In terms of pure body composition, the carb source doesn’t really matter. It’s important to know this so that you don’t associate desserts, soda, or any other carbs you enjoy with guilt and immediate fat gain. For optimal health, you should be getting most of your carbs from whole foods. However, the occasional treat, assuming it fits into your daily calorie allotment, isn’t going to derail your progress. It’s much better to allow yourself to enjoy these treats in moderation if it helps you stay on track, rather than attempt to eliminate them completely and end up caving in and eating a whole cake on the weekend.