Technological change is so rapid that we can’t keep up. Our brains have evolved over millions of years to cope with our environment, from our flight or fight response, to hunter-gathering, and the invention of agriculture. However, we never stop to consider how our ancient brains manage in our modern world.

Our bodies were built for survival. But they were built to survive in the Stone Age. It takes around 200,000 years for a beneficial mutation to spread throughout the human gene pool. That means we should have begun developing changes to manage in our modern world about 200,000 years ago. Needless to say our ancient brains have not evolved at a rate to match all our technological advancements. But why does that lead to stress, and how can it affect our health?


We are hard-wired to interpret our environment, and detect any threats in order to help ensure our own survival. We always react to perceived threats in the same way – the fight, flight or freeze response.

However, we can’t distinguish between different types of threat, a lion is the same as a morning alarm or being fired from work. This means we also tend to interpret any stress as a threat, and as a result we often find ourselves in a constant state of stress.

For example, imagine a glass of water represents your capacity for stress. Your day begins with a stressor – your alarm goes off in the morning, and it pours water into your glass. You hit the snooze, and there’s another stressor, now you’re running late. You skip breakfast – another stressor. And traffic is backed up – another stressor. You arrive late for work – stressed. And your manager calls you into the office – your glass is almost full. There is a problem at work you need to sort. By the time you get to your desk – your glass overflows. All before 9.30 a.m.

Most of what we interpret as threats to our survival are minor stresses that quickly build up, flooding our body with “survival energy.” But what is all this stress doing to our bodies? And how do we prevent our ancient brains from becoming overwhelmed?


Stress causes “diseases of civilization,” including high blood pressure, strokes, heart attacks, diabetes, irritable bowel syndrome, neck and lower back pain, and cancer.

Just like our bodies interpret any stress as a threat, all those stresses are happening all of the time. Your body can’t distinguish between past, present or future. So remembering yesterday’s threat, trying to face one today, or thinking of the troubles tomorrow are all interpreted as happening now and our bodies respond accordingly.

Stress has become ubiquitous with modern life – producing feelings of overwhelm, tension and worry – all of these are directly effecting not just our ancient brains but our metabolisms as well. The release of stress hormones such as cortisol and adrenaline trigger bodily responses in accordance with our flight or fight response. Increased heart rate redirects blood flow towards our limbs and away from our digestive and immune systems, to better enable us to battle or flee from predators.

That’s convenient for when a lion jumps out at us when we come out of Costa!

However – our short-term stress responses aren’t so well suited to modern life. Especially if our day is filled with a whole pride of lions just waiting to surprise us!

Our stress response being active for longer periods means the short bursts of adrenaline that would give us motivation and energy to face challenges, become a steady stream that leads to us feeling run down. This is known as allostatic load – the “wear and tear on the body” caused by chronic stress.

allostatic load

The prolonged release of stress hormones can put us at greater risk of cardiovascular diseases and obesity, while weakening our immune systems, damaging our digestive systems, and even reducing our ability for learning and memory, as our attention is constantly directly to perceived threats. An overflow of stress hormones can even lead to increases the permeability of the gut lining, meaning bacteria can pass through the gut into the blood stream, in turn triggering immune system responses, causing over-sensitivity or allergies to certain foods. It can also lead to changes in the composition of the gut microbiome – all this means our bodies aren’t functioning optimally, and we are far more likely to develop resulting health problems as we struggle through each stress-filled day.


But can stress really make you fat? What does Cortisol really do?

Hormones are the delivery-men of the body; they send signals back and forth between the body and the brain, in response to our internal and external environment.

Cortisol is released in the body during times of stress along with the hormones epinephrine and norepinephrine, these constitute the “fight or flight” response to a perceived threat. Following the stressful or threatening event, (the Costa lion, or Jackie from accounts trying to talk to us at lunch) epinephrine and norepinephrine levels return to normal, while cortisol levels can remain elevated over a longer time period. And can remain persistently elevated in the body when a person is subjected to chronic stress.


One ultimate goal of cortisol secretion is the provision of energy. Cortisol stimulates fat and carbohydrate metabolism for fast energy, in addition to stimulating insulin release and maintenance of blood sugar levels. The end result of these actions is an increase in appetite. Therefore, chronic stress, or poorly managed stress, may lead to elevated cortisol levels that stimulate your appetite, with the end result being weight gain or difficulty losing unwanted pounds.

Cortisol not only promotes weight gain, but it can also affect where you put on the weight. Researchers have shown that stress and elevated cortisol tend to cause fat deposition in the abdominal area rather than in the hips. This fat deposition has been referred to as “toxic fat,” since abdominal fat is strongly correlated with the development of cardiovascular disease.

The way stress levels affect an individual’s cortisol levels is less easy to predict, since the amount of cortisol secreted can vary – with some being innately more reactive and others less reactive to perceived “threats” (Maybe you aren’t afraid of lions or Jackie from accounts!).

However, when we feel more stressed, our bodies are going to respond with more force to protect us – that can mean increased appetite and increased cravings. This can easily lead to over-eating or eating  to relieve our feelings of stress.

Our environment then, can be another contributing factor to weight gain. And stress management can be vital when it comes to trying to lose weight, maintain a healthy lifestyle, and prevent disease. We need to find ways to manage the stress on our bodies and our ancient brains – through adopting stress-relieving activities such as meditation, hobbies, or good old fashioned exercise.

Exercise has been shown to be one of the best ways to combat stress, due to the release of endorphins, which have natural stress-fighting properties and can help lower cortisol levels. So when we are struggling with diet regimes or weight gain – we also need to consider other factors, like stress and how it is impacting our bodies. We always need to pay attention to our environment, and the changes we can make to our lifestyle in order to help our ancient brains manage in our modern world in order to lead healthier, happier and less-stressed lives.


For further advice on nutrition and training, check out the links below to find a program that suits you and your lifestyle – whether you want a new personalised training plan, personalised nutrition, or private training sessions – we have something to support your goals.