A new study exploring the relationship between stress and nighttime eating reveals that daytime stress helps fuel a double hormone whammy that predisposes us to the midnight binge.
We all function along hormonal seesaws influencing nearly every part of our lives. In the case of eating, certain hormones induce hunger, others fullness. Unfortunately for us, the evidence points toward hunger hormone levels increasing at night, and fullness hormone levels decreasing, which opens the door to overeating. And stress pushes us through it.
“Our findings suggest that evening is a high-risk time for overeating, especially if you’re stressed and already prone to binge eating,” says Susan Carnell, Ph.D., assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, and the study’s first author.
Study participants were 18-50 years old, all overweight, but otherwise healthy, and about half had been previously treated for an overeating disorder. They were evaluated in the morning and evening after fasting for eight hours and then drinking a 600-calorie liquid meal to stimulate fullness. A couple of hours later, they were given a standard stress test (placing one hand in a bucket of ice cold water for two minutes), and 30 minutes after that they were offered a pizza buffet complete with sides of chips, cookies and chocolate. Their blood was tested to measure stress and hunger hormone levels, and they were asked to rate how full or hungry they felt.
The results showed that time of day significantly influenced hunger levels – the participants’ self-reported appetites for the pizza and snacks were higher in the evening. And blood tests revealed lower levels of peptide YY, a hormone linked to reduced appetite, also later in the day.
All of the participants experienced more stress and hunger after the stress test, both in the morning and evening, but blood levels of a hunger hormone called ghrelin were higher at night. Previous research has shown ghrelin to be especially sensitive to daytime stress, and the latest study backs that up.