We conducted a pilot randomised controlled trial comparing the effects of a dietetic intervention to usual care, in 40 individuals with a body mass index >30kg/m(2) undergoing total joint replacement (TJR). The dietetic weight loss intervention comprised at least four sessions with an Accredited Practising Dietitian. At 12 months, the usual care group gained weight, +2.01kg (6.45), whereas the treatment group lost weight, -3.38kg (6.62), (p=0.015). Percentage weight change in the treatment group was -3.20% (5.24), compared to +1.67% (6.16) for the usual care group (p=0.015) and more participants in the intervention group (45%) lost ≥5% of their baseline weight (13%), (p=0.057). Physical health scores were also better for the intervention group [42.2 (11.80); 32.86 (9.91), p=0.014]. Findings suggest that a structured dietitian-led weight loss intervention in patients undergoing TJR is more effective in achieving weight loss than usual care, and can result in improved physical health scores at 12 months post-TJR.