08 Jul 2014

The incidence of obesity and related diseases such as Type 2 diabetes, particularly amongst youth populations, is rising at an alarming rate. But who or what is to blame for this modern epidemic? Neuroscientists believe that the answer lies deep within our subconscious mind and the brain processes that evolved to adapt to a much earlier period in our human history.

In the last part of the 20th century, dramatic developments in medical imaging technology provided neuroscientists with the ability to “see inside” the functioning human brain and gain a much greater understanding of how and why our brains behave the way they do. One of the most surprising discoveries was the extent to which our behaviour is driven by brain processes that operate below our conscious awareness. Embedded deep within our limbic system, these implicit emotional brain systems are now known to play a much greater role in controlling our motivations, shaping our desires and determining the choices we make, than we had ever thought possible. Yet all this goes on without our explicit realization, including in the context of the foods we buy and the lifestyle choices we make. But as we understand more about how these brain systems work and why they have evolved to operate the way they do, we will be able to devise much more effective dietary programs that can sidestep the pitfalls of our genetic programming.

Globalisation and industrial farming has meant access, not only to greater quantities of food, but also to a much wider variety. And while dietary guidelines now place considerable emphasis on portion-control, much less has been disseminated about the impact of variety on over-eating behaviours. The simple fact is that the speed of technological advances in food production and distribution has far-outstripped the pace of natural human evolution, making it very difficult indeed for us to adapt in time to such a rapidly changing environment. Only a few thousand years ago when access to food was unpredictable and subject to annual climate changes, our ancestors survived in periods of food scarcity because of brain mechanisms that had evolved to ensure our survival. The brain evolved to make us crave fatty foods and sugars, whose consumption and storage (in the body) in periods when such foods were abundant would help sustain the body during months of scarcity.

The brain also evolved a mechanism that neuroscientists refer to as “sensory-specific satiety” – a neural stop signal that controls over-consumption by making us feel sated after we have consumed the appropriate amount of one particular type of food. And while these mechanisms evolved when the quantity and variety of foods were modest, the current explosion in access to both factors has meant that our inherent food control mechanisms are no longer able to cope. The craving for fats and sugar which evolved to ensure our survival is now racing out of control, and the food-specific satiety signals between the brain and gut, overwhelmed in the face of so many different food choices, is ceasing to be an effective moderator of consumption.

So what, if anything, can we do about over-eating? If the mechanisms that control our behaviour are involuntary and habitual, and exert their influence subconsciously, are we helpless to respond? It turns out that, by understanding how these changes in our environment affect brain control mechanisms, we can now make small changes to our dietary and purchasing behaviour that will allow these automatic systems to function effectively again without the need for iron-strong willpower that so often fails to work. Below are a few practical applications arising from these insights in neuroscience that if implemented on an individual basis, can help leverage the natural in-built neural consumption controls that evolved to maintain a healthy weight and diet:

Small changes have a big impact
Many foods today are high in salts, sugars and fats – and given our inherent craving of these substances, how can we reduce our consumption of them and make alternative choices that nevertheless satisfy the cravings generated in our brain? One of the findings that have emerged from the field of cognitive psychology is that small changes often go unnoticed, experientially. And as sugar and other related substances typically stimulate the release of dopamine (the brains’ “feel-good” chemical), naturally, as with other addictions, giving up completely or “going cold turkey” takes a huge amount of willpower and is often doomed to failure as the foodie in your subconscious brain wrestles back control. But by systematically reducing the amount of sugar, salt and fat in your diet (tiny amounts on a daily basis), the chemical balances in the brain will likewise, systematically adapt to obtain reward from the lower levels – meaning you will experience just as much pleasure in time to small levels of sugar, salt and fat as you once did when you consumed much higher levels.

Fooling the brain
Many of us have heard of the old adage that “we eat with our eyes”, but research on how the senses combine information in the brain shows that what we see (such as the colour, shape, size and even the packaging of a food item) can dramatically alter how we actually perceive the way a food tastes. Sound and in-mouth-feel can also hijack the perceived flavour of foods, whereby louder high frequency sounds emitted during the bite of a crisp or the crackle of it’s packaging can make it seem super-fresh. Flavourless orange-coloured drinks can be perceived as “tasting orange”. We can also fool the brain into feeling sated by presenting it with large portions of low calorie foods such as bulky salads, or serving smaller portion sizes of other foods served on smaller plates – thus creating the visual illusion of a more substantial meal with higher perceived calories than is actually the case. By introducing other sensory experiences such as lots of differently coloured foods and crunchy alternative textures on the same plate, the experience of the meal can be both enhanced and prolonged, and without any loss of perceived pleasure that would otherwise have been derived from higher calorie options.

Variety is the spice (but also the vice) of life
Sensory-specific satiety helps the body to eat just what it needs, but no more, by limiting the palatability of a food once it has been consumed to the point of satiation. Hence, if you keep eating one banana after another, you will soon feel full and the desire to continue eating will cease. However, as if by magic, if you are immediately offered a different type of food, such as a juicy looking steak, the hunger pangs and desire to eat will return and you will start salivating to the new option. By limiting the amount of choices that we put in front of ourselves, we can learn to leverage this automated built-in neural mechanism and lose or maintain weight without feeling constantly hungry and deprived (at which point, we are back to the requirement for willpower). While variety is one of the true spices of life and should be celebrated, moderating the number of times a week where such variety is available can be a beneficial tool in the fight against obesity.

These are just a few of the ways in which neuroscience is helping with the fight against obesity. Understanding the rules by which our brains control (or fail to control) our eating behaviour can help us to devise interventions that can more successfully overcome the challenges associated with access to the plethora of delicious (but not necessarily healthy) food options that grace our supermarkets today. The more we uncover about our amazing brain, the more we can start regaining control over our environments and ultimately, over ourselves.

Further Information
Professor Gemma Calvert is an internationally renowned cognitive neuroscientist, Founder and Managing Director of neuro-marketing agency, Neurosense; member of the Global Agenda Council on Neuroscience and Behaviour for the World Economic Forum; fellow of the UK Centre for Science and Policy and member of the Scientific Advisory Board of the Neuromarketing Science and Business Association.


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