Allow me to illustrate the point using an experiment I call the "Eating Too Many Chicken McNuggets To Ruin Your Blood Sugar And The Rest Of Your Day" experiment.
A box of 20 nuggets is 320g and has 48g carb, 50g protein, 64g fat. Notice that's a helluvalottava lotta fat.
Using a handy bolus ratio and pens, wack on 48g carb worth of insulin and to be safe also dose for the 50g protein (1/3 of it my case - this is well tested, I go hypo without fail if I dose higher than 1/3).
Retire to a safe distance and simmer for 4 hours. Resulting blood sugar - 17.4 mmol/L. (Needless to say it was a shiny, showroom-new 6.0 mmol/L at the start of the experiment).
I think that's pretty conclusive proof of a powerful transient "carb intolerance" ( * ) effect from dietary fat. Apart from all that namby pamby **** about repeatability, prior hypothesis, controlled conditions, blind placebos, yadda yadda.
Please note: No alcoholic degenerate defrocked elder priests were harmed during this experiment. Much.
( * ) go on, try and get me to say "insulin resistance". I double-dares ya, ya gob**ite!)