Here is the NY Times, describing the latest weight-loss fad:
Like almost every dieter in America, Wendy Bassett has used all sorts of weight-loss products. Nothing worked, she said, until she tried Sensa: granules she scatters on almost everything she eats, and which are supposed to make dieters less hungry by enhancing the smell and taste of food.The maker of Sensa claims that its effectiveness is largely related to smell: the heightened scent and flavor of food that has been sprinkled with Sensa stimulate the olfactory bulb -- the organ that transmits smell from the nose to the brain -- to signal the "satiety center" of the hypothalamus. Hormones that suppress appetite are then released.
Unfortunately, I think Sensa's approach is exactly backwards. Delicious smells are what psychologists refer to as a "hot stimulus," a sensory provocation that makes us want to eat. I described this process in my recent New Yorker article on Walter Mischel and the marshmallow task, a simple experiment in which four-year olds attempt to not eat the tempting treat right in front of them. The question, of course, is why only some children are able to resist, while others gobble down the marshmallows (or oreo cookies) in less than thirty seconds:
Mischel's conclusion, based on hundreds of hours of observation, was that the crucial skill was the "strategic allocation of attention." Instead of getting obsessed with the marshmallow--the "hot stimulus"--the patient children distracted themselves by covering their eyes, pretending to play hide-and-seek underneath the desk, or singing songs from "Sesame Street." Their desire wasn't defeated--it was merely forgotten. "If you're thinking about the marshmallow and how delicious it is, then you're going to eat it," Mischel says. "The key is to avoid thinking about it in the first place."
The problem with Sensa is that it makes it harder to not think about food - we can't strategically allocate our attention because those delicious smells keep on reminding us how hungry we are. If anybody loses weight on Sensa, I'm betting that it's placebo effect at work, and not some hypothalamic pathway.
This nasal product, though, seems much more promising.
Brain & Behavior
Comments (18)
Seth Roberts has an interesting theory about this. We know that the body has a set-point for weight and the body eventually bounces back to this set-point. Roberts accidentally found a way to hack the set-point and has a quite convincing theory about the big picture. His diet is called Shangri-la Diet.
It is described here:
http://sethroberts.net/science/index.html
I'll try to summarize the idea here. So the idea is that we maintain this flavor-calorie association. After we've eaten a particular taste a few times, our brains automatically learns to associate the taste with the calories it gives. A simple example: an adult who has never tasted Coca-Cola will find the taste awkward, but will learn to like it really quickly, because of the calorie association.
Now, the hypothesis is that the set-point is adjusted by "estimating" how much food is available. When there is not a lot of food available (tastes are not rich), body drops the set-point to live off the body fat already accumulated. In contrast, when there is plenty of calorie-rich food, it is time to store the food and thus body adjusts the set-point higher and generates more hunger.
This is why modern pre-packaged and standardized food leads so easily to obesity: it develops such a strong flavor-calorie association, because the flavor stays constant and the food is calorie-rich. And this is also why most diets do work for a while. When a person starts a diet, he will typically experience new flavors that do not have such tight association with calories. But once the connection is made, the diet no longer works.
But what Roberts accidentally found is that consuming completely flavorless calories lowers the set-point. Consuming flavorless [1] olive oil, for example, in a way simulates this sort of "flavorless non-rich food times" and body lowers the set-point. The set-point is not lowered by that much, because you do eat normal food. But because the set-point is lowered, losing weight becomes pretty much automatic. The body generates just enough hunger so that the set-point is reached. (And this is of course why normal dieting is so hard: it's almost impossible to fight against the set-point.)
All that said, the method doesn't seem to work for everyone. The reason for this is not known. Also, it hasn't been tested with double-blind placebo-controlled studies.
Coming back to the "Sensa" method, I think Roberts's theory says that it shouldn't work. It should probably make it harder to lose weight. It might have this initial effect of introducing new flavors to the people using it, so they wouldn't have such strong flavor-calorie associations at start.
[1] Flavorless means that the oil itself doesn't have flavor, but also that it is consumed as such, not with other food. In fact, it is recommended to not eat anything with flavor at least an hour before and after consuming the oil.
Posted by: Jarno Virtanen | June 19, 2009 10:49 AM