According to the scale, I gained 4.2 pounds in 2 days and I was sticking to my diet's calorie goal. But one meal had more sodium than I usually have in 2 days. It turned me into a sponge. To actually gain 4 pounds of fat would require 14,000 extra calories; I had 3200 total over the two days in question and burned over 3600, so it is likely I actually lost a few ounces of fat. Eat normally again for a couple of days and check it again.