If you follow the sources to the original study, you can find out from that what the mouse chow formulation was. However, I've discussed other studies with people who study nutrition in animals (not these directly) and one problem they have run into in interpreting studies is finding out what the exact diet was. Most report the brand and formulation used, but because these are proprietary information, the manufacturers make it really hard to get details of the sources of the nutrients. All you can find out are things like crude fiber, protein, fats, calories, and certain other nutrients, but not what the source of those nutrients is (i.e., are they using corn or soy). Serious nutritionists will have custom diet formulations made rather than buying commercially available rodent chow in order to specify all of the exact ingredients, precisely for the reason you're asking, and can provide those details upon request. If that wasn't the primary question of the study though, the researchers may not have taken it into consideration. A few manufacturers do realize the need to provide these details for research diets, so do make that available upon request.
I think I understand what your question is a little better, though. You're wondering if it's not specifically the caloric restriction, but the insulin spikes after re-feeding that are having the benefits, and that seems to be a fair question. Again, I'd suggest trying to locate the original articles. It's hard to measure hormones very often in mice since they have so little blood volume, but it's possible that the study did monitor insulin or blood glucose levels, or other related measures. I think, rather than spinning your wheels looking to find out details on the diet, it would be more useful to look directly for the insulin levels over time in the animals on those diets.
Also, because I know these types of studies have been misused/ intentionally misinterpreted by some groups to support potentially unsafe diets for people, keep in mind that mice have a very different metabolism from humans, and a much shorter lifespan. Also, rodents in a laboratory tend to get fat on normal diets, so caloric restriction often doesn't mean they are underfed, just that they aren't allowed to get fat eating as much as they want to eat, so that's another reason to carefully read the details of the original study to find out what exactly that group is defining as "caloric restriction." It's not a definition fixed in stone. The same for intermittent fasting...how long, and how accessible was food upon re-feeding? Intermittent fasting could mean anything from "meal fed"...in other words, given 2 or 3 meals a day and no access to food in between meals...to food-deprived to the point of weight loss.
Food deprivation for even a day in mice has a LOT of other effects aside from just making them hungry or affecting insulin levels. Their metabolic rate is so high that they'll lose a significant amount of weight after just a short fast. Aside from all the changes in the orexigenic and anorexigenic hormones and neurotransmitters, the stress axis is activated, and reproduction suppressed.
There is an important point to be made from your question, though, and that is that such studies on caloric restriction/fasting are rather blunt tools for looking at what is extending the lifespan of those mice under those conditions. Such conditions effect a large number of changes in multiple systems in the animal, and anyone or combination of those could be what is benefiting lifespan. It also does not address whether it is affecting anything other than lifespan. There could be non-lethal conditions that are exacerbated by such a diet, or that are not easily measured in mice, or not measured in these studies. The type of question you are asking is the type of question others should ask too, and probably are, in terms of finding out just what specific thing has changed during these conditions to increase lifespan (and what is the quality of that increased lifespan).
