It has long been theorized that an association exists between long-term stress and obesity. Chronic stress can lead to “comfort eating,” which often involves the overeating of foods that are high in fat, sugar and calories, which, in turn, can lead to weight gain.

While short-term stress can cause a person to lose their appetite, chronic stress can have the opposite effect.

Stress in the short term causes the brain to produce an appetite-suppressing hormone called corticotrophin-releasing hormone. Signals are also sent to the adrenal glands that trigger their production of adrenalin, which temporarily suppresses any urge to eat as part of the fight-or-flight response. Ongoing stress, on the other hand, causes the release of a hormone called cortisol. This hormone increases a person’s appetite and if the stress does not pass, cortisol and appetite levels remain increased.

One study by University College London (UCL) researchers looked at whether there was an association between levels of cortisol present in the hair and BMI and waist circumference. Data was recorded over four years, for more than 2,500 men and women. The 2-cm pieces of hair analysed represented about 2 months’ worth of growth and the cortisol levels that had built up over that time.

Study leader Sarah Jackson and team found that higher levels of cortisol in the hair were associated with greater waist circumferences and higher BMIs. People who had a BMI of 30 or more and therefore classified as obese had especially high hair cortisol levels. Furthermore, retrospective analysis over the 4-year period showed a positive association between hair cortisol levels and the persistence of obesity over time.

In a British study, researchers found that people who had high cortisol levels in response to stress had a greater tendency to eat snacks when experiencing day-to-day problems than people who had a low cortisol level in response to stress.

Many animal studies have also suggested that stress influences food preferences, with foods rich in fat and sugar being preferred when subjects become either physically or emotionally stressed. These foods appear to inhibit brain activity that is involved in the processing of stress and anxiety, which has the effect of counteracting these emotions. Aside from overeating, stress can also lead to sleep problems, decreased motivation to exercise and increased alcohol consumption, all factors that increase the likelihood of weight gain.In another study from the Hebrew University of Jerusalem, researchers looked at the molecular mechanisms that may link anxiety and metabolism. Specifically, they looked at the link between the expression of a certain type of microRNA (mRNA) and processes related to metabolic syndrome. Hermona Soreq and team had already performed studies showing increased expression of microRNA inflammation regulators within the brain and gut in response to stress and anxiety, but the researchers wanted to explore any influence this had on obesity. They  found that mRNA expressed as a result of anxiety could increase the effects of processes related to metabolic syndrome. They also found that the mRNA expression level varied between different cells and tissues, depending on whether subjects had been exposed to stress.

Counteracting Stress

The main step a person can take if they find stress has increased their hunger levels and therefore waistline, is to eliminate foods in the diet that are high in fat and sugar. Some other recommendations are described below:

Exercise: When a person exercises vigorously, the cortisol level rises, although only in the short term. Gentle exercise, on the other hand, tends to lower cortisol.

Meditation: Many studies have demonstrated that meditation can decrease stress. It may also motivate people to be more alert about which foods they choose to buy.

Support: Being supported by friends and family seems to be beneficial in counteracting stress and research has shown that individuals working in typically stressful environments such as A&E departments are significantly less likely to have mental health problems if they feel supported by those around them.