I tested 3 popular fasts — sugar fasting, water fasting, and sardine fasting — for 48 hours each and tracked my ketones, glucose, mood, and energy using the KS1 from SiBio. One fast left me foggy and tired, another gave me stable energy and fat-burning ketones.

The “sugar fasting” trend is blowing up — with influencers like Mark Bell and Cole Robinson (aka the Snake Diet guy) claiming you can eat only sugar and still lose weight, feel amazing, and stay healthy. But is this just another dangerous fad… or is there actually something we can learn from it?