For me, Its a big NO! If you must eat protein bars either make or you can get some of these granola bars that are 90 calorie instead of 200. No way !!!
I only have them if I've planned ahead to have them. I found one that I really like that has 2g of sugar, 32g of protein, and 320 calories. While I'd much rather have a piece of chicken (like Scotty) there are times when I cannot. If you do eat a protein bar I highly recommend drinking AT LEAST 8 oz of water with it to help with digestion.
The calories shouldn't be a problem. Remember that you burn calories just by being awake. I recommend going to a site like http://iifym.com/iifym-calculator/ to figure out approximately how many calories you burn on an average day. That will help you figure out how many calories to eliminate to safely lose weight. Remember that calories are not the enemy, they're how we get our energy. Eating too many is the problem. And if you don't use a site or an app to help you track your calories I recommend trying one out. I use MyFitnessPal and so far it has worked well for me.
One thing I never do is substitute a protein bar (or a protein powder) for a meal. The most ideal source of all of your nutrients should be as natural as possible. Take the time to prepare a meal plan, then prepare your meals in advance. It's a lot of front-loaded work but it is SO WORTH IT.
If I wanna grant myself an extra protein boost, especially after a tough weightlifting session, I go with sardines: almost 25% of protein (exceeds beef or eggs, only chicken breast is close), only 5% fat, almost Zero carbs, low calories and a lot of healthy omega-3 fatty acids.
Hey there. Interesting question and it's normal to get so many different opinions. I added them to my, after workout routine, for over a year now and I can say that they have a positive effect so far. You should check out this article about protein bars and see for yourself.
My personal favorite is the Chocolate Coconut but I love all of their products because they are gluten free!