The sizable crowd that gathered for the first Dean's Seminar of the school year was a clear indication that the topic presented by Dr. Jennifer Nasser, assistant professor in the Department of Bioscience and Biotechnology, had piqued some interest: Are your eyes bigger than your stomach?
Engaged in industrial research before coming to Drexel University, Nasser currently teaches and does clinical research, for which she has received funding from the National Institutes of Health (NIH). In her study, Nasser explained the methodologies used to measure light waves in the eye, which are then compared to varying levels of neurotransmitters in thin and heavy individuals. As a nutritionist and dietician, Nasser believes all things, including hunger and self-regulation of food intake, begin at a biological level. "Everything starts with a physiological basis."
Nasser first set out to explain some of the natural ways the human body regulates satiation and satiety or, essentially, hunger and fullness. Our temporal meal pattern, or the body's internal clock, is a significant determinate of when we choose to eat. Circadian patterns and daily routines tremendously impact eating habits.
The macronutrient composition of a meal can also determine how quickly a person will be hungry again after eating. A person eating healthy meals rich in essential nutrients and fiber is likely to remain satisfied longer than someone consuming junk food.
Each person has his own gastric capacity, which determines when he feels full or hungry. When this point is reached, neurological signals are sent to the brain, particularly to the hypothalamus or "pleasure center," which tells the body it is time to stop eating. This gut peptide-brain interaction is one of the essential elements in Nasser's research.
Psychological and environment factors, however, often throw a wrench into this system of regulation. People tend to eat the foods that are proximate to them. For instance, it is not unlikely that someone would opt for ice cream sitting in the freezer before walking five blocks to order a salad. Many people follow this "see food and eat it" diet, Nasser joked.
Social learning and socialization frequently hinder control of food consumption as well. If a child grows up in an environment where fast food is endorsed and vegetables are rare at meals, chances are this child will continue eating unhealthily into adulthood. These days, the social pressure to eat can get overwhelming, and in various situations, food can serve as a social lubricant. Rituals like sporting events or holiday gatherings often center on food. "On Thanksgiving after you've already eaten a whole meal, out comes Grandma with the whipped cream and pumpkin pie. Who can say no to Grandma?"
Extreme emotions and high stress levels can be positively correlated in individuals who overeat. Some studies indicate that cortisol, a stress hormone, can cause an increase in appetite. People may tend to over- or under-eat if they possess a dominant personality trait such as restraint or impulsivity, which are heavily associated with eating disorders such as anorexia and bulimia.
Before delving into the details of her own research, Nasser described a few outside experiments where habits and tendencies of the lean and obese were compared. One study of particular interest asked: Does being fed or not fed have any impact on memory? In this study, 26 people, both thin and heavy, were asked to fast for a short period of time. They were then interviewed and asked to complete tasks involving memory. The data came back similarly for lean and obese folks in the control phase of this experiment. However, next time everybody was given a milkshake before the interview and evaluation. Results showed that hippocampus activity increased in a lean person and decreased in a heavy person when in the "fed" state. It seems certain that hunger and brain functionality are interrelated.
Nasser's research begins with the idea of sensory convergence. Behind the eyes, nerve endings implicated in vision, touch, and olfaction come together. This convergence led Nasser to suspect a connection between the eyes and the stomach. Dopamine, a neurotransmitter naturally produced by the body, is the central experimental element in her research. Dopamine has been called "the feel-good drug," and is associated with reward-seeking behavior. Because dopamine is one of the neurotransmitters essential for visual functioning, an electroretinogram (ERG) was given to the subjects in conjunction with increased levels of dopamine. An ERG measures electrical responses to light and wavelengths in the eye. Nasser wanted to learn whether the ERG results would show increased amplitude in wavelength with the consumption of food because of the increased dopamine levels.
Male and female subjects ranging from 18 to 50 were administered 10 milligrams and 20 milligrams of Ritalin, a drug containing dopamine, and a brownie, in three separate trials. As Nasser expected, the ERG results indicated an increase in wavelength when obese subjects were given the brownie and the higher dose of Ritalin (both producing greater levels of dopamine). Not only was the wave amplitude greater in heavier subjects, but the increase occurred sooner after receiving the brownie than in thin subjects. This preliminary data provides Nasser with a basis to further her research and continue clinical trials.
The relevance placed on food consumption and eating habits is virtually undeniable in American culture. Weight gain and obesity are universally troublesome, their effects felt by men, women, and children of all ages. Nasser used her extensive knowledge and impressive research experience to engagingly illuminate the chemical and biological factors affecting food consumption and obesity. In summation, Nasser said, "In obese humans, it seems the eyes may at least be as big as the stomach."
