There are no doubts that the food we eat plays a significant role in our mood. On the other hand, what we eat and how much we eat can also be influenced by our current mood.

From a biochemical perspective, food is a complex mixture of chemicals that, once it enters the body, interacts with multiple physiological systems including the brain. It is well recognized that many people go for so-called “comfort foods” when they are stressed and need to improve mood. Chocolate, for example, profoundly affects mood by increasing positive feelings and relieving fatigue-like symptoms. This is due to the presence of psychoactive chemicals and amines in chocolate that greatly stimulates the brain and helps elevate mood. Another example is caffeine found in coffee and tea that precipitates anxiety in susceptible persons. Due to its stimulating effects, withdrawal can occur when caffeine intake is halted abruptly.

Pleasure has a great role to play in determining food choices. The relationship between food and mood is bi-directional: food affects the person’s mood through physiological mechanisms, and the person’s mood plays a strong role in determining the choice of food.

The craving for certain types of food, particularly sugar-rich food or food high in fat, can be brought about by stress, anxiety, or depression. Taking such foods can result in temporary mood improvement. The phenomenon is often observed in people who suffer from seasonal affective disorder, obesity, and severe pre-menstrual syndrome. The feeling of anger can accentuate comfort and impulsive eating. Joy, on the other hand, heightens the feelings of eating for pleasure. One way or another, changes in mood have the potential to cause binging on rather unhealthy foods.

Brain mechanisms: how food influences mood?

Brain cells communicate through chemical messengers called neurotransmitters. Serotonin is one of the most important neurotransmitters in the body and is found throughout the nervous system. It plays a significant role in mood, sleep, and appetite regulation. The release of serotonin in the brain is modulated by food intake, among other things.

Protein- and carbohydrate-rich diets greatly affect serotonin production in the brain. For example, a diet rich in protein decreases serotonin synthesis by limiting the availability of tryptophan, the chemical precursor of serotonin in the brain. Tryptophan, together with several other amino acids such as valine, leucine, methionine, phenylalanine, and tyrosine, belong to the group of large neutral amino acids (LNAAs). LNAAs share similar carrier proteins that enable them to pass through the blood-brain barrier. Usually, these LNAAs compete for the transport proteins. A diet rich in protein, therefore, increases the concentration of LNAAs in circulation. Furthermore, tryptophan is known to be one of the less common amino acids available in food protein, increasing competition for carrier proteins and eventually resulting in limited entry of tryptophan through the blood-brain barrier.

On the other hand, a carbohydrate-rich diet with a relatively limited intake of proteins indirectly facilitates the entry of tryptophan through the blood-brain barrier. As most amino acids are utilized by the muscle tissue, more carrier receptors become available to bind tryptophan. However, a diet too low in proteins reduces the availability of all amino acids, including tryptophan.

The relationship between mood disorders and eating disorders

Mood disorders and eating disorders share a bi-directional relationship. In fact, mood disorders are often diagnosed with an accompanying eating disorder as a comorbidity. Approximately 5% of women who suffer from the mood disorder major depressive disorder also have an eating disorder (e.g., anorexia nervosa, bulimia nervosa, or binge-eating disorder). Some evidence shows that these conditions share similar etiological factors, such as serotonin dysfunction.

Mood, food, and obesity

Obesity is often accompanied by mood disorders such as major depressive disorder and increases the incidence of other mood disorders such as anxiety disorders. Obesity that is brought about by overeating suggests an addiction similar to drugs due to a physiological dependence on food rich in fat and carbohydrates. As previously mentioned, palatable food may temporarily reduce the acute feeling of stress. However, chronic stress is often observed in obese individuals. Researchers found that mood disorders and obesity are both characterized by a deficiency in the dopamine pathway. When eating becomes an addiction, food intake works as a reward stimulus in some parts of the brain. It stimulates the dopaminergic neurons from the ventral tegmental area and substantia nigra. This activity promotes the cycle of overeating as a potent reliever of mood upsets in obese patients.

The hypothalamic-pituitary-adrenal axis (HPA axis) also plays role in the connection between food and mood. Chronic stressful experiences and changes in the dopaminergic and serotonergic pathways affect the HPA axis. Chronic stimulation of the HPA axis is linked to resistance to glucocorticoids, which is seen in up to 50% of patients with mood disorders. Stressful conditions stimulate the hypothalamus to release corticotropin-releasing hormone (CRH), which in turn elevates the level of adrenocorticotropic hormone (ACTH) released by the pituitary gland. This eventually causes the adrenal glands to secrete glucocorticoids. The exaggerated release of CRH in mice was shown to be linked with resistance to insulin, increased food consumption, weight gain, and the impaired ability to cope with stress.

Can mood modification influence body weight?

In some studies, a carbohydrate-rich/protein-poor diet supplemented with tryptophan was shown to facilitate mood modification. It is likely that mood improvements caused by such modifications of diet may reduce the frequency of comfort eating and thus results in a reduction of body weight, but this has not yet been demonstrated by proper research studies.

Self-monitoring is essential for the success of any weight loss program. Self-monitoring includes recording daily logs of diet, exercise, and self-weighing. There are still no scientific studies to confirm the effectiveness of incorporating moods into an individual’s daily self-monitoring regimen but anecdotal evidence supports the psychological advantage of recording mood and food daily.

The analysis of the bi-directional relationship between food choice and mood reveals a rather complicated system of signals and processes that can greatly influence a person’s quality of life and body weight. We still don’t fully understand how to use this knowledge to fight the obesity epidemic but it is likely that further research will reveal some new interesting approaches.

References

Hulsken, S., Märtin, A., Mohajeri, M. H., & Homberg, J. R. (2013). Food-derived serotonergic modulators: Effects on mood and cognition. Nutrition Research Reviews, 26(2), 223-34. doi: 10.1017/S0954422413000164

Lasikiewicz, N., Myrissa, K., Hoyland, A., & Lawton, C. (2014). Psychological benefits of weight loss following behavioural and/or dietary weight loss interventions. A systematic research review. Appetite, 72, 123-137. doi: 10.1016/j.appet.2013.09.017

Polivy, J., & Herman, C.P. (2005). Mental health and eating behaviours: A bi-directional relation. Canadian Journal of Public Health, 96, S43-6, S49-53. PMID: 16042164

Prasad, C. (1998) Food, mood and health: a neurobiologic outlook. Brazilian Journal of Medical and Biological Research, 31(12), 1517-1527. doi: 10.1590/S0100-879X1998001200002

Simon, G. E., Von Korff, M., Saunders, K., Miglioretti, D. L., Crane, P. K., Van Belle, G., et al. (2006). Association between obesity and psychiatric disorders in the US adult population. Arch. Gen. Psychiatry 63, 824–830. doi:doi: 10.1001/archpsyc.63.7.824

Singh, M. (2014) Mood, food, and obesity. Frontiers in Psychology 5, 925. doi:doi: 10.3389/fpsyg.2014.00925

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