How Stone Age Diet Made One Berkely Professor Skinny.

In case you don’t know there is an awesome book called Freakanomics, written by Steven Levitt and Stephen Dubner. They also publish a column in The New York Times Magazine. This happens to be my favorite one.

Does the Truth Lie Within?

By STEPHEN J. DUBNER and STEVEN D. LEVITT

Seth Roberts is a 52-year-old psychology professor at the University of California at Berkeley. If you knew Roberts 25 years ago, you might remember him as a man with problems. He had acne, and most days he woke up too early, which left him exhausted. He wasn't depressed, but he wasn't always in the best of moods. Most troubling to Roberts, he was overweight: at 5-foot-11, he weighed 200 pounds.

When you encounter Seth Roberts today, he is a clear-skinned, well-rested, entirely affable man who weighs about 160 pounds and looks 10 years younger than his age. How did this happen?

It began when Roberts was a graduate student. First he had the clever idea of turning his personal problems into research subjects. Then he decided that he would use his own body as a laboratory. Thus did Roberts embark on one of the longest bouts of scientific self-experimentation known to man -- not only poking, prodding and measuring himself more than might be wise but also rigorously recording every data point along the way.

Self-experimentation, though hardly a new idea in the sciences, remains rare. Many modern scientists dismiss it as being not nearly scientific enough: there is no obvious control group, and you can hardly run a double-blind experiment when the researcher and subject are the same person. But might the not-quite-scientific nature of self-experimentation also be a good thing? A great many laboratory-based scientific experiments, especially those in the medical field, are later revealed to have been marred by poor methodology or blatant self-interest. In the case of Roberts, his self-interest is extreme, but at least it is obvious. His methodology is so simple -- trying a million solutions until he finds one that works -- that it creates the utmost transparency.

In some ways, self-experimentation has more in common with economics than with the hard sciences. Without the ability to run randomized experiments, economists are often left to exploit whatever data they can get hold of. Let's say you're an economist trying to measure the effect of imprisonment on crime rates. What you would ideally like to do is have a few randomly chosen states suddenly release 10,000 prisoners, while another few random states lock up an extra 10,000 people. In the absence of such a perfect experiment, you are forced to rely on creative proxies -- like lawsuits that charge various states with prison overcrowding, which down the road lead to essentially random releases of large numbers of prisoners. (And yes, crime in those states does rise sharply after the prisoners are released.)

What could be a more opportunistic means of generating data than exploiting your own body? Roberts started small, with his acne, then moved on to his early waking. It took him more than 10 years of experimenting, but he found that his morning insomnia could be cured if, on the previous day, he got lots of morning light, skipped breakfast and spent at least eight hours standing.

Stranger yet was the fix he discovered for lifting his mood: at least one hour each morning of TV viewing, specifically life-size talking heads -- but never such TV at night. Once he stumbled upon this solution, Roberts, like many scientists, looked back to the Stone Age for explication. Anthropological research suggests that early humans had lots of face-to-face contact every morning but precious little after dark, a pattern that Roberts's TV viewing now mimicked.

It was also the Stone Age that informed his system of weight control. Over the years, he had tried a sushi diet, a tubular-pasta diet, a five-liters-of-water-a-day diet and various others. They all proved ineffective or too hard or too boring to sustain. He had by now come to embrace the theory that our bodies are regulated by a ''set point,'' a sort of Stone Age thermostat that sets an optimal weight for each person. This thermostat, however, works the opposite of the one in your home. When your home gets cold, the thermostat turns on the furnace. But according to Roberts's interpretation of the set-point theory, when food is scarcer, you become less hungry; and you get hungrier when there's a lot of food around.

This may sound backward, like telling your home's furnace to run only in the summer. But there is a key difference between home heat and calories: while there is no good way to store the warm air in your home for the next winter, there is a way to store today's calories for future use. It's called fat. In this regard, fat is like money: you can earn it today, put it in the bank and withdraw it later when needed.

During an era of scarcity -- an era when the next meal depended on a successful hunt, not a successful phone call to Hunan Garden -- this set-point system was vital. It allowed you to spend down your fat savings when food was scarce and make deposits when food was plentiful. Roberts was convinced that this system was accompanied by a powerful signaling mechanism: whenever you ate a food that was flavorful (which correlated with a time of abundance) and familiar (which indicated that you had eaten this food before and benefited from it), your body demanded that you bank as many of those calories as possible.

Roberts understood that these signals were learned associations -- as dependable as Pavlov's bell -- that once upon a time served humankind well. Today, however, at least in places with constant opportunities to eat, these signals can lead to a big, fat problem: rampant overeating.

So Roberts tried to game this Stone Age system. What if he could keep his thermostat low by sending fewer flavor signals? One obvious solution was a bland diet, but that didn't interest Roberts. (He is, in fact, a serious foodie.) After a great deal of experimenting, he discovered two agents capable of tricking the set-point system. A few tablespoons of unflavored oil (he used canola or extra light olive oil), swallowed a few times a day between mealtimes, gave his body some calories but didn't trip the signal to stock up on more. Several ounces of sugar water (he used granulated fructose, which has a lower glycemic index than table sugar) produced the same effect. (Sweetness does not seem to act as a ''flavor'' in the body's caloric-signaling system.)

The results were astounding. Roberts lost 40 pounds and never gained it back. He could eat pretty much whenever and whatever he wanted, but he was far less hungry than he had ever been. Friends and colleagues tried his diet, usually with similar results. His regimen seems to satisfy a set of requirements that many commercial diets do not: it was easy, built on a scientific theory and, most important, it did not leave Roberts hungry.

In the academic community, Roberts's self-experimentation has found critics but also serious admirers. Among the latter are the esteemed psychologist Robert Rosenthal, who has praised Roberts for ''approaching data in an exploratory spirit more than, or at least in addition to, a confirmatory spirit'' and for seeing data analysis ''as the opportunity to confront a surprise.'' Rosenthal went so far as to envision ''a time in the future when 'self-experimenter' became a new part-time (or full-time) profession.''

But will Seth Roberts's strange weight-control solution -- he calls it the Shangri-La Diet -- really work for the millions of people who need it? We may soon find out. With the Atkins diet company filing for bankruptcy, America is eager for its next diet craze. And a few spoonfuls of sugar may be just the kind of sacrifice that Americans can handle.