Food for thought

Ironically, the unsuccessful dieter is usually an intelligent, educated,  highly motivated career professional who excels in other areas.They are nutritionally savvy individuals, with an abundance of knowledge on weight loss. But in spite of endless choices (acupuncture, high protein, low carb, hypnosis, Weight Watchers, The Zone Diet,  Jenny Craig, South Beach,(just to name a few), they have inevitably failed at their efforts.
WHY?