Sometimes blood sugar fluctuates because of the foods we are eating - the pudding cups have 17 grams of sugar, which is almost the same amount as a Hershey's chocolate bar. If your sugar is fluctuating, gradual rises will help also give you a gradual drop. It's the spikes that drop more quickly and keep you in that yo-yo of fluctuations.
Even worse, since you are insulin resistant, that glucose 'spike' means that your pancreas is working overtime making oodles of insulin because it can't sweep away that glucose effectively. And all that excess insulin makes weight loss slower and weight gain easier.
A 'perfect snack' would be an apple and a cheesestick. It may give you about the same grams of sugar, but they will be of a different sort - fructose (apple) versus sucrose (table sugar in pudding), plus you get protein from the cheese stick that will also help balance your sugar. Protein takes more time to digest than sugar, so it slows down the glucose response, which is a good thing.
However, with all that said, if you can lose weight and still eat sugar, more power to ya! But if you have difficulties, you might want to try and opt for something that is gentler on your glucose response. Another diet plan with balanced carbs and protein that you might like is Body for Life. It's all about balancing protein with carbs. I liked Body for Life for Women even better. Great book, with simple recipes. I learned a lot from both of the books.
I hope this helps! It stinks to be IR, but it gets easier as we go along.