How Do You Know You Are On CR: You don't, but here are some indicators
August 3, 2006
There is no measure that tells you if you are on a CR diet. This page discusses some of the indicators that you might be on CR, along with some of the issues. In spite of the issues, I think my adoption of a "CR" diet was the best eating decision I ever made.
A possible rule of thumb I have noticed is that people cut their calories significantly, reach a certain weight they are comfortable with, then hold calories at the level necessary for that weight. It seems typical for men to eat 1600 to under 2000 calories, while women end up at 1100 to 1600. But of course this varies a lot.
To avoid reading all the following, here is a summary of indicators and issues:
Calorie intake/energy expenditure - There is no definition of what number of calories correspond to CR in a human, but there are several attempts to compute this. Try Calorie Restriction Calculator
Nutrition - No one knows what the nutrition needs of humans are. The nutrition values of the food you eat, supplements you take, may be very different from the standard values. www.nutritiondata.com is a good website to get nutrition data.
Biomarkers - Few experiments (and they had few people) have been done to establish human biomarker values. CR and non-CR people can have the same biomarker values. Here is a nice biomarker chart from Dr. Luigi Fontana (best seen with Internet Explorer). And here I compare my personal results to biomarkers from studies.
Calorie Intake/Energy Expenditure
This may be the most surprising aspect of Calorie Restriction (CR): nobody knows what CR means for a human. There is no standard number of calories that defines what it means to be on CR. Animals get CR benefits if the CR group in a controlled experiment gets less calories (e.g., 30% less) than the matched control group. CR benefits increase for animals as the % cut is increased, up to a point.
But there is no control group for an individual person.
To get around this, estimates of CR calorie intake are based on "set point", energy formulas, starting weight, weight maintenance.
Why You Don't Know If You Are Eating At A CR Calorie Level
Energy Formulas - Calorie needs can be estimated based on a person's weight, height, activity level, age, and sex. The issue is there is no agreed upon standard formula. A nice example that provides you with an estimate of your CR calorie level is Calorie Restriction Calculator
Set points - The concept of a set point is that there is some weight towards which your body will naturally gravitate. This might be whatever weight you stayed at for a long time once you became an adult. Or the lean weight of your late teens, early twenties. The number of calories you require to maintain that weight would then be your starting point. You would cut calories below that amount. An issue is that there is no standard definition of a set point.
Starting weight - Take whatever weight and calorie intake you had just before you started CR and drop your calories from that point. Again, the issue is that no one knows what relationship calories to maintain current weight has to CR.
Weight maintenance - Weight loss inevitably follows substantial calorie cuts if energy expenditure does not change. Everyone who sticks with such a diet, eventually decides there is a weight below which they do not want to drop. This might be because they want to keep BMI above a minimum or simply because of looks. This establishes the number of calories eaten each day, but it is not clear if that number of calories would be a CR diet. Each person hopes it is.
In order to be on a CR diet, you must get 100% of your nutritional needs. There are two primary ways to get nutrition: from food and from supplements (you can get Vitamin D from exposing yourself to sunlight).
The best way to do this is to track what you eat very carefully, use the Agricultural Data Base to get the nutrient values, and make sure each day for every nutrient you ingest 100% of the RDA (now called the Dietary Reference Index, or DRI). One good website to get these data is www.nutritiondata.com.
If you eat a varied diet, this can be quite a bit of work. Software, even if just an Excel spreadsheet, is probably needed. One approach to lessen the work is to come up with a set of recipes that gives you all your nutrition, then eat the same food every day. Some people use this approach. Another approach is to take supplements to try to ensure you are getting your nutrition, even if the food is inadequate to do so.
Why You Don't Know If You Are Meeting Your Nutritional Needs
There are different standards for nutrition needs, for instance European standards differ from US standards. Also, the standards change over time as more is learned. In addition, nutrition requirements can be different for different individuals. The fact is, we don't really know all our nutritional needs or if the ones we do have are correct.
The food you eat does not have the same nutrients as what the tables say. Food nutrients for a given food change under different conditions - soil, time of year grown, weather, condition at harvest, how and for how long the food is stored before being eaten, how it is prepared, what the animal was fed, what drugs it was given, in what environment it was raised. So we don't really know what nutrients we ingested, we are just making our best estimate.
Different manufacturers use different industrial processes and different feed stocks with different quality controls to produce their supplements. A synthetic nutrient may not be the equivalent of the nutrient as found in food. The digestability of supplements varies, so the amount your body uses may be different from the amount on the label.
In spite of the work involved and the lack of certainty, people who begin tracking their nutrients quickly improve their diets. I believe there is a huge payoff just from this. Here is a sample of nutrient tracking from my own efforts. The first shows weekly summaries for the first half of 2006. The second shows detailed food tracking for one week.
Biomarkers are simply physiological measurements such as weight, white blood cell count, etc. There have been some controlled experiments that compare these biomarkers for people on CR against controls not on a CR diet. If a person's biomarkers were like those on CR in these experiments and not like the control group, this would be an indication a CR diet is being followed and having an effect. Also, if a person's biomarker values had changed during CR in the direction of those in these controlled experiments, that would be another indication
The web page CR Biomarkers provides a list of biomarkers and values that have shown significant differences in various experiments. The journal references for these results are also provided.
Also, Dr. Luigi Fontana, one of the leading researchers in CR, has posted a set of biomarkers that show what changes occured over a 6 year span.
I have recently (Aug, 2006) received back a set of results for my own biomarkers. I compare them to the biomarkers from studies in this table.
Issues with biomarkers
There have been very few controlled experiments using humans, so CR values of biomarkers are not well established.
Any given value of a biomarker might be found for a person on CR and for one not on CR. So far, no unique value or set of values defining a CR person has been found
Because of different procedures, instruments, and techniques, values your lab gives you may not correspond to the values provided in studies.