Could how heavy you are correlate to how strongly your brain reacts to the scent of bread wafting from a nearby bakery or backyard BBQ? Studies show that your senses (like smell and taste) react to inputs from the world around you, and not everyone’s neurobiological reactions are the same.

Despite decades of research, the truth is that scientists don’t exactly know why some people are overweight or obese, and some people aren’t. What we do know is that it’s not just about caloric intake, or activity level (though both do have some impact), and it’s not just about your genes. It’s mostly not about the type of food you eat, as carb-rich diets vs. protein-rich diets have generally been found to be equally unsuccessful for long-term weight loss (although processed foods — which tend to be carbs — definitely contribute to weight gain). And it’s not just about your psychology, or about how you were parented, though certainly family eating style is relevant.

It definitely *is* about how all of these things come together; calories in, activity level, metabolism as determined by genes, family eating, and brain chemistry.

All of which makes finding a ‘cure’ for obesity problematic. Rising levels of overweight kids and adults in the United States (and around the world; Northern and Western European countries both have rates of obesity around the same as ours) prove that nothing tried so far is working. And with chubby kids much more likely to grow up to become adults who are heavy, this is an issue that’s not going away.

But some studies point to the idea that different people deal with sensory inputs in various ways and may give us insight into some of the triggers of overeating, which is still at the heart of the issue for most overweight people.

An experiment at Maastricht University in The Netherlands shows us that there are some fundamental differences between overweight and normal-weight children’s caloric intake after exposure to the smell and taste of food. In the 2003 experiment, children were exposed to tasty smelling food for ten minutes, and then given food to eat; the normal weight kids tended to eat less than they would have if they hadn’t smelled the food first, which means they were at least partially satisfied just by enjoying the aroma of the food. On the other hand, the overweight kids actually ate more food after the exposure to delicious smells. The same went for if the kids were given a small snack beforehand.

What does this data mean?

First of all, is shows that overweight children eat normal amounts when tempting food cues are lacking. But when the overweight children are tempted by the taste or intense smell of tasty food, they eat more than normal-weight kids and thus fail to regulate their intake. In other words, overweight children are more vulnerable to triggers of over-eating (great smelling and tasting food).

Looking at the data from the flipside (how to help those with eating disorders): Olfactory stimulation has been found to be a remarkable tool in stimulating appetite. In a 2010 study out of the European Centre for Brain Research in Rome, scientists experimented on rats, which have a very strong olfactory response, and found they were able to get the rats to seek out chocolate by ‘priming’ them with the scent of chocolate. Even rats that were already full from eating other foods would present cues that they were hungry when they smelled milk chocolate.

“…The present results strongly suggest that smell is a crucial factor in the treatment of eating disorders,” though according to the researchers, it hasn’t been studied much yet in human beings.

At the end of the day, we still do have choices to make (and here I am NOT suggesting that heavier people lack willpower!) and education is key while scientists continue to sort out what combination of mechanisms are responsible for overweight. As a 2006 report from Purdue University in Indiana published in the journal Obesity notes, “The decisions about what, when, where, and how much to eat are guided by inherent responses but, more importantly, acquired knowledge.”

If some of us get completely and utterly distracted by the always-tantalizing smell of freshly baked bread, desserts, (I do!) or other foods while others can breeze on by with barely an acknowledgment, that just means that those of us with heightened senses just have to learn how we are different, and how to modify our behavior when confronted with temptations.

Starre Vartan is known in the webiverse as the Eco Chick as she has been blogging at a site by the same name since 2005, and authored a spin-off book, The Eco Chick Guide to Life. She covers science, technology, the environment, fashion & lifestyle (and has no qualms about the combination thereof).

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