As I understand it the excess calories should be transferred into storage (FAT) when the digestion process is complete. There is no middle holding area or middle ground for food consumed. The problem here is that a single pound is very difficult to see or measure.

I have been at my goal weight for 18 months but my goal weight is really say a 5 pound range. I don't weigh the same amount two morning in a row when I step on the scale almost invariably it is up or down by a pound or two. One of the biggest contributors to weight fluctuation is fluid retention. Our bodies are 80%+ water. A gallon of water water weighs eight pounds so if you manage to retain an additional 32 oz of water you will "gain" 2 pounds. Over the Christmas holiday I was taking a non-steroidal anti-inflammatory drug naproxen sodium (prescription Aleve) and over the course of 9 days I put on 14 pounds while my diet remained the same. I stopped taking the drug, lived in the bathroom for two days and was back at my normal weight.

Some folks will mention muscle gain as a reason for weight gain. We gain muscle quite slowly, cardio activity like riding or running don't tend to bulk people up (sure you do gain muscle over time but not big heavy bulky muscles). Five pounds of muscle is a lot of muscle. A person can't gain weight in muscle without eating more than they are burning either. In order to build muscle bulk a person MUST actually consume the additional calories necessary to grow that muscle.

If the numbers you quote are accurate I would attribute your change in weight to a fluid change. If that is the case it should disappear as rapidly as it arrived.

Good Luck.