Fasting has been a godsend for me. Not only is it great for losing weight if you can handle it (it gets much easier with time), but I feel noticeably sharper and more productive when I fast.

It's fascinating how ingrained the concept of constant eating is in Western civilization. You can lose 100 pounds and keep it off, but tell people you fast and it's "but what about starvation mode? You need to eat 6 times a day or you'll die." Tell others you skip breakfast and some people actually get offended.