Snack packs may not be the healthiest food choice out there, but if they will keep you satisfied and help you to reach your weight loss goals than go for it. It's not what you do some of the time that matters, it's what you do all those other times. Don't stress it.
Otherwise try to avoid processed foods that contain any of these in the first four ingredients; enriched flour, high fructose corn syrup, hydrogenated oil, trans-fats, sugar, or white flour.
The problem with corn syrup is that it doesn't stop you form feeling hungry so you end up eating more calories. When your stomach is empty it secretes the hormone ghrelin which signals your brain to eat something. After you eat something such as an apple, the ghrelin stops being sent. Corn syrup doesn't stop ghrelin from making you hungry as it should, but it also prevents another hormone called leptin from telling your brain when you're full.
Interstingly people that diet have higher amounts of ghrelin than other people, making it even harder to stay on a diet.
Eight Ways To Improve Nutrition
http://www.realage.com/doctorCenter/...aspx?aid=10441
'You On a Diet' The 99 Second Edition
http://www.realage.com/doctorCenter/...aspx?aid=10447