“I want to talk about how people make choices,” he said, “both for now and for the future; and how to delay immediate gratification for the long term.”
We eat for two reasons: to keep our bodies stable and for pleasure. The “reinforcing value” of food describes how hard someone will work to get access to it.
“Food is a powerful reinforcer,” Epstein said. “In animal models, it’s even more powerful than heroin and cocaine…and it’s strongest in food with a high sugar content.
“Babies respond right away to a sweet reward,” he continued. “It’s built into the limbic system”—a collection of deep brain structures common to all mammals.
The human infant’s brain already has a dopamine reward system that confirms milk is sweet and delicious. Dopamine is a versatile brain chemical that plays many roles, including how we register and reinforce pleasure.
So infants know how to eat, but learning to delay gratification comes much later. The prefrontal cortex (the front of the brain) is vital for “executive function” including long-term planning, judgment and self-control. And it’s not fully developed until the mid-twenties, so “a 12-year-old may not have the cognitive apparatus necessary to resist.”
Epstein illustrated this concept with a video clip of the famed Stanford “marshmallow experiment” in which young children were offered a choice: a single treat immediately or multiple treats if they were able to wait.
The sight of children with a tempting snack was endearing and funny, yet the implications were bracing. Follow-up studies found that, in general, children unable to wait grew up to be “more obese, had more contact with the criminal justice system and less education...”
Everybody wants immediate gratification, but some people have a harder time than others in resisting their impulses. Epstein has seen a connection between impulsivity and differences in the prefrontal cortex, visible on brain-imaging studies.
Epstein proved to be an engaging speaker at NIH.
Photos: Ernie Branson
In an automotive metaphor, he called this “leadfoot and worn brakes.”
“Obese people become sensitized [to high-calorie foods],” he explained, “so the more you eat, the more reinforcing it becomes.”
If you eat sweets over and over, the brain’s reward system creates the craving for more—what Epstein calls “reinforcement pathology.” This pathology, he said, is the interaction of the reinforcing value of food (lead foot) with the inability to delay gratification (worn brakes).
As a result, overweight and obese people have a harder time shifting their attention from current to long-term rewards. Epstein calls this “delay discounting”—our human tendency to discount, or undervalue, the merits of waiting.
Anyone, especially children, can act in haste, without thinking decisions through. Too much delay discounting is associated with overeating, over-shopping, drinking too much, abusing drugs and gambling.
Here’s the good news: “Now we can teach people how to reduce delay discounting, where they learn how to mentally simulate the future in order to moderate present behavior...We do this all the time. Before I came here, I said to myself as I was putting the slides together, which are people going to like?”
Epstein has refined and quantified this as episodic future thinking (EFT).
EFT teaches people to think about a long-term goal or event they are looking forward to by encouraging them to visualize a future event.
“The effect depends on how vividly they imagine and how positive the event is,” said Epstein. Interestingly, “none [of the visualizations our subjects chose] were food-related.”
Subjects also used “tags,” or cues to initiate the EFT, such as moving their watch to the opposite wrist—to remind them to focus.
Athletes who are using visualization techniques to improve their performance, he said, “basically do a variation of EFT…Whatever the possibility is, they play it over and over in their minds, exactly the thing we’re talking about, only we’re putting it into practice for health behavior change.”
During the discussion, Epstein agreed on the importance of exercise in memory training: “Think how much executive function a [basketball] point guard has to have. Sports require a lot of self-regulation, planning, cognitive flexibility and working memory.”
In his earlier work, Epstein showed how overweight and obese women can become equally capable of the impulse control that lean women exhibit.
His current research involving mentally simulating future events is positive news for people who have struggled to lose weight.
“It shows that when people are taught to imagine, or simulate the future, they can improve their ability to delay gratification.”
And he’s optimistic about the future: “We’re doing our first field study…People are going into the college cafeteria, and right before they purchase, they listen to their tags. It’s really had a big effect on people’s ability to regulate their eating. We plan to follow this up with a clinical trial using EFT as a component of family-based treatment for pediatric obesity.”
A videotape of Epstein’s talk is available at http://videocast.nih.gov/summary.asp?Live=13881&bhcp=1.