Washington: Exposure to stress after a short and strict dieting regime increases the risk of binge eating and may lead to weight gain, a new study on mice has found.
Researchers at the University of Pennsylvania found that stressed-out mice with a history of such crash dieting ate more high-fat foods than similarly stressed mice who were not subjected to dieting.
The findings, published in The Journal of Neuroscience, suggested that moderate diets change how the brain responds to stress and may make crash dieters more susceptible to weight gain.
Crash diets, also called yo-yo diets, temporarily helps one lose weight quickly but is considered dangerous for the body. It involves drastically cutting back on the amount of calories and fat that one takes in on a daily basis.
For the study, the researchers examined the behaviour and hormone levels of mice put on crash diets. After three weeks, they were found to have lost 10 to 15 per cent of their body weight, similar to human diet weight loss.
While previous studies have showed that mice on lifelong calorie-restricted diets live as much as 50 per cent longer than their well-fed peers, little was known about the long-term consequences of quick-fix diets.
Lead researcher Tracy Bale and her colleagues found the mice on diets had increased levels of the stress hormone corticosterone and displayed depression-like behaviour.
They also discovered that several genes crucial for regulating stress and eating had changed.
Previous research has shown that experiences can alter the form and structure of DNA, an effect known as epigenetics.
Even after the mice were fed back to their normal weights, the epigenetic changes remained, found the researchers.
To investigate whether those molecular changes will affect future behaviour, the researchers put the mice in stressful situations and monitored how much fatty foods they ate. The previously restricted mice ate more high-fat food than normal mice.
"These results suggest that dieting not only increases stress, making successful dieting more difficult, but that it may actually `reprogramme` how the brain responds to future stress and emotional drives for food," Bale said.
The findings showed the underlying mechanisms for why a piece of pizza is so appealing after a stressful day at work, said the authors, suggesting that future weight loss drugs may target these stress-related molecules.
Jeffrey Zigman, an expert in endocrinology, diabetes, and metabolism at the University of Texas Southwestern Medical Centre, said the conditions the mice experienced mimic the type of psychosocial stress that people often experience.
"This study highlights the difficult road that human dieters often travel to attain and maintain their weight loss goals," Zigman said.
"It also suggests that management of stress during dieting may be key to achieving those goals."