I wonder how much these fasting diets are an improvement for people who are lean and already follow a "clean" diet. Is that who they are being tested on?
Just read the 5 day fasting thing. It sounds like another fancy way to get people to pay attention to yet another diet strategy to me. I didn't read anything new or controversial about it. Restrict calories and you'll be healthier! It's couched as fasting itself is the reason, which maybe is better than straight maintenance eating, I don't know.
In the article, the guy says that people at 18 or less BMI or people taking insulin (read: sugar regulation issues) shouldn't do the lowered diet. It goes without saying that the harsher in a short time frame actual fast is definitely a no-no. Basically, these crash diet deals work if you have a bunch of fat to burn off, such as being overweight/obese. If you are lean already and you aren't eating shitloads of carbs to turn into fast acting sugars with ease, fasting accelerates the rate at which you reach cellular damage. Not to mention, since you are already low on carbs in the diet already, you will go to your non-existent fat stores a lot faster, and muscle mass will decline shortly thereafter.
And as far as I've read, there are almost no examples of non-obese/cancer patients people being involved in the tests from USC that have already been published. If you follow the rabbit hole a little on the head guy, one of the most recent interviews from like June says that they are in the middle of a 70 person blind random clinical test with short term fasting and trying to prove his insulin suppresant stuff isn't just in fat rats and cancer patients. For the reasons I mentioned above (the "risks" of fasting in general), multi-day super low calorie deals will put you into muscle-consumption mode much faster than a normal metered diet would, and would mostly offer risks as you aren't getting improved bloodflow to the brain such as the fatties would to give you the feeling of having a clear head.
Honestly, the 5 day fasting-lite diet is really just your average crash short term diet, with a bit tighter control on what you eat during those 5 days than some diets. It isn't even actually fasting; it's caloric restriction rebranded. Actual fasting means you aren't taking in calories at all; no eating or drinking fortified beverages. Which is why multi-day fasting is terrible in the real world, but these "skip breakfast" type fasting gimmicks, such as the diet, are literally just calorie restiction (you know, consuming less than you use in calories) with stuff to attract the yoga-hippy set.
Which, in hindsight, is what the USC testing is really working with. Many "IF" related results are attributed to fasting but are actually just timed caloric restriction over 24 hours, not a full 24 hour no-calorie block. Really looking like misleading hippy bullshit science again. =|