Sky King, our golden retriever, knows that I wouldn’t perform an experiment on him that I hadn’t first tried on myself. Otherwise I doubt he’d be so eager to join in my efforts to advance the progress of gastronomical science. It was just the other day that we gave Sky King a sprig of stevia, a native plant of South America—four small green leaves on a stem. Chewing stevia leaves is a remarkable experience, especially the first few times. Initially, it tastes of nothing, sort of green and slightly bitter. Then, as you chew, your mouth is filled with the sweetest taste you’ve ever known, a pure, cool, piercing, disembodied sweetness, peaking in about 30 seconds and soon replaced by an unpleasant bitterness.

I was sure Sky King would love it. He is as fond of candy as he is of Chinese food or coconut cake, which always leaves a blob of fluffy whiteness on his big dark nose. Yet it took him no more than a few seconds to spit out the stevia. In actual fact, dogs don’t know how to spit; at least ours doesn’t. He just let the leaves fall out of his mouth. That was the end of Experiment #1. (Let me reassure you: No golden retrievers have been harmed in the preparation of this article. And before I administered the stevia to Sky King, I combed the medical literature to learn whether a little stevia can hurt animals, either canine or human. It’s been given to both kinds of animals, and there’s never been a problem.)

You can expect to find lots of stevia in your own future. Stevia is an herb first described in 1899 by a Swiss botanist working in eastern Paraguay, where it had been used for centuries as a medicine and a sweetener. In 1931, French chemists identified the sweet compounds in stevia, glycosides named stevioside and rebaudioside. In 1995, the leaf and its extracts were approved by the FDA as dietary supplements, and finally, in December 2008, the FDA granted petitions by Pepsi and Coke to sell stevia, which they promptly brought to market the next year as tabletop sweeteners PureVia and Truvia, respectively, followed by low-calorie beverages SoBe Life Water and Sprite Green. Right now stevia is the non-caloric sweetener attracting the strongest interest, largely because it can be advertised as “natural” and because the existing sweeteners—saccharin, cyclamate, aspartame, Ace-K, neotame, sucralose, and alitame—have been tested and written about for years.

Saccharin was discovered in 1878 in a lab at Johns Hopkins University as a coal-tar extract. Since then it was banned by the FDA on the grounds that it was carcinogenic, and then it was reinstated. Today it’s marketed as Sweet’N Low, is 300 to 500 times as sweet as sugar, and passes through the body undigested.

Cyclamate was discovered in 1937, given the FDA’s approval as GRAS (Generally Recognized as Safe) in 1958, then banned by the FDA in 1969 as carcinogenic. It’s still used in other parts of the planet in, among other things, Coca-Cola Zero, which I enjoyed in Madrid two weeks ago.

Aspartame was discovered in 1965 at G. D. Searle when James M. Schlatter, while working on an ulcer drug, licked his finger and found it sweet, about 200 times sweeter than sugar. Now it’s very successfully marketed as Equal, NutraSweet, and Canderel. Are lab scientists ever supposed to lick their fingers?

Ace-K is short for acesulfame potassium, also discovered fortuitously in 1967 at Hoechst AG, approved by the FDA in 1998, marketed as Sunett and Sweet One, and used mainly in blends.

Sucralose was discovered in 1976, approved by the FDA in 1998, and is 600 times sweeter than sugar. It’s also known as Splenda and by three other brand names I’ve never heard of. Splenda is currently my favorite artificial sweetener because there’s a granulated version for baking (containing an added bulking agent). The minute we had identified a serviceable sugar-free chocolate, we stirred up the batter for my favorite chocolate-chip cookies, substituting Splenda for sugar. The results were nearly acceptable and with a little fiddling would have become a staple treat in our home office, had I not discovered that my assistant Rachel had unaccountably substituted Spenda Blend, which comes in both brown- and white-sugar versions. The blend is half sugar! What a fraud! The thrill of discovery, which I’m sure nearly matched Vasco da Gama’s, melted into thin air.

Made by substituting granulated Splenda for both the white and brown sugars in my recipe, the cookies were regrettable, fluffy and tasteless (no chewiness or caramelization) and no better than the sugar-free cookies you find at the supermarket, which are awful. For the next, and last, version, we added a tablespoon of Walden Farms Pancake Syrup. Like other Walden Farms products, it’s “fat-free,” “sugar-free,” and “calorie-free,” which I thought must be either a misprint or a violation of the Federal Food, Drug, and Cosmetic Act, as amended. How can a whole bottle of syrup have absolutely no calories? The answer was right there on the label: the miracle of cellulose gum. Unlike other Walden Farms creations I’ve sampled, their pancake syrup tastes fine, as long as you don’t insist on real maple syrup. But the improvement in the cookies was insignificant.
 
Our Splenda vanilla ice cream, however, was just short of magnificent. But it was not diet food. Although completely free of sugar (and consequently fine for diabetics not trying to lose weight), a quart of it (measured after churning) included four egg yolks, three-quarters cup each of heavy cream and granulated Splenda, one vanilla bean, and two cups of milk. The texture was good until the ice cream froze solid overnight in the freezer and had to be partially remelted in the refrigerator compartment.
 
Alitame was discovered in the early 1980s as a second generation of aspartame—2,000 times sweeter than sucrose and now approved in Mexico, China, and elsewhere, but not in the United States. Alitame is said to have no aftertaste. The original maker submitted a petition to the FDA, then sold the rights to Danisco, which withdrew the petition. There must be a story here: The absence of a bitter aftertaste is one of the central goals of sweetener chemistry. As alitame was abandoned so quickly, was it responsible for disastrous side effects? Does it make your eyes bleed or your skin turn blue? (Our calls to Danisco were not returned.) If alitame really does have no bitter aftertaste, it is probably the only artificial sweetener that doesn’t. I own a technical volume called Modifying Bitterness. Adding sugar is the easiest way to counteract a bitter taste, but adding sugar is the one thing we can’t try with an artificial, sugar-free, zero-calorie sweetener.

The sweetener sapa was favored by prostitutes in ancient Rome because it whitened their skin (then the height of local fashion) and was thought to be a contraceptive. Prepared by cooking and concentrating grape must (pressed grapes, including skins, seeds, stems, and juice) in lead pans, sapa was full of lead acetate, which gradually poisoned its fans, just as lead pipes and vessels are thought to have played a part in the fall of the Roman Empire. You can read about sapa in Pliny the Elder’s Natural History, Book XXIII, chapter 30.

Neotame, owned by the NutraSweet company, is said to be 13,000 times sweeter than sugar. Thirteen thousand! This doesn’t mean that if you sprinkle a teaspoon of neotame onto your tongue, it will taste 13,000 times sweeter, which in any event is impossible for us to imagine. It does mean that you’ll need to use only one thirteen-thousandth as much neotame to achieve the same sweetening effect as sugar. So, if you dissolve a teaspoon of neotame in your cup of tea, it will taste as sweet as if you had put 143 pounds of sugar in the cup, which is also a ridiculous proposition. Thus I felt that I absolutely needed to taste some. Yet I was unable to score even a little. I telephoned NutraSweet in Chicago, and its CEO, Craig Petray, a reasonable-sounding and modern type of CEO, refused. He told me that neotame was not meant to be eaten straight as a tabletop sweetener and that it is nearly always used in blends. (In the United States, blends usually include only two sweeteners; in Europe, a blend of artificial sweeteners might be composed like a perfume from an entire palette of sweeteners.) CEO Petray conceded that he was worried I might simply eat some neotame out of the bottle, find it repellently bitter, and tell everybody about my sad experience. He did offer to arrange a guided tasting anytime I wanted to visit Chicago. I intend to take him up on it.

Just Like Sugar is promoted as a natural product “that tastes like sugar, cooks like sugar, bakes like sugar, browns like sugar, sauces like sugar, cracks like sugar, caramelizes like sugar” and is free of calories, fat, cholesterol, has a glycemic and triglyceride level of zero, and, thank God, no laxative effect. The main ingredients are chicory root, vitamin C, and orange peel. I couldn’t believe my eyes or ears. I obtained the baking and brown-sugar versions of Just Like Sugar directly from the company, stirred it into my excellent chocolate-chip-cookie batter, added extra water (called for by the company’s Web site to compensate for the amount of fiber in the chicory root), and popped it in the oven. The results were way better than expected, but still short of awesome.

I was surprised that Sky King had rejected the sprig of stevia. He is as omnivorous as any creature I’ve met, so much so that I formulated a theory that dogs—some dogs, at least—descend not from the European wolf, the African hyena, or the Asian jackal but from a cross between a pig and a goat. Why wouldn’t he enjoy the intense sweetness of stevia?

What may have been troubling him was a study carried out in 2008 at Purdue University with three groups of rats. One group was fed a diet of low-fat yogurt, another fed the same yogurt diet flavored with various artificial sweeteners, and the third fed yogurt plus glucose, a mildly sweet, elemental, fully caloric sugar. The result? The rats eating artificially sweetened yogurt gained weight, while the others—even those consuming glucose—compensated for the extra calories by eating less; rats have an enviable mechanism to avoid overeating. The addition of artificial sweetener—in this case, either saccharin or Ace-K—confused the rats’ systems. The guess is that the sweetness on the tongue of an artificial sweetener “promises” that calories are about to enter the digestive system; when they don’t appear, the rats’ adjustment mechanism becomes confused. And when the experiments were over, the fatter rats were unable to lose the weight they had gained.

I’ve been drinking diet soda three times a day for the past 20 years—the entire time I’ve been working from home. I’ve always known it was laughable for me to wash down several slices of deliciously fattening pizza with diet soda, but I figured that, hey, every bit of calorie reduction must do me some good. It looks as though I was wrong, or at least that if I were a rat, I’d have been very wrong. On the other hand, many humans seem to lack a mechanism to compensate elsewhere in their diet (or in their physical activity) for the excess calories they have consumed earlier in the day or week. How can we confuse a system we lack? I have gained weight fairly steadily during these 20 years. The culprit? Is it the diet soda, the fact that I eat for a living, or that between meals I sit at my computer all day?

I’m fairly sure that Sky King lacks any semblance of a regulatory system. He looks so forlorn when he finishes his food, and I have yet to see him stop eating before he has licked his bowl clean, except when I feed him dry dog food. Perhaps that’s why he rejected the stevia sprig. Somewhere deep in his canine consciousness, he knew that the sweet, noncaloric experience would sabotage whatever restraint he still possesses. Another reason could be that Sky King tastes with his nose, not with his tongue, and stevia lacks any aroma. So he doesn’t know it’s food. I will conduct a few more experiments and report back to you.

But first, back to the human world. There is a mystery in America that nobody has been able to solve—the cause of the obesity epidemic, as it is called. Yes, people gain weight when their calories in exceed their energy out. But why have Americans become unable or unwilling to maintain their energy balance?

Chubby people can take comfort in the finding that their tendency to gain weight is genetic. It certainly comforts me. Here’s why. Depending on which study you prefer, the correlation between the adult weight of identical twins raised apart (and therefore eating different food under different conditions) is as high as 80 percent. That’s the genetic part; environmental influences can alter your destiny, but they account for only 20 percent to 40 percent of the final result. And here’s the thing. The average American has gotten fatter and fatter for more than the past quarter-century. Surely our genes haven’t mutated during that time.

So a number of nongenetic factors must be responsible: We get less exercise than even 25 years ago. (Count me in.) We have all stopped smoking. (I went from three packs a day to none. It took ten years of my life, and my weight rose every day.) And have you noticed that portion sizes have swelled beyond control? Both at home and in restaurants, there’s vastly more on the plate, and the plates themselves have doubled in diameter. People eat more of their food outside the home, where there’s no controlling how much they serve you. What’s a person to do?

Except for smoking cessation (which is obviously the main cause of obesity, nationally and internationally), all these other excuses, not to mention the unstemmable popularity of fast food, are completely lame, self-indulgent, and tautological. What we need to find is a dramatic and persuasive evil that accounts for everything. And this, obviously, is the vast soft-drink industry and the sweeteners it uses—particularly, high-fructose corn syrup (HFCS) and, yes, artificial, noncaloric sweeteners.

HFCS has become the dominant sweetener in soft drinks, displacing sucrose. The reason? Predominantly because it’s cheaper. The sharp rise in obesity began just a few years after the introduction of large amounts of HFCS into our diet. Since 1970, the amount of HFCS the average American consumes has increased by more than 1,000 percent, while the percentage of obese Americans has nearly doubled. This, of course, doesn’t prove anything in itself. But there have been other suggestive findings. A paper that appeared at the end of last year in Physiology & Behavior documented another study in which rats were fed a variety of sweeteners and concluded that “even moderate consumption of fructose-containing liquids may lead to the onset of unfavorable changes in the plasma lipid profile,” which means that it raises your bad cholesterol or lowers your good cholesterol, or both. Another study with rats in Switzerland found that long-term “high consumption of fructose in rodents leads to . . . insulin resistance, obesity, type-2 diabetes mellitus, and high blood pressure.” Whew! But the same study conceded that there’s no evidence of a similar effect on humans—except at high doses. While we’re waiting for the votes to come in, I think I’ll avoid all caloric soft drinks. Humans had very little fructose in our diets until HFCS soared in world popularity. It’s just not normal.

And as for artificial sweeteners, I’m persuaded by that experiment showing that rats overate and got fat when they were given artificial sweeteners—which confused their regulatory systems. I am not a rat. And there are no definitive studies on humans. But I, for one, gave up all diet sodas yesterday—right after finishing most of this article. Now I can just sit back and watch the pounds fall away.

Which leaves stevia. It is not artificial—it grows right out of the ground. It is very sweet but has no calories. Maybe that alone will confuse my system and put on the pounds. But stevia also promises a multiplicity of health benefits. What to do?

WOD

Mystery.

Don't post results, only thoughts to comments.