Stress and food intake RESEARCH
Some people eat less and others more than normal in response to stress.
Â Innovative ways of tackling stress-related eating behaviour may help peopleÂ control weight and reduce underlying stress.Acute versus chronic stress When we perceive an immediate threat (acute stress), the brain sends a signal to a number of systems including the hypothalamic-pituitary-adrenal (HPA) system, and activates stress hormones. This activation triggers a cascade of events to prepare the body for action. For example glucose is mobilised to fuel the muscles and brain, the senses are heightened, theÂ heart works faster, and breathing quickens. This is commonly known as the "fight or flight" response, it evolved as a survival mechanism - enabling usÂ to react quickly to life-threatening events.
In a healthy stress response, levels of stress hormones such as adrenalin and cortisol rise to meet the demands of the situation and then fall rapidly once it is dealt with. In chronic stress there is a prolonged exposure to stress hormones, particularly cortisol, and the body may not return to homeostasis (a healthy resting state). This can have serious health consequences and adversely affect the immune, cardiovascular and central nervous systems.
Stress and eating behaviour
In acute high-level stress, such as under a serious physical threat, the appetite is suppressed.1 However, less intense but more long-term stress, like work pressure, can affect eating behaviour in different ways. It is estimated that around 30% eat less than normal when stressed, while most individuals eat more.2 The HPA stress response system, which shares the same neural pathways as the control of food intake, is thought to be central to explaining both under- and over-eating.
2 Individual responses
In response to stress, rats given standard chow eat less and lose weight. However rats eat more when exposed to palatable foods rather than standard chow, which suggests that pleasurable foods could help alleviate the
symptoms of stress.
Humans are regularly exposed to pleasurable foods. Some people use food as a way to relieve stress and counter negative emotional states, whilst others
do not. In people who strictly control their food intake (restrained eater
or dieter), stress can override their conscious control, leading to overeating of 'restricted foods'.1 There are also differences in people's ability to differentiate between hunger and other unpleasant internal states
like stress.3 It is suggested that perhaps those who are more 'tuned in' to their appetite and metabolism are the ones who eat less in response to stress.
3 Stress and body shape
Healthy men and women who exhibit increased cortisol reactivity in response to stress (in laboratory studies) have greater abdominal obesity, as do individuals with higher morning cortisol levels (a symptom of job and life
stress), compared to controls.2 Low socioeconomic status and job pressures, two indicators of chronic stress, have been associated with greater levels of abdominal obesity.4 It is suggested that chronically high cortisol levels
in synergy with high levels of insulin (a hormone that helps the body use glucose) encourages fat deposition around the waist.2 However not all studies find a link between stress and overall obesity levels.
5 A mindful approach Mindfulness programmes for stress reduction have been around for some time, and more recently have been applied to control disordered eating. They use
techniques which interrupt habitual thought patterns, emotions and behaviours, and enhance awareness of thoughts, feelings, and sensory experiences.3 This approach helps people get in touch with their internal signals (recognising hunger and fullness, emotions and external cues), rather than relying on learned responses. A recent literature review of mindfulness programmes found that 86% of studies reported improvements in targeted eating behaviours.6 This approach may not only improve food choices and help control weight, but reduce underlying stress as well.
Lutein, zeaxanthin may enhance visual performance A study published in Investigative Ophthalmology & Visual Science shows that lutein and zeaxanthin-compounds contained naturally in green, leafy vegetables, such as kale and spinach-supplementation may improve the ability for young, healthy people to see under glare conditions. The randomized, double-blind and placebo-controlled study took place at the University of Georgia in Athens over the course of 12 months.
In the study, approximately 100 young and healthy subjects were assessed and received daily dosage levels of 10 mg of FloraGLO lutein and 2 mg of Optisharp zeaxanthin, or a placebo over a one-year supplementation period. Macular pigment optical density (MPOD) and serum levels of lutein and zeaxanthin increased significantly in the supplemented group, while no changes were noted in the placebo group. The macula is the yellow spot in le for detailed central vision and the yellow color is the result of high concentrations of lutein and zeaxanthin.
Macular pigment optical density is a measure of the amount of macular pigment present in the macula and has been shown to have a major impact on visual performance.
The study looked at three aspects of visual performance: glare disability, photostress recovery time, and contrast enhancement. Glare disability is the amount of glaring light that can be tolerated by a person before vision is
severely impaired. Photostress recovery time determines how fast the eye can recover sight after experiencing a flash of bright light, while contrast enhancement is the ability to detect chromatic borders that allow discrimination of an object from its colored surroundings. The results of
the study demonstrate significant improvement in these aspects of visual performance and add to the growing body of evidence to support the role of lutein and zeaxanthin in helping to achieve optimal visual performance and comfort.
"Showing lutein and zeaxanthin improve function in normal healthy individuals widens its applications, as we continue to investigate the potential of nutrition to support both eye health and visual performance," said Billy Hammond Jr., the principal investigator of the study, University
of Georgia in Athens.
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