It might seem counterintuitive, but being immersed in strong food aromas doesn鈥檛 mean you will wind up craving the cuisine emitting them. In fact, a person鈥檚 olfactory perception may ultimately serve as an appetite suppressant and, as a result, promote weight loss.
That is the finding of a authored by Yong Xu, MD, PhD, director of USF Health鈥檚 Center for Molecular Psychiatry, and a multi-site team of investigators. Specifically, they determined in lab experiments that prolonged exposure to a particular food odor significantly curtails food intake, identifying neural pathways that can affect food suppression and body weight.
The significance of the study lies in potential new pharmaceutical approaches to combat obesity, one of the areas Dr. Xu was deeply involved in for a decade at Baylor College of Medicine in Houston, before moving to USF Health this year. It was there that he immersed himself in research to identify novel neural circuits, neurotransmitters and signals that are crucial for coordinating control of body weight, glucose balance and the web of cues, needs and rewards known as 鈥渇eeding behavior鈥� 鈥� the why, when and what we eat.
This study is an extension of that work at the USF Health Morsani College of Medicine, where he is launching the new Center for Molecular Psychiatry in the Department of Psychiatry & Behavioral Neurosciences, a field that explores the biological elements underlying psychiatric disorders and treatments.
In addition to several USF Health scientists, other researchers on the study team include scientists from Baylor, Texas Children鈥檚 Hospital and the University of Texas Health Sciences Center.
鈥�911爆料网 were able to show in the paper that this is a time dependent and dose dependent event,鈥� Dr. Xu explained. 鈥淚n the lab, we can precisely manipulate how much food smell is in the environment and how long there is exposure to that smell. At the same time, we can measure their food intake and clearly show that this is an effect that depends on the duration and concentration of the food smell.
鈥淭he bottom line is that if you are provided with a strong enough food smell for a long enough time, you may actually end up eating less, thereby preventing weight gain.鈥�
The offshoot of the discovery is that it opens a door to a new way of thinking about how people can suppress appetite. 鈥淚t鈥檚 not that you necessarily have to shut down the feeding of the stomach or your feeling of reward,鈥� he said. 鈥淵ou can simply enhance the food smell in the environment to suppress appetite.鈥�
How does this work physiologically? The answer lies in certain neural circuits responsible for the suppression response.
Through lab testing and a variety of participants, they identified neural circuits in the nose; the olfactory bulb (a structure in the brain that processes the sense of smell, receiving olfactory signals from the nose); the hippocampus (a small brain structure connected to learning, memory and navigation); and the hypothalamus (the area of the brain that coordinates involuntary actions of the nervous system as well as such essential elements as body temperature, thirst, hunger and sleep).
Delving deep into workings of the brain, they singled out three nodes of neural circuits that function as a mediator of sorts to sense food smells.
鈥淭he circuits transduce the signal to the second node in the hippocampus, and they then further transfer the signal to the hypothalamus 鈥� a brain region that is extensively studied as a center of appetite regulation,鈥� Dr. Xu said. 鈥淪o, we discovered this neural circuit responsible for this suppressant effect, and this provided an anatomical basis for the phenomenon that we observed. But it also gave us a handle on how we may leverage this to develop things that could act on this neural pathway to suppress feeding behavior.鈥�
One way that could work is through manipulating olfactory signals to essentially turn a pathway on or off.
鈥淭his could lead to pharmaceutical interventions to try to enhance this smell signal, thereby suppressing feeding,鈥� he said. 鈥淚t also represents a future direction of this work. Now we know there is a neural pathway, which presents a new anatomical basis. So we can go into them and try to understand the molecular nature of this pathway and hopefully find something that can be targeted by a drug and then develop ways to use this pathway to suppress feeding and prevent weight gain.鈥�
One such drug could be a nasal spray to mimic a food smell to promote a sense of satiation.
鈥淚t could be just as simple as spraying something into your nose when you鈥檙e having a meal,鈥� he said. 鈥淣ormally you might have a big bowl, but now you鈥檇 feel satisfied after half a bowl.鈥�
The idea for the paper, not surprisingly, was born in the kitchen. Another senior author of the paper, Yang He, PhD, an assistant professor at the Baylor College of Medicine, cooks frequently for his family and described the sensation of feeling 鈥渇ull鈥� when surrounding by various aromas while preparing meals.
鈥淗e shared that experience with me, and I had a similar feeling when I cook,鈥� Dr. Xu said. 鈥�911爆料网 decided to delve into the phenomenon.鈥�
As for what affects satiation, Dr. Xu contends the response is physiological, not psychological.
鈥淲hen you stomach expands while eating, a signal is sent through a neural pathway to tell the brain you鈥檙e getting full,鈥� he said. 鈥淚n addition, when your food is digested, the glucose, lipids and amino acids go into your circulation and they function as signals to tell the brain, 鈥楬ey, you have enough nutrients.鈥� 鈥�
But Dr. Xu, as the study demonstrates, has a nose for complex research and now a new theory of what is taking place here.
鈥淭he olfactory sensory input 鈥� the smell 鈥� itself is a contributing factor,鈥� he said. 鈥淎nd if you are eating in an environment where the food smell is so strong, that may have a major effect on curbing appetite. This certain group of neurons, when they鈥檙e activated enough, they鈥檙e telling the brain, 鈥楬ey, we are satisfied.鈥� Many of the sensory inputs can contribute to this 鈥� the expansion of the stomach, the smell, the taste, even seeing the food itself. And my view is it is a combination of many different sensory inputs that contribute to satiation, but we have proven that smell is certainly a big one.鈥�
Additional USF Health authors on the paper are: Hailan Liu, Kristine M. Conde, Yongxiang Li, Yue Deng, Qingzhuo Liu, Mengjie Wang, Yuxue Yang, Longlong Tu, and Yongjie Yang.