Hmm, this may help explain how I've maintained my weight even though my food journal logging says that I run about a 1000+ calorie deficit:
In one study, dietitians were asked to estimate calories in three fast-food meals. The baseline meal consisted of a three-inch ham sandwich, six chips and a 10-ounce cup of soda. The portion size was doubled in the second meal and doubled again in the third meal. Yet even the dietitians failed to see it, guessing 13 percent to 26 percent too low on the calorie counts. Of course, each of these mistakes is small on its own, but over time, our errors in portion perception can add up. For a weekly moviegoer who orders a supersize soda to sip on, the misperception translates to about 8,000 unintended calories a year.
Or it could be that I've overestimated my daily burn rate.