I know because I've done Medifast. When I did it the keto sticks always turned a color even eating up to 100g a day. It was the stupidly low calories that drove me into ketosis. There's no magic to it.If you are losing weight on medifast at 900 calories a day it has exactly NOTHING to do with avoiding fruit, carbs or anything else and everything to do with calorie restriction.
I don't experience intense cravings anymore but when I did feeding them never worked. It only made things worse. Some people have their sugar dragon is a firm choke hold and are totally in control but others are the ones in the choke hold! If this is you you know who you are! If you've never had intense sweet cravings that practically ran your life you won't understand what I'm talking about. I have and I'm free of them and I'm not doing anything to jeopardize that. I don't have to. There are plenty of healthy natural whole foods that nourish my body without releasing the sugar dragon.I don't know, I don't count eating fruit (or starchy veggies) as satisfying an "unhealthy" craving for sugar. Usually it's a response to a need for some energy or a desire for something "fresh". It's more like "hey, you need more gas in your tank". An unhealthy sugar craving to me is "OMG I NEED CANDY NOW" (that never happens anymore) or thinking for 3 days about a piece of cake (it happens on occasion- paleo mug cake does the trick). I generally want fruit more on the morning after I work out, or after a day when I don't eat a lot of carbs.