Introduction Brazil and Mexico are two of the fastest growing economies in the world. Mexico currently has one of the largest prevalence's of obesity in the world 24.2% for men and 34.5% for women in 2006 while Brazil has much lower levels of 8.9% and 13.1% (2003 figures). What will be the future impact of these trends particularly for their respective healthcare systems.

Methods Utilising the method developed for the Foresight Tackling Obesities study in the UK. The authors firstly predict future trends based on current data and then by feeding those into a micro-simulation programme developed by the NHF calculate future attributable disease burdens and their attendant health costs based on these trends and is able to test various future scenarios.

Results If unchecked the rates of increase of obesity in Mexico, will mean it faces an unsustainable attributable disease burdens and attendant health costs. If significant policies are enacted to ameliorate these trends then even relatively small population reductions in BMI could have significant health benefits to the population. Brazil though lagging behind could soon have unsustainable obesity levels too if nothing is done. The example of Mexico should offer a wake up call for Brazilian health policy makers and others in the region as to what the future impact of ignoring a rise in obesity trends will be.

Conclusion As yet there is little evidence of the effectiveness of national policies to stem the rise in obesity but this study shows even small population changes can have substantial savings to a countries future healthcare costs.