My screen name reflects the reason I have had to reevaluate my diet several times over my adult life, when my energy level would go from low-normal to non-existent. First time was in my late 20s...realized that my diet of eating mostly cereal, bread, peanut butter, yogurt, and fruit was leaving out protein...duh. Added it back in, which worked okay for awhile.
A few months later...after eating a big bowl of fruit with breakfast, by 10 am I would end up sitting on the couch staring into space like a zombie. Not sleepy, unable to even read...just sitting. A frutose/glucose crash, presumably. I was very ignorant about nutrition...this was in pre-Internet times but I did manage to figure out to stop eating giant bowls of fruit.
Muddled along until my mid-forties, feeling okay (for me, still low-normal energy.) Though I was eating the same CW way, my weight insidiously began increasing until reaching a max of 185. It was obvious I would soon be joining the 200 club, which was an unbearable thought. Came across the 5 Rules of Leptin concept, started following them and over about 6 months gradually lost 22 pounds. One rule was to eat 3 meals a day...I had been eating 5. It was no problem to drop the evening snack, took awhile to drop the 3 pm snack. It was easy to keep weight off without making other major changes. For awhile.
Throughout my adult life, no abnormal results have ever turned up on any medical tests, such as blood sugar, etc. Last spring, my energy degraded again until I was unable to concentrate and complete my work (I'm self-employed.) It caused me to miss a major deadline which has affected my income, naturally. I don't remember how it happened but I came across the Paleo/Primal ideas on various blogs, started buying the books, and reading. The science and evolutionary angle makes total sense to me. So far I've lost a few pounds since August, but the seriously AWESOME thing is the body-reshaping. My post-menopause big waist is not inevitable as it turns out. And I'm just about to finish up the big project from last spring.
My goal as soon as said project is outta here is to take some time off, gradually exercise more, and keep trying wacky new foods. (Roasted beef marrow today!) I suspect a familial pre-diabetes and thyroid problem combined/caused by eating too many f***ing carbs instead of real foods is behind all this nonsense.