Watch The Men Who Made Us Thin Season 1 Episode 4 Online

In the final instalment of this four-part series, Jacques Peretti asks why the world's population continues to get fatter, despite the fact that billions are spent on weight loss every year. He travels to America to investigate the parallels between food companies and the tobacco industry and meets the activists battling to introduce laws to tax fatty and sugary foods - and facing fierce resistance from industry.