What Suzanne said.
Even reduced fat/fat free muffins, etc are generally LOADED with sugar. I don't believe a fat free croissant exists (otherwise it wouldn't be a croissant!).
Besides the calories, another problem with starting off your day with a giant hit of sugar is that generally, eating sugar (especially in the morning) makes you crave more and more sugar throughout the day. Also, the 'burst' of energy that your body initially gets as the 'sugar rush' goes away rather quickly - meanwhile your hunger is not satisfied...which puts you at risk of eating too many calories.
Here's a tip: The more sugar you cut out of your diet, the better chance you have of taking the weight off and KEEPING it off.
In the 1990's 'fat free' was the rage but ya know what...it's SUGAR, not fat, that's generally the bad guy when it comes to obesity.
Surely your meal plan offers healthier, BETTER choices than sugary, unhealthy pastries? What about oatmeal? hardboiled egg? fresh fruit? a small handful of nuts?