There's a scientific answer to carb's versus fats and you can determine if you naturally burn carbs easier or burn fat easier through RER testing and determining your V0
2 max. Of course most of us won't do this test, however, it is interesting. In my family, we are all unique in what we burn. I'm a carb-burner, but I do consume a balanced amount of carbs for any activity to maintain my weight.
I do agree with the above comments that portion size means a lot and if you eat a lot of pears, then you are driving insulin even though pears are on the healthy list. As we have all commented many times, a balanced diet is a big factor too.
As for fries, I avoid ALL fried food as the oils are not healthy, however, there are a few healthy oils such as olive oil that I'm good with.
I will carb-up a bit before a work out too, but then I've been doing that all of my life, so it's kind of a habit.
Insulin is always the strongest driver in maintaining weight, and/or weight loss. Of course, the thyroid plays a role and so does your ghrelin hormone.