Why do we keep doing something that doesn't work? Because we think our "will" can override our body's natural, primal survival instinct that kicks in whenever it perceives famine (and this happens when we suddenly cut our caloric intake, and/or when we feel deprived of what we really want to eat).
Never has this instinct presented itself more obviously to me than last week when I was on a 7-day cruise. The food was sumptuous and plentiful, and my initial response was to dive right in. I sampled three desserts the first evening.
After two days of being offered food constantly, however, I started getting turned off. By day three, nothing looked appetizing to me. Because it was a "feast" situation, and there was no chance whatsoever of famine, my body and mind naturally became discriminating. I started craving fruits and vegetables, fish, etc., because that's what my body actually desires in order to thrive.
Then something interesting (if annoyingly predictable) happened. On the final morning of the cruise, I suddenly became "hungry" again. I piled my plate with french toast, bacon, eggs, and fruit. And I grabbed a muffin to stick in my purse for later. This was the last meal, after all! I knew the feast was about to come to a screeching halt, so deprivation fears kicked in, if only for the rest of the day.
So this is how it goes. When we perceive deprivation, survival instincts take hold. When we perceive abundance, eventually we calm down.
But what we don't always understand is that humans throughout history have lived in cycles of feast or famine. We may live in a time and place where more food is always around the next corner, but our body genetics don't know that. Our cellular memory gets very nervous when we suddenly cut back on food. Our minds may be clear that we want to be slimmer, but our bodies have more serious concerns to consider.
If you're tired of struggling with your weight, I'd recommend the writings of Geneen Roth or one of the other great authors writing on this subject.
Good luck, and have a beautiful week.