Are dietary fats, saturated fats bad?

No.

Dietary fats are critical in recovery and shooting for 45% percent of your daily intake coming from fats (saturated equally critical) helps with specific healing requirements.

Myelin is a fatty covering on nerves that allows for fast and accurate conductance of electric signals. Not all nerves in our nervous system are myelinated, but those that are need to be for us to function well.

During starvation your body uses the myelin on your nerves as fuel to make up the energy deficit created by not eating enough to meet all your biological requirements. As the researcher Janice Russell has said, this is akin to throwing your antique furniture on the fire to keep the house warm -- it's going to work short term, but it has long term negative implications.

Not only does this de-myelination affect brain function, but it also impacts motor function, the dependable contraction of the heart muscle, etc. etc. It can mimic the symptoms of multiple sclerosis but it is not MS (I have seen patients misdiagnosed with MS who are on the restrictive eating disorder spectrum).

De-myelinated nerves due to restriction will be re-myelinated with adequate re-feeding and dietary fats play a critical role in that process. 

Under age 25 there is additional first-time myelination that needs to happen in the frontal lobes of the brain. If you starved between the ages of 16-25 then the natural myelination process in that area of the brain did not happen. And yes it happens at whatever time you are finally able to recover fully.

Dietary fats (saturated and unsaturated) are critical for helping your body to re-myelinate all the nerves.

Beyond recovery, dietary fats are critical for maintaining nerve health and supporting reproductive cycles (particularly in women).