More so carbohydrate timing. For example:
IIFYM allows the ability to eat your entire allotment of carbohydrates in one sitting for that day. Let's say you do that in poptarts. If you're at ~200g carbs a day, that's about 6 poptarts more or less which is then 105g of sugar for that one meal. That's an absurd insulin spike. Do that in and out, will eventually create insulin resistance and potentially more serious ish. If you do that first thing in the morning and then have no carbohydrates left in your daily allotment to replenish your glycogen stores after a training session, your muscle tissue will deteriorate rather than grow. The anabolic window might be dead as proven by science, but an ample amount of carbohydrates and proteins within a 3~4 window on either end of your workout will still make a difference. As far as studies, I don't have any to back this example. And again, volumetrics. Blow your entire caloric/macro load in one sitting, you're gonna be real hungry the rest of the day.