My cat got killed by a speeding car a few weeks ago. There is a ton of expensive, ScienceDiet weight-loss formula cat food left over. I was thinking about feeding it to the strays outside.
I'd love for them to eat and feel full but will it cause them to become even skinner? Or attack their fat cells? does anyone have information about this?

It's probably a lot better than what they're eating now! I'm sure they'll eat it, and it won't do them any harm. If you're worried about it, mix it with a regular food.
That's kind of you to want to feed the strays, it's a nice tribute to your departed cat.

I completely agree with JC. But if it still worries you, you can also donate the food to a shelter or your local animal hospital to pass on to a needy family.
I am sorry for your loss.
Prayers be with you.

It's fine. It won't do anything to harm them... but it is full of empty calories and little to no carnivorous nutritional value. Just remember that once you start feeding a stray, by law, they become yours in most all states.

It certainly wont make them lose weight. I'm sure it's more than they're getting now. Same with humans, just because you eat salads and low calorie foods, you still don't wither away into nothing. I'm sure they'll enjoy it. I'm so sorry to hear about losing your kitty.