Stress-induced obesity and the emotional nervous system

Abstract

Stress and emotional brain networks foster eating behaviors that can lead to obesity. The neural networks underlying the complex interactions among stressors, body, brain and food intake are now better understood. Stressors, by activating a neural stress-response network, bias cognition toward increased emotional activity and degraded executive function. This causes formed habits to be used rather than a cognitive appraisal of responses. Stress also induces secretion of glucocorticoids, which increases motivation for food, and insulin, which promotes food intake and obesity. Pleasurable feeding then reduces activity in the stress-response network, reinforcing the feeding habit. These effects of stressors emphasize the importance of teaching mental reappraisal techniques to restore responses from habitual to thoughtful, thus battling stress-induced obesity.

Figure 1

During stressful period, there is a change in what kind of food is eaten, independent of hyperphagia or hypophagia. There is a shift in food intake toward ‘comfort foods’ that is independent of whether total caloric intake increases (dashed line) or decreases (solid line) from normal intake (horizontal dot-dashed line). Student intake was retrospectively interrogated during periods of no stress (normal) or exam stress; the type of foods eaten and the amounts of foods were compared during the two periods. Whether or not food intake increased or decreased, the kind of food ingested shifted toward the more palatable sorts (from [14], with permission).

Figure 2

Brain structures engaged in feeding behaviors. (a) At the cortical level, the emotional brain is embedded in the anterior insula that provides ‘feelings’ and in the anterior cingulate cortex that governs ‘motivated behavior‘. (b) The limbic brain is responsible for emotional (amygdala), motivational (nucleus accumbens), and habitual (basal ganglia) responses, while (c) the brainstem, containing the hypothalamus, brainstem and spinal cord, regulates energy balance. Afferent inputs to the brain and to emotional and cortical structures are shown on the left, and efferent outputs from cortical and sub-cortical habitual and emotional structures are shown on the right. Horizontal interactions between afferent and efferent components exist at each level, and structures are also bidirectionally connected vertically. While the hypothalamic neurons are sufficient to regulate energy intake, components in the limbic brain and frontal cortex can override the basic maintenance of energy balance and result in either an underweight or overweight phenotype. The cell groups shown in yellow represent the brainstem and spinal cord portion of the brain that is engaged with the homeostatic maintenance of energy balance. The cell groups shown in orange can cause either an increase or decrease in food intake. DA, drug addiction.