I blame carbs more than insulin. I think that with weight training, it's important to time carbs to fuel workouts. If you like lifting and are getting good results (i.e. stronger!) I wouldn't cut back on working out. I'd look at timing the carbs specifically to fuel your workouts. Maybe cut back in other areas and work to replace some carbs with something like veggies (which are carbs, but not as much, and tons of vitamins) or protein. I used to eat cereal, granola bar snack w/ yogurt, sandwich, chips, apple, then whatever (tons) for dinner and weighed 275 lbs. I've worked out a lot but have made the most weight gains cutting out carbs. These days I mostly eat eggs or egg beaters w/ veggies (broccoli/ spinach, maybe cheese) for breakfast, 1/2 sandwich, veggies and plain Greek yogurt for lunch and then dinner.
I am more cognizant about what I eat but when I'm working out, I work to arrange my BG so it will be where I want it to be. If it's not, I still figure out a way to work out and keep at it. If 150G of carbs is gaining 1 lb/ week, try 130 and see if it works for you.