Yo-yo dieting increases risk of comfort eating : LC Research/Media Forum : Active Low-Carber Forums

#1 ^

Wed, Dec-01-10, 04:39

Demi

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Yo-yo dieting increases risk of comfort eating

Quote:

From The Telegraph
London, UK
December 1, 2010

Yo-yo dieting increases risk of comfort eating as it changes how the body deals with stress

Yo-yo dieting can increase stress levels and make you more likely to reach for cake and biscuits after a hard day, new research has found.

The repeated loss and gaining of body weight – often at unhealthy rates – appears to reprogramme how the brain deals with stressful situations and cravings for food.

The effect is so profound that it changes the structure of DNA in areas known to release hormones designed to manage anxiety, the study discovered.

Researchers examined the behaviour and hormone levels of mice on limited diets and compared them with those on a normal diet.

After three weeks of fewer calories, the dieting mice lost 10 to 15 per cent of their body weight, similar to human diet weight loss.

But these rodents were also found to have increased levels of the stress hormone corticosterone and displayed depression-like behaviour.

The authors also discovered that several genes important in regulating stress and eating had changed.

Previous research shows 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.

To investigate whether those molecular changes might 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.

Dr Tracy Bale, who led the researchers at the University of Pennsylvania, said: "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."

The findings illustrate the underlying mechanisms for why fatty and sugary food is so appealing after a stressful day at work.

The authors suggest that future weight loss drugs may target these stress-related molecules.

Dr Jeffrey Zigman, an expert in endocrinology, diabetes, and metabolism at the University of Texas Southwestern Medical Center, 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," Dr Zigman said.

"It also suggests that management of stress during dieting may be key to achieving those goals."

The research was published in the Journal of Neuroscience.

http://www.telegraph.co.uk/health/h...ith-stress.html

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#2 ^

Wed, Dec-01-10, 07:55

teaser

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ScienceDaily also reported on this.

http://www.sciencedaily.com/release...01130171955.htm

I was hoping they'd have some more information, whether or not the mice were obese to start with, for instance. Mice are generally leaner than humans, maybe that would have an effect on the response to dieting down by ten or fifteen percent.

This article in the "relateds" is interesting;

Quote:

Changing To A Low-Fat Diet Can Induce Stress

Using a variety of standard measures of mouse behavior, researchers acclimated mice to either high-fat (HF) or high-carbohydrate (HC) diets, abruptly replaced those diets with standard chow, and observed behavioral changes. The brains of the mice were also examined for increases in corticotrophin releasing factor (CRF) levels which can indicate high stress levels.

Writing in the article, Tracy L. Bale, Ph.D., states, "Our behavioral, physiologic, biochemical, and molecular analyses support the hypothesis that preferred diets act as natural rewards and that withdrawal from such a diet can produce a heightened emotional state." Once deprived of their preferred diet, mice would overcome their natural aversion to bright environments to obtain the HF foods, even when standard food was available.

The abstract for this study;

Quote:

Decreases in Dietary Preference Produce Increased Emotionality and Risk for Dietary Relapse

Background
Obesity is a modern health epidemic, with the overconsumption of highly palatable, calorically dense foods as a likely contributor. Despite the known consequences of obesity, behavioral noncompliance remains high, supporting the powerful rewarding properties of such foods. We hypothesized that exposure to preferred diets would result in an amelioration of stress responsivity via activation of reward pathways that would be reversed during dietary withdrawal, increasing the risk for relapse and treatment failure.

Methods
Mice were exposed to preferred diets high in fat or carbohydrates for 4 weeks and then were withdrawn to house chow. Behavioral, physiologic, and biochemical assays were performed to examine changes in stress and reward pathways.

Results
These studies revealed significant changes in arousal and anxiety-like behaviors, limbic corticotropin-releasing factor expression, and expression of reward-related signaling molecules in response to the highly preferred high-fat diet that was reversed by withdrawal. In a dietary-reinstatement model, mice withdrawn from the high-fat diet endured an aversive environment to gain access to the preferred food.

Conclusions
Exposure to a highly preferred diet high in fat reduces stress sensitivity, whereas acute withdrawal from such a diet elevates the stress state and reduces reward, contributing to the drive for dietary relapse.

At least two ways to look at this. (If this applies to humans, and not just mice.) Stress increases preference for fat, according to the Telegraph story. So stress makes fat make us fat. Or, fat is soothing, and at some increased level of fat intake as a percentage of diet, appetite might actually be reduced. The fat doesn't make us fat, we just have an increased appetite for fat that isn't satisfied by protein or carbohydrate.