The human appetite is a fickle thing. It may come on strong if you walk by a hot dog stand but disappear if you spend too much time thinking about the ingredients. Comfort eaters may feel ravenous at the end of a bad day. And people who are bored with what they're eating may feel full (or at least fed up) after just a few bites.
At a time when so many people are struggling with their weight, appetite has become a hot topic. Researchers work to understand its ebb and flow, and dieters look for ways to dial it back.
Lots of appetite suppressants have hit the market over the years. One recent example that's making the rounds on TV commercials is a powder called Sensa, It supposedly turns off appetite without any drugs or stimulants when users simply sprinkle it on their foods. Each packet or "shaker" of Sensa contains a formula for savory foods and another for sweet foods. Cereal in the morning, a burger with fries at lunch, tuna casserole surprise at dinner — everything is supposed to get a fine dusting.
According to the company website, Sensa wakens a user's senses by subtly enhancing the smell and taste of food. The powder is said to activate the olfactory (smell-sensing) part of the brain that helps control appetite. With their noses and taste buds on high alert, users supposedly feel full after just a few bites of food.
Sensa crystals contain the sugar maltodextrin along with natural and artificial flavors and, in some cases, soy and milk extracts. Because the serving sizes are so small, the product is technically sugar-free and calorie-free. The six-month system comes with six packages, each with a slightly different formula. According to the company, switching up the formulas each month keeps the senses from getting complacent.
Sensa is sold online and at GNC stores. Shopping on the company site, you can buy a six-month supply (along with a "getting started" DVD) for $289.
A TV ad for Sensa calls it "a revolutionary weight loss system that will change your life." Users are assured that they can "eat what [they] like and still lose weight." How much? One woman in the ad claims to have lost 50 pounds, and another says she lost 45.
Dr. Alan Hirsch, creator of Sensa and founder of the Smell & Taste Treatment and Research Foundation, a Chicago treatment center for people with smell and taste disorders, says that Sensa is clinically proven to work. He conducted a study of 1,436 subjects (mainly women) who used the Sensa program for six months. The study hasn't been published in a medical journal, but it was presented at a meeting of the Endocrine Society in 2008. In the study, Sensa users reportedly lost an average of 30.5 pounds or almost 15% of their body weight. One hundred people who sprinkled fake Sensa on their foods reportedly lost only 2 pounds on average.
The bottom line
There's no doubt that flavors and aromas can have a huge effect on appetite. And there's good evidence that enhancing the smells of foods really can make people feel fuller while eating less. A Dutch study published last year, to name one example, found that subjects ate less strawberry yogurt if it was infused with a rich strawberry scent.
But there's a credibility gap between such research and the results promised by Sensa, says Adam Drewnowski, director of the nutritional sciences program at the University of Washington in Seattle and a renowned expert on taste, appetite and obesity. Because the Sensa study wasn't published in a peer-reviewed journal, many questions about the design and the results remain unanswered. Among other things, he says, it's impossible to know how the subjects were selected, how they were weighed and the range of weights that they lost. "Did some people lose zero pounds?" he asks. "Who knows?"
More fundamentally, Drewnowski doesn't see how the product could work as advertised. There's no evidence that small amounts of maltodextrin or any blend of "artificial and natural flavors" have dramatic effects on appetite, he says. "There are no active ingredients." If there are any, he adds, "they aren't showing up on the label." The strawberry study and similar research show that enhancing specific flavors can blunt appetite, but he knows of no substances or flavors that would work on a wide variety of foods.
The huge amount of weight that users can supposedly lose with the help of Sensa in just six months strains credulity, says Dr. Marc-Andre Cornier, an associate professor of medicine in the department of endocrinology, metabolism and diabetes at the University of Colorado Denver . "Losing 15% of your body weight — that's usually what we see from gastric bypass surgery," he says. "I'm extremely skeptical." People who are committed to diet and exercise may be able to lose that much weight on thier own, but Cornier says it's highly unlikely that such dramatic results can come in a package.
Hirsch responds that Sensa probably doesn't deserve all of the credit for the "very substantial" weight loss seen in the study. It's possible, he says, that, in addition to blunting appetite, Sensa made people more aware of their food and motivated them to watch their diets and get more exercise. "I always tell patients that the best way to lose weight is to exercise, but they never listen to me," he says.
On the plus side, Sensa looks to be completely safe, Cornier says. Dieters who gave it a try wouldn't be risking more than a few hundred dollars. And if they didn't get any results from their investment, they wouldn't be the first.
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