Fighting weight?

Thai Guy (like the hubby's new bloggy name?) is running the marathon with me next Saturday but it's purely a bucket list thing for him. His first true love is MMA (mixed martial arts. Think Ultimate Fighting Championships- boxing, wrestling, jiu-jitsu, muay thai kickboxing, you name it!)  He's been working out at a MMA gym for the past year and half.  His original goal was just to get in shape but that has slowly turned into a desire to fight in his first amateur fight.  Pretty much everyone thinks he's crazy because he's 36 and anciently old for the sport "no spring chicken" but I am excited for him! It's something he's really passionate about and I love to see him meet his goals. (Yes, I'm the perfect, loving wife.)  Anyway, how could I not be supportive?! He is running this marathon with me even though he said it was something he would never do. In fact, I think his actual words were- "I don't even like to drive 26 miles!  Why on earth would I run that far?!" That being said, I'm not really in love with the idea of watching him get punched in the face but it is kinda' manly and hot, don't ya' think?

Anyway, right after the marathon he is starting this Fighter's Diet, which is a program that was put together by one of the trainers at his gym. It's a 100-Day Challenge that starts with a 6 week cutting phase. I signed up to do it, too, but now I'm not so sure. According to the info I got today, the first 6 weeks you are limited to 7 foods:

1. Cage-free brown eggs with yolks
2. Baby organic spinach
3. Extra-virgin olive oil
4. Vegetable based salsa
5. Low fat cottage cheese
6. Canned chicken breast or canned albacore tuna
7. Roasted, grilled, or baked chicken breast

That's it. Also, I did the math and according to them, at my weight, I should be eating about 850/cal a day during that time (500 cal less than my BMR).  Is that crazy?! That's crazy, right? Thai Guy is convinced that he needs to see this challenge through to be in ultimate fighting shape by April (by his first fight.)  However, I'm not so sure that will be enough food for me to meet my running goals.  I told him that I'll do it with him for a week but then I might need to find another nutritional plan.  I don't doubt that I could lose some serious pounds this way but at what cost?

Anyway, have you ever tried a crazy diet like this?  Did it affect your running?