Reward Swapping


We’ve long understood that smell is a major component of taste, but it turns out it’s also an important element of the reward system. New research points to a novel and simple method to exploit this connection and help you reduce your cravings for unhealthy foods.

Your nose leads the way

Previous research in mice has shown that hunger stimulates the endocannabinoid system to increase their sense of smell and help them locate food. Humans have a similar system, but since our sense of smell is much weaker, we tend to process this increased olfactory connection on a more subconscious level. It still seems to have an impact on appetite and obesity.

Obesity and impaired sense of smell

Researchers from the University of Otago in New Zealand examined over 1400 individuals across 38 scientific papers that covered the topic body weight and sense of smell. They found that obese patients had an impaired sense of smell and that bariatric surgery patients that lost significant body weight actually reversed their olfactory decline.

Another study of obese women found that the impairment of the sense of smell is caused by chronically high levels of circulating endocannabinoids in their systems. Unfortunately, these same endocannabinoids are also associated with increased appetite. A diminished sense of smell combined with increased hunger leads many to avoid blandly-scented, “healthy” foods in favor of more strongly-scented junk foods like bacon, Doritos and cookies.

Combining your five senses

As I mentioned above, scent is actually a big part of taste and that interplay between our senses was the focus of the new study from researchers at the University of South Florida. They were examining the concept of cross-modal sensory compensation. Our five senses don’t operate independently, but rather they have been shown to converge in certain regions of the brain so the incoming data can be combined and properly interpreted. Sensory information for scent and taste is processed in the same area of the brain, which is why they are so closely related.


Cues and rewards

One of the more interesting aspects of the study (and prior supporting research) is that the reward centers of the brain are stimulated before you actually eat “indulgent” food sources (those high in sugar and fat). This means that dopamine starts building up in the brain as a reward when you smell indulgent foods like cookies and pizza, or even when you see a picture of them.

These are learned associations. Your body was previously rewarded by the high calorie combo of sugar and fat and associated it with those scents or images. So when you are exposed to them again, the reward system can start kicking in before you actually eat them.

The newest study wanted to examine if you could receive your indulgent reward from scent cues alone, and then make healthier, less calorie-dense choices when it’s actually time to eat.

The experiments

The researchers conducted two experiments:

  1. They used an air nebulizer to inconspicuously scent the air in a middle school cafeteria with the indulgent scent of pizza or the healthy scent of apples. They categorized the available items for sale at the cafeteria as healthy or unhealthy and then measured the quantities of items purchased each day. On the control day with no scent and the healthy day with the scent of apples, of the 2800 items sold, about 1050 were unhealthy. On the indulgent pizza-scented day, of the 2900 items sold, only 628 were unhealthy.

  2. For the second experiment, they brought subjects into the research lab and used the same nebulizer to expose them to either a strawberry or cookie scent. The purpose of this test was to see if exposure time made a difference. They offered the test subjects the choice of the indulgent cookies or the healthier strawberries. They wanted the scents to match the food options available to really test the priming effects of the reward system. They found that after 30 seconds of exposure to the cookie scent, it increased people’s desire for a cookie, but an exposure time of 2 minutes or greater led to a higher preference for the strawberries.


Two big take-aways

This research highlights two simple things anyone can incorporate to help control their appetite and reduce cravings for unhealthy foods:

1. Take your time (you have more than you think)

Many people over the years have recommended slowing down and increasing your “mindfulness” during each meal to decrease the quantity of food consumed. Most people think of it as a trick to just increase the time between bites, but the research above explains how it can reduce your desire to over-indulge. By slowing down and taking time to absorb the scents and activate your reward systems, you can increase your self-control and preference for healthier options. Unlike a lot of suggestions out there, it’s not about trying to test your willpower and deprive yourself. Simply enjoying the scent of your meals can increase the feelings of reward and enjoyment before you even taste it. If you activate your reward systems before taking your first bite, you won’t need nearly as many bites to feel satisfied. This can also be another reason why cooking at home can help you better control your weight.

2. Get spicy

On the subject of home cooking, when you do prepare your meals, really spice them up to increase the ambient scents. If you’re trying to lose a significant amount of weight, it’s possible that your sense of smell is impaired. Crank up the spices to increase the scent and cut through to your reward centers. Spices like garlic, oregano, basil, cayenne pepper, onion, cinnamon, sage and turmeric aren’t just fragrant, they offer incredible health benefits. Many offer anti-cancer, anti-inflammatory, and immune boosting benefits so feel free to pour them on thick to anything your eat.

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