Yes, a lot of times fat loss can be inhibited by hormones such as insulin.
Every time you eat insulin is released, however eating starchy carbohydrates releases the most amount of insulin.
For most people it takes almost a week to bounce back from an entire day of bad eating.
On days of training 30-60 minutes after a workout. On days off of training first thing in the morning is optimal.
20-30 minutes before a workout is optimal for a Pre-workout drink.