I am often asked with great anticipation to describe the “calorie restriction diet”. Questioners presume that there must be an intricate program with elaborate rules regarding what to eat and when to eat it. I know this because I have had this conversation many times and people are always disappointed with my first reply and therefore will take several runs at the question before abandoning the effort, concluding finally that I am either evasive or obtuse.
My theory is that diets are more credible (and attractive) if they  consist of specific rules and procedures (especially when clothed with a glib scientific idea). The more popular diets come packaged in attractive books and include a generous array of recipes. Better still, some diets are sold as turn-key programs: They provide the meals themselves along with a wide array of supplements. But best-selling diets need more than elaborate programs and attractive packages. They need an “expert” that is winsome, articulate and telegenic (or, failing these, a celebrity). Programs built around points, portions and protein have proven hugely popular. 
Unfortunately, calorie restriction lacks virtually all the elements essential for commercial success or, for that matter, even basic credibility. There are no celebrity promoters, no products to provide. There is not even a detailed program to present to prospects. The only books on the subject tend to lack the packaging and the promoters that produce best-sellers: The diction is not as user-friendly; the fact-filled content dwells heavily on scientific research and technical explanations; the recommendations lack the terse certitude consumers crave; and the authors do little for themselves or their books in the few interviews that come their way.

The unsatisfying fact is that CR practitioners are unanimous on only two things: 1) we must reduce our calorie consumption substantially below our respective set points, 2) we must maximize the nutritional content of the calories we consume. Beyond these fundamentals, strategies and tactics vary. While prong 2 does assure that all practitioners eat generous quantities of fruits and vegetables, strategies vary regarding carbs vs. fats vs. protein percentages in each diet. Practices also vary among us regarding the related issues of bread and dessert permissibility. Positions also vary regarding meat & dairy consumption, though it’s fair to say that most of us minimize or eliminate these. Some of us, but not all, take lots of supplements, consume alcohol and/or caffeine, prefer raw foods, eat only organic, etc.. 

Regarding exercise, prong 1 creates a general consensus that the calorie restriction effect can be nullified by too much exercise. CR is not about being lean, its about restricting calories. That being said, the actual amount of exercise varies greatly among practitioners. Some push the envelope in my humble opinion. People have told me they were doing CR while regularly exercising an hour a day. The problem is that there is no clear guidance on this point. We know that exercise is good since it benefits us in so many ways, not the least of which relates to our functional health (bones, muscles, flexibility, etc.). The key question is how many exercise calories can we expend without the caloric detriment outweighing the caloric benefit. We know, for example, that heavy aerobics activity--which by definition requires heavy calorie consumption-- does not produce exceptional longevity (though it improves average longevity).

Our strategies also vary regarding how we schedule our meals. Some of us eat 3 meals of approximately the same size each day. Some eat only one or two meals; others eat more but eat larger meals early in the day. Some snack. Others eat only on alternate days. The research does not indicate that any of these is clearly the best approach. I suspect each of us chose the pattern that we can live with best, then developed our supporting arguments.

Despite, however, the marketing challenges facing calorie restriction, there still remains the preponderating fact that CR is the most intelligent diet option available to man at this time. No eating strategy has been shown to provide better protection against all major diseases, to preserve physical functionality longer and to provide, potentially at least, dramatically greater longevity. Furthermore, not only are these claims greater than those of 95% of the more popular diets, the documentation supporting these claims dwarfs that of its best-selling counterparts (for which in many cases no such evidence exists). Therefore, my path is clear. Along the way I will continue being one of those voices in the wilderness for which an occasional convert is ample satisfaction.