How much food is the “right” amount - and why is it so hard to work that out?

Ruth Alexander explores the world of portion sizes, starting with the rise of “portion distortion” in the United States, where supersized sodas and giant restaurant plates became the norm. Nutritionist Lisa Young explains how this shift happened, and what it’s meant for public health.

In São Paulo, dietitian Marle Alvarenga shares new research comparing Brazil, France, and the US, revealing how culture and globalisation shape what feels like a normal portion. Why are French plates so much smaller - and meals so much slower - than in Brazil or America?

And psychologist Lenny Vartanian in Sydney explains the powerful pull of portion size on our behaviour: why bigger servings make us eat more, even when we know better, and why education alone isn’t enough to change our habits.

If you would like to get in touch with the show, please email: thefoodchain@bbc.co.uk

Producer: Izzy Greenfield

Photo: Three spoons showing different portion sizes (credit: getty)