Learn to control the reward centres of your brain
Stress is bad for your mental health. It’s not great for your heart or immune health, either. Furthermore — and just to rub salt into your wounds — it can also make you fat. But the consequences of stress are not inevitable: once you understand what’s going on, you can fight back.
Stress can also be good for your mental health and overall survival. The stress response is designed to save your life, when called upon to do so. It also stimulates imagination and creativity. Likewise, eating is both essential and a pleasure. Issues arise when normal stress crosses a line, and so too does normall eating.
At the heart of the turmoil created by mental anguish and overeating is the brain’s reward system and the hormones that interact with it, in particular ghrelin.
Ghrelin is the hunger hormone, produced mainly in the stomach. When all is working well, it tells your brain when you are hungry. Thus, starvation is avoided. But with prolonged, unrelenting stress the normal ghrelin response is disrupted and you fail to differentiate between genuine hunger and a craving for something to stop the stress.
The reward system directs us away from pain and towards pleasure. We’d all rather stay and have another drink than go home and face the music. Pleasure takes the form of not only food but also addictive substances, including drugs and alcohol.
Several areas of the brain form part of the reward system, and they are activated by the neurotransmitter dopamine.
There are two major dopamine pathways involved in the reward system, the most important being the mesolimbic dopamine pathway. This connects a region of the brain called the ventral tegmental area (VTA) with a region called the nucleus accumbens (NAcc), found in the ventral striatum.
The VTA is the main source of dopamine, produced in anticipation or expectation of a reward. This dopamine ‘projects’ to the nucleus accumbens, the reward centre. When this happens, you experience a surge in the feeling of pleasure.
Dopamine also projects to the hypothalamus, the hippocampus, the amygdala, and the prefrontal cortex. These regions are concerned with memory of a particular reward, the emotional associations you make with that reward and the choices you subsequently make. Therefore, the effect that dopamine has in these regions is to remind you of how much you like something, how good it makes you feel and why you should have it again.
We form a memory of something pleasurable and produce dopamine when that something becomes available again. When it comes to addictive substances, more and more dopamine is produced, meaning ever more amounts are required to get the same high.
Food is a source of reward and pleasure, and this is where ghrelin comes into the equation. Circulating ghrelin levels are elevated following stress. This excessive ghrelin is able to override any feeling of fullness you may have by directly targeting the VTA and nucleus accumbens, and increasing levels of dopamine, “to increase food motivation”.
“Ghrelin has recently emerged as one of the major contributing factors to reward-driven feeding that can override the state of satiation”
Ghrelin promotes food intake, even when satiety has been achieved. You are unaware that you are full and go seeking a reward. Not surprisingly, overweight people have been observed to eat more when stressed, in the absence of hunger.
The reward you seek doesn’t take the form of anything too healthy, obviously. No — what you want is what is euphemistically termed “palatable” foods, and which you may know as comfort foods. These are foods that combine fat with sugar.
Palatable, processed and guaranteed to provide
Now, there’s nothing at all wrong with fat — readers of this publication will be aware of just how vital the right kind of fat is to the human body, in particular the brain. Fat on its own does not provide reward; you’re unlikely to crave a lump of butter when you’re going through hell. But think about something that combines fat with sugar — think chocolate — and your reward centres light up like a Christmas tree. The list of palatable foods is a long one: cake, cookies and all things sweet, plus crisps, chips and every form of refined carbohydrate snack (which are essentially sugars), combined with vegetable oil to provide the fat component.
Just about every form of processed junk food available to you is designed by manufacturers to feature this winning combo, guaranteed to provide the dopamine you crave, and then some. They know precisely what they are doing.
“..the power of the reward system over feeding behaviour should not be underestimated.”
Palatable foods offset normal appetite control. Injection of ghrelin into the VTA of rodents has been shown to increase the intake of palatable food. Rats, like humans, have a predilection for anything that combines fat and sugar to create a powerful reward. The association between stimulus and reward is quickly established.
Newton’s Third Law of Motion states that everything has an equal and opposite action. In the case of ghrelin, that opposite is the hormone leptin.
Leptin signals satiety to the brain. It is a ghrelin antagonist that regulates and reins in the reward system. Ghrelin antagonists suppress the intake of palatable food by suppressing the mesolimbic dopamine pathway and the desire for reward foods.
In the same way that injection of ghrelin into the brains of rodents stimulates intake of fatty, sugary foods, direct injection of leptin into the VTA reduces food intake and suppresses the desire for those foods.
Leptin has this effect on humans, too. One week of leptin treatment for obese individuals who are leptin-deficient can alter the reward system response to visual food cues.
“There is considerable evidence that the mesoaccumbal dopamine system appears to be a key target for leptin.”
Leptin is key to appetite control. Secreted predominantly by fat cells, and in the small intestine, leptin informs the brain that you are full, and further eating is not required.
But before attempting to lower ghrelin and increase leptin, there’s another hormone that should be taken into consideration: cortisol. Cortisol is the main stress hormone.
The stress response and the HPA axis
The body comes hardwired to deal with stress. Stress management is part of our evolutionary make-up. If it wasn’t, we wouldn’t have survived this long. The stress response is a sublime example of biological engineering designed to ensure you survive the stressor; tis pity you are too overwrought to appreciate its beauty when it swings into action.
When stress happens, your body moves to protect you by activating the hypothalamic-pituitary-adrenal (HPA) axis. This axis is the line of communication between the hypothalamus in the brain and the two adrenal glands that sit on top of the kidneys.
When the HPA axis is activated, the hypothalamus signals to the pituitary gland to secrete adrenocorticotropic hormone (ACTH). ACTH leaves the brain and travels in the blood to your adrenal glands.
Once there, ACTH triggers the secretion of glucocorticoid hormones, including cortisol. In the right amount, cortisol is beneficial. Among other things, this hormone increases your mental and physical energy, is anti-inflammatory, and improves your mood.
Dysfunction arises when stress is prolonged, and too much cortisol is produced. Normally, this hormone is produced cyclically in what is termed the circadian rhythm: levels start to rise between 3am and 6am and gradually decrease throughout the day so that by night-time they are at their lowest. Too much cortisol, at the wrong time, and you may experience headaches, insomnia, poor immunity, and weight gain, especially around the abdominal area.
Activation of the HPA axis triggers cortisol release and stimulates the dopamine reward system, increasing craving for highly palatable foods.
“The stressed brain expresses both a strong drive to eat and an impaired capacity to inhibit eating — together creating a potent formula for obesity.”
Your three-step programme for better appetite control
Stress increases both ghrelin and cortisol, and elevated levels of these two hormones disrupts the brain’s reward systems, suppressing satiety and increasing the desire for palatable food. Here are three ways you can exert control over those hormones.
- Programme your body deal with stress in order to lower cortisol. You’d be surprised at just how well your body can cope, given the right nutritional terrain. This includes balancing blood sugar, eating the right kind of fat (and protein) and providing the adrenals with the nutrients required for optimal functioning. There isn’t space here to go into all the details of what that entails, but you can find out more from my article “How to Manage Your Stress by Changing Your Diet”.
- Control ghrelin and optimise leptin, your ghrelin antagonist. Again, diet is key to achieving this. For details of how to do this, see my recent article, Three Effective Ways to Control Your Hunger Hormones.Confront the stress in your life. That’s the tricky one. There is no one unique solution; the best approach combines stress management, relaxation techniques and of course dietary manipulation. Stress is one area where a truly holistic approach is crucial if you are to get effective results.Confront the stress in your life. That’s the tricky one. There is no one unique solution; the best approach combines stress management, relaxation techniques and of course dietary manipulation. Stress is one area where a truly holistic approach is crucial if you are to get effective results.
- There are techniques you can adopt yourself and techniques which require the help of others. Exercise is a good starting point because this is something you can initiate on your own. Exercise is important because it helps normalise levels of stress hormones in the blood, and improves circulation. It also stimulates the release of endorphins — ‘happy hormones’ — that can elicit a sense of wellbeing and positivity. Aerobic exercise stimulates the production of cortisol, so ideally should be carried out in the morning only. Cortisol naturally falls towards evening, in preparation for sleep.
In addition to exercise, there are other effective tools you can utilise to manage stress levels. Your method of choice is a matter of what you feel drawn towards. Possibilities include meditation, positive imagery and deep breathing techniques. If you feel you need a talking therapy, you might want to consider some professional help from a stress clinic counsellor.
Stress can take the form of an event, or even just a thought. Your body doesn’t distinguish. You can trigger the same stress response just by remembering something, or being reminded of something, that happened years ago.
You can’t avoid stress, but you can fortify your defences and change your diet to change your hormonal response.
Stress highlights the link between diet and mental health, and how food influences brain function. How what you eat can change the way you feel, sharpen your focus, and affect your memory.
Copyright © 2020 Maria Cross All rights reserved.