stage 1. These results show beneficial effects on weight gain, insulin resistance and adiposity after switching from Sucrose to either Saccharin or Water. Our and others’ past research suggests that Stage 2 may have been too short to observe group differences on other measures.