You might have noticed that everyone has recently become a bit obsessed with blood sugar, or glucose. Wellness firms such as ZOE here in the UK – as well as Nutrisense, Levels and Signos – claim to offer insights into how our bodies process food based on monitoring our blood glucose, among other things. But many researchers have begun to question the science behind this. To find out what we know about blood glucose levels and our health, and whether the science is nailed down on personalised nutrition, Ian Sample hears from philosopher Julian Baggini, academic dietician Dr Nicola Guess of Oxford University and ZOE’s chief scientist, and associate professor at Kings College London, Dr Sarah Berry