Michael Blastland asks if it's desk-bound work, rather than over-eating, which is making more and more of us obese. He hears about remarkable research which, despite received wisdom, suggests that people in the UK have reduced their calorie intake. However, they are expending far less physical energy, particularly because of new patterns of work which now require little if any bodily exertion. Michael examines projects to change individual behaviour such as corporate wellness programmes and altering office layouts - but finds it's going to be a tough sell.

Interviewees:

Dr Melanie Lührmann, Senior Lecturer, Royal HollowayProfessor Alexi Marmot, architect, UCLProfessor Andre Spicer, Cass Business School Professor Mike Kelly, School of Clinical Medicine, Cambridge University

Producers: Estelle Doyle, Phoebe Keane and Smita Patel.