Basically, you CAN do the same thing as NS, while not using the NS food. If you want to go with low glycemic food choices, simply choose cereals that are low sugar and whole grain (like Cheerios, Bran Flakes, etc.) and oatmeal packets.
For lunch and dinner-the entrees with a salad or a serving of veggies is just about right.
For snacks-you don't have to stick so much with WW desserts-you can count out a serving of pretzels, Baked Lays, a Snackwell's cookie, or any low fat/reduced calorie treat that is between 80-130 calories.
The day would be something like this:
Cereal and skim milk OR
oatmeal packet and fat free yogurt
1 piece of fruit
skim milk or fat free yogurt
entree and a salad with low cal dressing
entree and a salad or a side of veggies
Treat of 80-130 calories
This is approximately their 1200 calorie a day plan.
Nutrisystem actually was not even low glycemic, until about a year and a half ago...it was basically the same plan that it is now, or what similar to what I am describing-before they changed their cereals to whoel grain, buns/rolls from white to whole wheat, and so forth. Eating whole grains/better carbs is better for you than white/refined ones-but the basic reason that you lose on NS is because it is LOW CALORIE.