Taste and smell -- they makes us hungry and tell our brains what might be good to eat.
But one doctor has said that manipulating the smell and taste of food can fool a person's brain and stomach, and that's the key to dropping pounds in his new weight-loss regimen, which he says is scientifically proven.
Dr. Alan Hirsch, a neurologist and psychiatrist, has invented food flakes made of assorted salty and sweet flavorings and minerals, from maltodextrin to silica. Sprinkle them on everything you eat and, he said, they enhance the flavor of your food, making you feel full faster and stop eating sooner.
He has been promoting this idea for years. Back in 2004, his product was called Sprinkle Thin and the ads made bold weight loss claims, such as "clinically proven to help lose weight."
Sprinkle Thin was not long for the market and went out of business in 2005.
But now it's back.
Now called Sensa, the product's new ads quote women saying Sensa helped them get the bodies they wanted. But even with all the hype, it's still virtually the same flavor flakes -- but with a new name and even bolder claims.
Now the flakes are billed as "a scientific breakthrough helping thousands of men and women take back control over food."
So, what's the scientific breakthrough? Six weeks ago, Hirsch presented the results from his study on Sensa sprinkles at the prestigious Endocrine Society's annual meeting. Among the findings of a 1,500-person study was an average weight loss of 30 pounds over six months-- an impressive claim.
Hirsch says the diet is different from others online or in bookstores because his work on weight loss is scientifically proven. He claims to have the endorsement of his colleagues in the form of the gold standard of medical breakthroughs -- peer review.
That is a crucial claim, because to most scientists, peer review is an important scientific term. It means his study has been examined by other experts in his field and endorsed as good science, and that his findings have been published in a reputable medical journal.
But was Sensa peer-reviewed?
"20/20" showed Hirsch's study to professor Barker Bausell at the University of Maryland. He is one of the nation's foremost authorities on clinical studies and the author of a book on medical exaggeration.
Bausell said that Hirsch's research "has a negative value." It hasn't been published in a major medical journal, although Hirsch says it will be.
"It takes a long time after you complete studies to go through all the data analysis and write it," Hirsch said.
But the Endocrine Society, which Hirsh says reviewed and approved of his work, said they merely invited him to present his findings for debate. And they were "surprised and troubled by the promotional nature of his presentation."
Dr. Pamela Peeke, a clinical professor of medicine at the University of Maryland and the host of Fit for Life, says there is no scientific proof that Sensa works and believes the study was done to justify a commercial product.
"There's no magic bullet and there's no magic sprinkle," she said. "This isn't a diet. This is just another pet rock."
Hirsch said he would eventually have a finalized study that a journal would accept, but in the meantime he cannot turn his back on people who need to lose weight.
"When you talk to patients who've lost 30, 40, 50 pounds and you see and talk to them and they call you back and they say, gee you know their life has changed, it's a wonderful thing," he said, "and it's really not fair not to let people have this."
Hirsch provided "20/20" with a handful of happy customers, including one man who claimed he lost 120 pounds.
"You know there is a very interesting plaque I once saw at the National Institutes of Health," Peeke said. "It said in God we trust, everyone else must show data. People believe what they want to believe."
Especially when the people in the Hirsch study weighed themselves and reported their own weight losses with no outside checks.
"When you cannot monitor and supervise participants in a trial, that's a big problem because people will report what people will report," Peeke said.
When pressed, Hirsch did acknowledge some mistakes in the selling of the scientifically unproven Sensa flavor flakes. First, the promotional video falsely claims a control group used fake flakes to compare how much weight they lost versus those given actual Sensa.
"That's something the distribution company did," Hirsch said. "That's not something I did. Obviously a misunderstanding."
Peeke and Bausell also told "20/20" that Hirsch used an ingenious marketing ploy.
While most clinical studies pay the participants for their time and effort, Hirsch actually asked his participants to pay him $49 a month, a notion that made Bausell laugh out loud.
"It's a double-dipping situation," he said. "I mean, it's really genius." But Hirsch says it happens all the time, and that the U.S. Food and Drug Administration approves of the practice.
"At the end of the day, doing this study was not something we made money from," he said, adding that Sensa broke even.
"20/20" found four people who said they lost weight as part of Hirsh's studies and they had one thing in common. Afterwards, none of them kept the weight off. "My experience with the sprinkles for me, it really didn't work," according to one study participant.
Others said the weight came back once they stopped using the flakes. But once the study's over, Hirsch said, it's over.
"There are different things that could've made the study more elegant," he said. "Bottom line is people lost 30 pounds in six months."
At least-- they say they did.