Came across this article today: https://www.T-Nation.com/diet-fat-loss/5-2-fat-loss-diet-for-lifters
It got me thinking.. could a person use this strategy for a lean bulk in order to keep insulin sensitivity up? Instead of a traditional bulk where you're slamming carbs and calories 7 days a week, I feel like those two 800 calorie days could actually be beneficial during a bulk, especially considering that insulin is the catalyst for muscle growth. It seems like it could be used as a way to keep your body primed to grow, instead of letting it get lazy by overfeeding it every single day.
Obviously, you'd have to consume enough calories on the other 5 days to ensure a calorie surplus at the end of the week... But I feel like manipulating insulin those two days could be important.