On this episode we review a product that Darren recently started using called the Lumen. Lumen is a device that claims to be able to monitor your metabolism by measuring the concentration of CO2 and O2 in your breath. Darren originally discovered and backed this product on the crowdfunding site, Indiegogo back in July of 2018. Nineteen months, he received the device and shares his first impressions of it after using it for two weeks.