Calorie Restriction

This morning I stumbled across an article in the New York Times on an interesting clinical trial financed by the National Institute of Health of the implications of a calorie-restricted diet on aging. In the study they pay the subjects substantial stipends (although when worked out by the hour it isn’t much) to restrict the calories they consume rather drastically and undergo a series of tests on an ongoing basis.

There were two aspects of the study that I found particularly intriguing. The first was the initial evaluation process:

At the start of the Calerie experiment, a first order of business was to rigorously determine how many calories each recruit ate and burned on a typical day. This required a methodical (and expensive) two-week laboratory test: participants drank water containing rare isotopes that, when excreted and analyzed, allowed researchers to discern a subject’s carbon-dioxide production (and his or her calorie burn) to a precise degree. After that, each subject received an individualized target. Most of the subjects I spoke with called this the Number. At the start, researchers determined that Doug Hansen burns (and thus ingests) what he told me was around 2,600 calories a day. So he was put on a diet of 1,950 calories. Jeffrey Peipert, an Ob-Gyn who is nine months into the study in St. Louis, was found to burn 3,300 a day — and thus given a number of just under 2,500.

In other words, they’re restricting the calories they consume per day to 25% below the number of calories they burn per day. Couple that with this:

At the start, the recruits taking part in what is called calorie restriction were told they would likely see their weight decrease by around 15 percent during the first year. (A smaller number of recruits were put in a control group and instructed to continue their normal eating habits for two years.) After their weight drop, they would plateau at a “weight stability” level. This was Hansen’s experience, as well as that of most of the Calerie subjects I met. After six months in the study, Hansen told me, he dropped to 168 pounds from 198, or near his plateau.

The emphasis is mine.

Now, if you believe that weight loss can be achieved according to the simple equation

Weight loss (in calories) = Calories consumed – Calories burned

that cannot be. Unless they’re cheating. But these subjects are being monitored very closely specifically to prevent cheating.

This particular result would seem to substantiate the anecdotal reports of some of the people who say they simply cannot lose weight regardless of how little they eat. At least some of them may not be mistaken, lying, or cheating.

My view is that human physiology is too complicated for simple equations. The human body has too many ways of using and conserving energy for simple equations to work and, well, people are different. One size does not fit all.

Let me use myself as an example. About 12 years ago I made a major change in my diet. I started measuring what I was eating very carefully. Since then I’ve been eating about 1,800 calories per day carefully balanced among proteins, carbohydrates, and fats. I’ve also maintained as high an activity level as I was able, mostly walking but other activities as well. I walk between three and five miles per day, 365 days a year, and have done for more than 12 years.

According to the simple formula I should be losing weight. Or gaining weight. I’m not. I’ve maintained nearly the same weight as when I started.

Now in my case there’s a complication. My measured body temperature at rising is typically 94 degrees or below and it rarely goes above 97 degrees. Of itself that reduces my nominal caloric requirements. As I said, one size does not fit all. I am euthyroid, in case you were wondering.

I do find these experiments in human behavior and physiology fascinating. I doubt that they’ll convince people to undertake spartan diets of the sort in the experiment on a longterm basis even if it does extend their lifespan (that isn’t the objective of the experiment). We just aren’t built that way.