Maybe because it might actually be the same thing? I'm not talking about constant, long term low calorie eating here. But intermittently eating lower calorie really is different from constantly eating lower calorie. What is it about fasting that (hopefully) prevents adaptation to lower calories, slowing of the metabolism? Arguably it's likely to be the higher calorie eating in between the fasting, and not the fasting itself. People talk about fasting not lowering the metabolism--this is true in studies where the fast itself is 24 hours, at most 48. When Cahill fasted young divinity students for a week, their metabolic rate went down to 1100 calories a day. Young guys in their twenties, their basal metabolic rates should have been at least 1600 calories a day, probably a bit more--that makes the reduction in metabolic rate at least comparable to what happened in the Minnesota (semi-) Starvation study. More recently we have the Matador study--that had a protocol with a couple weeks of lower calorie, a couple weeks of regular eating--and the result was a maintenance of metabolic rate. Short term fasting might not lower metabolic rate--but neither does short term calorie restriction.

Now, of course it's still different from just fasting, and that's something I want to see studied more. But I also want to see what Longo's up to, and more stuff like the Matador study as well. Showing the ins and outs of all this stuff, and benefits of various fasting versus various lower calorie protocols is going to need a comprehensive look at all these different approaches.