It’s fluids. I’m willing to bet you’re drinking more than a liter a day. Don’t drink more SJ; drink less. And rest assured, if you’re fasting, you ARE losing body fat (even if you’re not losing weight).
It’s just 4 days, my unasked opinion probably but no need to freak out over a few days of plateau. If you said a few weeks, I would get it. Let your body do its own thing. You know you are not eating, so why panic? That’s just unnecessary stress hormone for your body. Believe in Yourself 💪