Not very credible. Another youtube video. Admits she lost weight on other diets as well.
Also, being a marathoner myself, she didn't lose weight by eating 3,000 cals per day. She lost weight because she exercises. You can't lose weight unless you burn more calories than you eat, simple math.
That's what you keep failing to mention. If you eat 3,500 calories more than you burn, you will GAIN one pound. It's a physiological, biological, scientifically proven fact.