Like most futurist-oriented people, I am fascinated by the idea of long-term life extension -- the notion that eventually people will have life expectancies of hundreds of years; thousands of years; or even more.  Although medicine has a ways to go in this area, one obvious approach is to take low tech steps to increase one's lifespan in hopes of living long enough to take advantage of possible future advances.  i.e., to roll with +1 dice.  Besides the obvious steps like wearing seat belts; getting regular exercise; eating a lot of fruits and vegetables, calorie restriction presents itself as an intriguing possible method of life extension.

In this essay, I will attempt to briefly define calorie restriction; assess how useful it might be; speculate about how it might be useful; and use the foregoing to justify my own personal approach to calorie restriction, which I will describe presently.  Of course I welcome comments and criticisms, especially since I am messing around with my own health.

I should note at the outset that I have no formal training or credentials in medicine nutrition or anything like that.  I'm just an attorney.

I should also add that my approach to calorie restriction is not a diet in the sense of being a weight loss strategy for people who cannot control their eating.  This is not a weight loss post!  I do not describe in this essay how I control my eating; control is assumed.

Last, my general approach is one of no regret.  i.e. My main priority in calorie-restricting myself is to avoid doing anything too radical in terms of loss of quality of life or risk to my health.

I. What is Calorie Restriction?

Wikipedia defines "calorie restriction" as follows:

Caloric restriction (CR), or calorie restriction, is a dietary regiment that is based on low calorie intake. "Low" can be defined relative to the subject's previous intake before intentionally restricting calories, or relative to an average person of similar body type.

So immediately we see a problem -- the concept of calorie restriction is ambiguous.  How am I supposed to evaluate and possibly implement calorie restriction in my life if I am not even clear on what it means?  This is not just a problem for laymen like me.  Imagine you are a researcher who is studying the effects of calorie restrictions in lab chimps.  How do you feed your control group of lab chimps?  Do you let them eat donuts and potato chips ad libitum?  Do you limit them to chimp chow?  Without a clear definition, this is a bit of a conundrum.

In fact, one individual has argued that the difference in treatment of control animals may be part of the reason why two studies on calorie restriction in monkeys had different results:

Further, the NIA study control monkeys were not truly fed ad libitum, unlike the WNPRC study. The regulated portioning of food for the NIA control monkeys may be a slight restriction and, thus, largely prevented obesity. Studies of 10% CR have been reported to increase lifespan in rats compared to ad libitum controls – even more than 25% and 40% CR²⁰. The NIA control monkeys may experience survival benefits from this slight restriction.

http://www.crsociety.org/science/nia_monkey_study

Another individual states as follows:

"Both the NIA and U Wisc studies need to be considered together for proper interpretation. It is clear that the U Wisc "controls" differ from the U Wisc CR group and BOTH NIA groups, and are probably most like the general populations of developed countries.

Because we at NIA wanted to avoid the criticism leveled at many rodent CR studies that controls are overweight and sedentary, we specifically designed our dietary conditions to supply an adequate, but not OVERadequate, caloric intake.

The bottom line is that, for most people (who are more like the U Wisc controls), CR may indeed provide both health (BOTH studies agree on THIS) and longevity benefits.....and of course, most important.....more "healthy years."

https://www.crsociety.org/index.php?/topic/2939-dr-george-roth-comments-on-calorie-restriction-and-nia-monkey-study/

For purposes of this essay, I will offer the following definitions:

1.  "Mild calorie restriction" = restricting calories sufficiently so that you avoid gaining large amounts of weight.

2.  "Moderate calorie restriction" = restricting calories sufficiently so that most of the time you are towards the bottom of your metabolic range.

3.  "Severe calorie restriction" = restricting calories sufficiently so that you end up spending your time significantly below typically fit people in terms of muscle mass and/or body fat.

The first and third definitions are pretty straightforward, although it's worth noting that a lot of people engage in mild calorie restriction unintentionally, just through the operation of their natural system which regulates their appetite/urge to eat/urge to stop eating (John Walker calls this the "food clock.")

The second definition requires a little explanation.   From simple observation, it appears that small changes in one's energy intake result in corresponding changes in one's metabolic rate.  So that if your weight is stable but you eat a little more or less than usual, you might notice that you are a little warmer or cooler than usual.  Evidently the body can and does make small adjustments to its metabolic rate in response to changes in food intake.  This is also consistent with dieters' reports that they feel cold when dieting.

II.     Does Calorie Restriction Work in Humans?

It seems quite likely that mild calorie restriction works in humans based on the observation that fat people have significantly greater mortality than thin people.

For example, as illustrated by the charts here:

http://www.nejm.org/action/showImage?doi=10.1056%2FNEJMoa1000367&iid=f01&

Of course one cannot know this for sure since there is no ethical way to do a large controlled experiment, but still it's reasonable to infer cause and effect:  Common sense says that being fat puts a lot of abnormal extra strain on your system almost all the time.  In any event, there seems to be little downside to mild calorie restriction.

A more interesting question is whether moderate calorie restriction works in humans.  Common sense says that it ought to be beneficial based on the idea that slowing one's metabolism ought to slow the aging process, all things being equal.  One interesting area of research is studies which look at the effect of modest weight loss among obese people.  Is someone who goes from 250 pounds to 225 pounds and stays there more healthy than someone who goes from 210 pounds to 220 pounds and continues to gain weight?  If so, part of the difference might be that the second person is towards the top of his metabolic range while the first person is towards the middle or bottom.

The Calorie Restriction Society web site links to a couple presentations which argue that cancer is actually a metabolic disease related to having too much energy in play.  I'm a bit skeptical of this claim, but it does seem to me that you are inviting trouble by having extra energy floating around in your system.

As for severe calorie restriction, the jury is still out.  I don't put too much stock in the left side of the J-shaped curves comparing body weight to mortality.  Surely a lot of underweight people have serious latent health problems.  What's more interesting to me is that the curves flatten out between BMI of about 19 and 23.5.  This suggests to me that one can realize most of the benefits of reduced body mass by being normal weight and that after that, if there are any benefits, it's diminishing returns.

III.   My Approach to Calorie Restriction

I have decided to adopt an intermediate approach to calorie restriction, i.e. the aim is to stay thin and be towards the bottom of my metabolic range most of the time.  The health benefits to staying thin are pretty clear; there doesn't seem to be much downside; and frankly there are a lot of social benefits.  The benefits of staying towards the bottom of my metabolic range are more iffy, but again there doesn't seem to be much downside to it.  (Putting aside issues of health, the main downside is that it happens pretty frequently that I will have a meal and eat less food than I would have liked to eat.)

Severe calorie restriction seems too speculative to me to be worth the trouble.  Particularly given the social costs and the likely diminishing returns problem.  I like having a somewhat muscular appearance as opposed to a gaunt appearance.  Since my main priority is to avoid regrets, I am not willing to go this route without pretty solid evidence of benefit.

IIIa.  The Nuts and Bolts

What I do is this:  I have a basic daily diet which I believe is reasonably healthy and well-balanced.  Although it is somewhat flexible, it contains roughly the same proportions of macro-nutrients and is roughly the same amount of calories each day.  From careful observation, I have determined that my basic daily diet is about 500 to 600 calories short of my actual daily caloric needs.  i.e. if I stuck to my basic daily diet and ate nothing more, I would lose about a pound a week.  I add a small supplement of extra food to my basic daily diet if I work out at the gym in order to balance out the exercise.  (Interestingly, I once measured and it seems my basic daily diet, including the exercise supplement, is about 2800 calories.  This seems pretty high for a man who is thin, slightly below average height, and only slightly muscular in build.  I'm not sure what to make of it.)

I weigh myself every morning and calculate a 7-day moving average of my weight.  I then subtract this number from a pre-determined reference weight and multiply the result by 100.  This is the number of additional calories I consume that day in the form of reasonably healthy foods.  The idea is to eat close to the minimum to maintain weight, thus staying thin and towards the bottom of my metabolic range.

Now and then my weight spikes upward when I have an event which involves a lot of eating; after that it drifts back down again.  I've been calorie-restricted in this way for some time now.  I feel perfectly fine but after every meal I feel like I could easily eat more.  I pretty much never get heartburn anymore.  I usually wake up quite hungry.  These are about the only effects I have noticed.

IV.  Self-Criticisms of My Approach

In the interest of rationality, it probably makes sense to offer some self-criticism:

1. I found the above scientific references only after I had settled on my approach to calorie restriction.   So there is probably a certain backwardness about my reasoning.  My conclusion is based more on my own intuition, reasoning, observations and common sense than on scientific research.

2.  It never occurred to me to regularly measure my body temperature before and after starting this program.  Which is unfortunate because it may have given me some useful information about the effects of my diet on my metabolism.

3.  There's really no way to measure if any of this is having an effect on my rate of aging.  Without this sort of feedback, I'm pretty much shooting in the dark.

V.  Conclusion

So that's about the extent of my self-experiment.  It's a bit frightening that I'm putting my own health on the line in the face of so much uncertainty.  At same time, it seems like a reasonable, conservative approach which is unlikely to lead to regrets.  Of course there is an excellent chance I will never know how much of an impact my lifestyle had on my overall health.

Anyway, I welcome any intelligent thoughts, suggestions, constructive criticism, etc.