[BBC] Two gadgets that analyse the gases in people's breath in an effort to reveal how they should improve their diet are being showcased at the CES tech show in Las Vegas.Lumen and FoodMarble are both pocket-sized devices that users blow into.
They each pair with a smartphone app that tells people how well they are digesting food or burning calories.
But one expert said such technology has yet to be properly validated by scientists.
Lumen has raised almost $2m (£1.57m) on the crowdfunding site Indiegogo. It has designed an inhaler-shaped product that measures carbon dioxide levels in the user's breath.
The firm says this provides a way of monitoring a person's metabolism - the chemical processes that, among other things, convert food into energy.
"You don't need to guess how much sugar was in that kung pao chicken or how many calories you did on that run," explained founder Dror Cedar.
Instead, he told the BBC, the app simply explains whether the user is burning carbs or fat. It then suggests recipes that help burn fat and, over time, Lumen learns what diet is most appropriate for each user.
