A shift towards healthier diets is expected to address the challenge of providing food security and nutrition for a growing global population. This report explores whether such a shift would also have positive effects on the other two challenges food systems face: supporting livelihoods for those working along the food supply chain and contributing to environmental sustainability. The report finds that aligning diets with World Health Organisation guidelines on sugar and fat consumption would have the expected positive effect on nutrition and food security, and would also positively affect environmental sustainability. The effect on livelihoods along the food value chain, however, would overall be negative. The magnitude of the trade-offs and synergies are greater when fat consumption is reduced, as opposed to sugar consumption, because actual consumption levels of fat are further away from WHO recommendations.