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by author Alan C. Logan, ND, FRSH
The relationship between food and mood is mediated by both psychological and physiological factors. In the psychological realm, humans learn through reinforcement to expect palatable foods to positively influence mood states. Our emotional state can also influence the type and quantity of foods we consume. In the physiological realm, the nutrients and food-based chemicals we consume can influence both the structure and function of our nerve cells (neurons) and the communicating chemicals (neurotransmitters) that make them work. Psychological Aspects of Mood and Food Based on feelings of pleasure and satiation, eating becomes an activity which not only supplies essential nutrients for our survival but also becomes psychologically reinforced. Consumption of highly palatable foods–fats and sugar in particular–becomes readily associated with a positive influence, albeit temporary, on mood states. Through experience, eating foods we enjoy and find particularly tasty becomes associated with an expectation of mood elevation. The same is true of any pursuit of pleasure; with positive experience and the relief of discomfort there is repeated behaviour. High-calorie fat and sugar-laden foods are associated with rewards throughout life. Birthday cake, holiday treats, candy, and sweets are associated with important occasions and rewards in childhood. This follows into adulthood so that the full-fat venti latte with extra syrup and whipped cream becomes the reward for a stressful day: birthday cake in a cup. Stress-Related Eating Given that highly palatable foods can influence mood states, it should be no surprise that both acute and chronic stress can influence the quantity and types of foods we choose. Research shows that snacking on high-fat and high-sugar foods as a way of coping increases during times of stress. The first well-designed study, in Psychosomatic Medicine (1990), showed that in periods before major work deadlines employees make significant dietary changes. Intake of total calories, total fat, and overall percentage of calories from fat were significantly higher in the days leading up to work deadlines. Further research in the British Journal of Health Psychology (1998) showed that daily stress increases the consumption of so-called comfort foods–in this case, fast foods and sweets. In teenagers, the periods before exams lead to higher intakes of total calories, and those reporting greater stress had higher overall fat intake and less consumption of fruits and vegetables. In structured weight-loss programs, those reporting the highest levels of stress and depression at baseline are most likely to regain weight when followed for 18 months. In a study in Preventive Medicine (2002) involving over 5,000 adults, researchers showed that stress-driven eaters have a higher body mass index and report a preference for foods rich in fat and sugar. Depression and Obesity A higher level of depressive symptoms would be expected in obese patients due to social pressure, body image, and discrimination. However, research indicates that depressive symptoms can pre-date many cases of obesity; and in fact, a number of those who are overweight may be turning to food in an inappropriate effort to medicate depressive symptoms. In a group of almost 10,000 children, depression among seven- to 12-year-olds doubled the risk for developing obesity when assessed later. Separate researchers found a similar relationship between depression in childhood and adult obesity risk when children aged six to 17 were followed for 10 to 15 years. Sleep Deprivation Associated with both stress and depressive symptoms, sleep deprivation is linked to greater body fat in children and adults. In experimental studies, sleep deprivation alters appetite and increases food consumption by an incredible 250 percent. Physiological Processes of Food and Mood Modern science has shed significant light on the relationship between mood and food, which has been far from completely understood. Cortisol A common thread between chronic stress, sleep deprivation, and depression is an elevation in cortisol levels. This stress hormone increases the activity of the enzyme responsible for laying down abdominal fat and promotes fat storage and is also associated with increased body mass index and waist circumference.
Alan C. Logan, NS, FRSH, is a faculty member at Harvard Medical School’s Mind-Body Medical Institute and author of The Brain Diet (Cumberland House, 2006). Source: alive #288, October 2006 |
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