While Thanksgiving and other festive holidays are special occasions for gorging, many patients with a certain form of dementia are compelled to stuff themselves routinely.
Josh Woolley, MD, PhD, a medical resident in psychiatry at the UCSF Memory and Aging Clinic, is studying overeating in patients with frontotemporal dementia (FTD). Repeatedly, patients keep eating, even after they say they are full. Woolley wants to understand why the behavior arises and persists. What Woolley learns might also shed light on why the rest of us overeat, as well.
“Overeating is a major problem among the general population,” Woolley says. “It’s rapidly gaining on cigarette smoking as a major cause of mortality. Very little is known about why people overeat. FTD is a disease in which parts of the brain atrophy and it leads to compulsive overeating.”
“I’m hoping we might learn something about the brain circuitry involved, and about why people overeat in general.”
FTD is distinct from Alzheimer’s disease, although both steadily worsen over time. Individuals with FTD often lack normal inhibitions, make bad decisions, act in socially inappropriate ways and overeat. They do not typically lose their memories.
“Different parts of the brain are affected in Alzheimer’s disease and FTD, and the two disorders have different symptoms,” Woolley explains. Even among FTD patients, different parts of the brain’s frontal or temporal lobes may atrophy, leading to different behavioral symptoms.
The study is part of a major FTD research program funded by the National Institutes of Health. Bruce L. Miller, MD, clinical director of the Memory and Aging Clinic, leads the overall research effort. Woolley works in collaboration with Miller and Katherine Rankin, PhD, a Memory and Aging Clinic neuropsychologist.
Brain Atrophy and Binge Eating in FTD
Study participants were in their fifties and were suffering from various neurodegenerative diseases, including FTD and Alzheimer’s disease. Their spouses also were included in the study as healthy controls. Patients were evaluated with brain imaging, as well as with cognitive and language tests. Patients and their spouses lived at UCSF’s General Clinical Research Center for a week.
For those of us without dementia, scientists have obtained evidence that when a greater amount and variety of food is set before us, many of us do indeed often eat more than we would otherwise.
In the dementia study, 75 patients and their spouses were randomly assigned to two different all-you-care-to-eat lunch options on two different days. On one day, patients were offered as much as they wanted of seven different sandwiches. On the other day, they were offered as much as they wanted of just one type of sandwich of their choosing. A constant volume of food was kept on the tables.
Almost half of the patients with FTD spontaneously reported feeling full but nonetheless continued to eat.
“One of the patients ate 10 sandwiches in an hour even though he reported feeling full after only 2 sandwiches” Woolley says. “The patient knew he was full, but he did not stop eating.”
In general, patients with FTD overate, and they were more likely to overeat when offered a variety.
“You’re not full because your stomach is physically full,” Woolley explains. “You’re full because your brain tells you not to eat any more. The message can be turned on and off, depending on the food available.
“You may eat turkey at Thanksgiving until you feel completely full, but then out comes the pumpkin pie – with some different sensory qualities – and suddenly you’re not full anymore.”
The six FTD patients who ate the most had the greatest amount of atrophy in brain circuitry in regions called the insula and the basal ganglia. The insula is deep inside the brain, within the fissure separating the frontal and temporal lobes. Bodily sensations map to it, including sensations from the gut. So does smell. The basal ganglia and insula are thought to integrate information about body sense with decision-making.
If these circuits are damaged, it might lead to a decision to overeat, even when gut sensations or hormonal messages normally might cue one to turn down that last helping, Woolley says.
“I would argue that these circuits are important for resisting cues to eat,” Woolley says – cues such as an abundance of available, tasty food.
“What was surprising was that patients who were overeating were not heavier than those who weren’t overeating,” he adds. Plenty of other mysteries remain.
Woolley now is analyzing blood from the study participants. He’s measuring hormones that affect hunger or satiety, such as insulin, ghrelin and leptin. He wants to know if the overeaters are getting hormonal signals for fullness. If the answer is yes, then he wants to learn exactly what is going on in the brain that leads them to overeat anyway.