I heard the ideal death described as pretty solid health up to a very rapid decline, healthy food probably helps that.
If only if it was as simple as enjoy junk food and your life and die a few years younger.
It's like when someone says I rather smoke and die at 75 vs 80. Sure, but then you spend more time at the doctor's, you get exhaust faster, you are not always fun to be around with because your clothes may smell like cigarette and more.
I'm currently on a calorie-counting streak coming up on a year, and I have managed to do it without switching to foods I don't enjoy. The guiding principle is to look at nutrition labels for calorie information, then choose foods that are low-calorie, enjoyable, and that make me feel full. (That means, generally, more high-protein items like meat and more high-fiber items like vegetables.)
I've made some effort to switch to healthier foods, but mostly I just started with the foods I like and filtered that set down to eliminate the worst ones. I still eat frozen pizzas and ice cream, but I do carefully measure the portions on those.
Anyway, if calorie restriction is the thing that actually gives you health benefits, then I feel like I'm doing that without dooming myself to a life of foods that I don't enjoy.
As someone has pointed out above, it seems like the calorie restriction is not really the reason for improved health. The real reason seems to be that reducing calories happens to also reduce all the stuff that makes us sick in the first place, like pro-inflammatory vegetable oils, sugar, and refined carbohydrates. If you look at the actual studies mentioned in the article, you'll see that the NIA study didn't find any difference between the two groups of monkeys, while the UW study did. The primary difference between the two is that the NIA fed the monkeys varied protein sources, while the UW study fed them significantly higher levels of sucrose. We already know that sugar is bad for you, so it makes sense that reducing its intake would improve health. The CR is a red herring.
I also checked some of the iDiet recipes, and I'm pretty sure they will do you more harm than good. Margarine, like pretty much any vegetable oil other than olive/avocado/coconut, is really bad for you. Egg yolks are not bad for you at all and I wouldn't worry about cholesterol in food (this is a whole topic in and of itself that I won't really go into here). One of the recipes on there is oatmeal with maple syrup; that is just sugar and grains, which honestly just feels like a slightly healthier frosted flakes.
Do you have sources for that? Which vegetables oils are healthy and which are unhealthy and why?
The only relevant knowledge I have is that saturated and trans fats are bad and that unsaturated are good. One source for that is for example https://www.hsph.harvard.edu/nutritionsource/what-should-you... .
If this is what you are refering to then margarine is indeed bad because it often contains high amounts of trans fat but for example coconut oil isnt good either for its high saturated fat content. Plenty of other vegetable oils should be fine judging by their fat contents rather than "really bad".
I know this wasn't your point but: I don't think people recommend eating margarine instead of real butter anymore.
I won't claim to know if avoiding egg yolks is healthy or not, but many seem to think that dietary cholesterol isn't as bad as once thought.
https://www.theidiet.com/food/idiet-recipes/vanilla-spice-co...
And here's their cake made with egg whites, which I imagine is great for crying yourself to sleep while trying to ignore your hunger: https://www.theidiet.com/food/idiet-recipes/idiet-chocolate-...