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  • Writer's pictureDr Susan Baxter


Updated: Mar 3, 2023

It’s no longer January; most of us have now abandoned their new year’s resolution to “Get fit and healthy”. Despite the most zealous of intentions, it is no secret that the majority of diets fail. In a poll by the UK newspaper the daily mail, the average diet lasts 5.5 weeks, with the average duration of a post-Christmas diet being even shorter at just three weeks.

This article investigates the physiological and psychological factors which are reducing your ability to reach your goals. Understanding why diets so often have an expiry date can help with how you might change your diet expectations for the better.  Also find out how you might harness the power of your psyche to make your diet a success.

One of the main reasons why diets are said to be doomed, is because of the modern-day shift in reward contingencies. Reward is a method through which behaviour can be shaped and reinforced. Often an unhealthy shift that people have made nowadays is to use food as a reward: you might remember being bribed as a child with a treat if you were ‘good’.

The same reward can be more ‘rewarding’ if it is delivered closer to the time that the desirable behaviour is performed. The behaviour becomes more reinforced as your brain associates the reward with the behaviour. If one considers that, through a mere click of a few smart screen keypad buttons, we can do anything immediately. We can order a dress or get weather updates from our smart phones NOW. In fact, we want, and indeed, expect to get everything NOW.

Apply this logic to junk food, which we often treat ourselves with. Sugar absorption in these high calorific treats is extremely fast. This means that the reward to the brain is delivered in extremely close proximity to the actual eating of the food. Dopamine circuits (the pleasure centre of the brain) are activated, and the behaviour of eating junk food becomes more satisfying over time.

The Science of Junk food:

According to a published article by Nature Neuroscience, high calorie food can be just as addictive as drugs. Just like drug addicts, the reward pathways were found to be blunted in response to sensitivity for the neural response pathways, which are usually activated during pleasurable experiences. This implicates a detrimental outlook for those activities which usually stimulate pleasure in the brain, such as exercise. These consequences make sense when you consider how hard it is to adapt to a new diet and healthy lifestyle. Just like drugs, there can be physiological withdrawal effects from reducing junk food, including headaches and moodiness. The positive effects to changing one’s eating and exercise habits are not immediately evident. This directly goes against our modern-day expectations of instantaneous reward in return for effort.

A problem with the instant reward system is that delayed rewards are perceived as less rewarding: which poses a problem for weight loss. Despite maximal efforts and best intentions, dieting (done in sustainable manner) will yield small progress towards a goal over the space of weeks and months. Furthermore, the small increments towards the underlying goal are not quite as satisfying when the perceived level of effort towards healthy food and exercise is high. This is a phenomenon known as “cognitive dissonance”. Expectations do not meet reality and usually the mind compensates by altering expectations and lowering the weight of the goal. The overall effect means that the tangible goal of losing, say 5kgs for example, becomes less important, and therefore the extra effort becomes exorbitant.

Conversely, a delay in punishment , or a negative reward, also does not do much to deter habitual behaviour as an instant punishment's would: which is why we can find ourselves needing a diet in the first place. Weight gain usually occurs slowly over time, and is often only identified once poor eating habits have already been formed. In short, the consequences of your Cheetos are not instantly visible on your hips and butt.

Therefore attempting a new regime which replaces your habits (of instant sugar reward) can quickly run out of steam: there are no visible and instant rewards for swapping your mint slice at lunch time for a salad. In fact, the apparent feelings of hunger or deprivation are perceived in the brain as pain, and stimulate the punishment receptors. These mechanisms are usually ones that are activated as a coping mechanism for survival and perception of pain, promoting the body to enhance avoidance, and release cortisol (the stress hormone).

The presence of the stress hormone cortisol is negative to your dieting intentions for a number of reasons, but some of the main ones which can de-rail your diet include sleep disruption, muscle catabolism, and reduced immunity, and in some cases emotional eating! From these, sleep disruption can be the most destructive: not only will you find yourself moodier, and making poorer decisions (for example when it comes to food and exercise), but ghrelin (the hunger hormone) becomes released, which can cause you to overeat to an extent of up to 500 excess calories a day!

The final stage in the dieting de-railing process is advancement in the prefrontal cortex. It is the prefrontal cortex that has been hailed as the responsible factor in making humans the top of the food chain. The prefrontal cortex can synthesis and make ‘real’ imagined thoughts and scenarios. Furthermore it has been advocated as part of the ‘placebo effect’. For instance, if you believe benefit or detriment can be derived by doing something, it will. It is this particular element which is the final ‘blow’ to your diet. Once the ‘slow’ progress results have been hailed as non-existent, the prefrontal cortex is secretly sabotaging any more progress being made. You think ‘nothing’s happening’ – and in thinking that, makes it true.

The goal of a new diet, therefore, becomes too cognitively difficult: this is understandable. Usually by the end of two weeks sleep disruption has affected our judgement; stress levels are high (with everyday problems escalating due to cortisol and junk food withdrawal), grehlin is causing us to crave more food; the prefrontal cortex is telling us that all the effort that we are putting in is not working, and cognitive dissonance indicates that we might not even want to reach the number on the scale as much as we thought we might like to! Cue binge eating to de-rail any small results which we first noticed, and a failed diet to boot.

It is not all bad news, though: with the knowledge of the methods that our brains use to de-rail us, it is possible to harness some of these processes to our advantage (and begin to fail-proof our dieting dilemma). Some of these are listed below, but include making firm written goals with smaller achievable targets along the way, describing why and how much you want to achieve your weight loss.

Tips and tricks to ‘fail-proof’ your diet:

  1. Write down your goal- Researchers say that the simple process of writing down your goal makes you more likely to achieve it. This can help make you accountable

  2. Write down smaller goals, mapping your achievements, within your ultimate goal- This can help to overcome the cognitive dissonance. Perhaps you might even consider some fitness goals or non-scales victories, such as enduring the morning coffee shout without a citrus slice

  3. Resist adopting an ‘all or nothing’ mentality- Do the best you can, and do not let a slip-up here and there de-rail the whole process. Further to this: filling your plate high with greens can help keep you feeling full and not deprived! Remember that foods that are less calorifically dense take up more room on your plate than fast food and junk foods.

  4. Get enough sleep- To keep your mind and body sharp and focused as you work towards your goals. Read my post on sleep and gains.

  5. Mindfulness- Use your mind, specifically your prefrontal cortex, to your advantage. Write down every reason why you want to achieve your weight loss goals, and what differences that you will see in your life as a result of reaching your goals. Using the prefrontal cortex as your tool you can harness the effectiveness of these imagined scenarios to motivate you to SUCCESS!

Perhaps we can better explain why diets fail when we investigate how the definition of ‘diet’ has changed. Diet from the dictionary definition is a descriptor for what we eat everyday. However the connotations of the term might better help to explain the fundamental problem of diet failure: the word’s connotation implies adopting an eating regime hinged on restriction for the sole purpose of changing one’s outward appearance. This mentality fails us, however, because it is a decision made in the short-term, forming expectations for instant results. This approach is neither sustainable, or logical.

Read the rest of my blog for all things fitness, Check my Ebooks, and reach out to chat!

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