I am 29 and have noticed this happening to me. I have been yo yo dieting for 10 years (eeek!!) and thought it was easier to lose until the past 2-3 years. It was always hard work but it just seemed to come off faster. I am not sure if I just was more motivated and was more consistent. Maybe now I get frustrated if I don't see instant results which I obviously know is not the way to go. I need to be consistent but my patience is wearing thin, esp because I have been doing this for so long.
Hang in there! we will do this!
