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The science behind food cravings.
Food craving can be defined as an intense, conscious desire to consume a specific type of food. Typically, this specific type of food is energy-dense , high in calories, sweet and savoury which creates a feeling of “reward” in the brain.
But Why do we have food cravings in the first place?
Is it because the body is in some kind of a nutrient / energy deficit and is trying to make up for it?
Numerous studies conducted over time refute this hypothesis.
Cravings are believed to be more of a psychological phenomenon than a physiological one. How they work is a difficult science to understand. It is however important for anyone who wants to lose weight for good.
First let us understand the basic psychology behind cravings.
The most compelling psychological theory that explains this phenomenon is: (Pavlovian) conditioning.
According to this theory, if a cue or an act is repeatedly paired with food consumption then that act can eventually elicit a desire to eat (conditioned response) on its own.
For example, let’s assume that while watching my favourite TV show, I order take out most times. This cue (watching my favourite TV show ) gradually becomes associated with eating non home cooked food .Over time, just the look of my favourite TV show, elicits a desire to order a pizza or noodles. The same circuits apply for craving popcorn and coke at the theatre. It’s genius actually because most fast food companies exploit this very trick to earn millions around the globe.
Several laboratory studies have examined this Pavlovian theory of food cue reactivity by repeatedly pairing an inherently neutral cue with energy dense foods , and comparing the responses to this cue with the responses to another stimulus which is never followed by food intake.
A consistent finding in these experiments is that after conditioning, the cue always evokes conditioned responding. This is reflected by heightened psychological (e.g., explicit eating expectancies, eating desires) , psychophysiological (e.g., salivation) and behavioural responding (e.g., approach tendencies, place preferences, food intake/choices).
Theoretically, any neutral / inert cue can become a conditioned stimulus, if repeated multiple times. For example,
In real life, relevant cues are internal states such as bad mood, period hormones and extreme emotions; external states such as time of the day , binging on a TV series, a movie night, a drive through on the way to / from work, stress at work and so many more.
Essentially, our food cravings are a by-product of our own conditioned stimuli — our own actions — accumulated over a period of time.
Many factors can aggravate craving for calorie dense foods and if you are on a journey to get fit, like me, this can be a problem. Therefore I feel it is important to stay away from practices that feed the craving monster.
There is a classic study by Herman and Mack, in which restrained eaters showed an uninhibited eating behaviour (they reported a higher ice cream consumption) after consumption of a preload (milkshake), whereas so-called unrestrained (“normal”) eaters decreased their ice cream consumption after consumption of a milkshake.
This effect was concluded to stem from the fact that restrained eaters had violated their dietary rules by consumption of the milkshake, which led to a “what-the- hell-effect” and loss of inhibition.
Different experimental studies since then focussed on the association between food cravings and selective food deprivation. Participants were instructed to refrain from eating certain types of food. Consumption of all other foods was unrestricted and, thus, total energy consumption was unaffected.
Almost all studies found that deprivation increased the craving for the avoided foods.
As none of these studies imposed a restriction on any foods other than the avoided foods or on the total caloric intake, it seems that perceived deprivation — the feeling of not eating what or as much as one would like, despite being in energy balance — plays a larger part in generating food cravings than actual nutrient deficiencies.
The scientific community examined the other group of individuals as well — those on weight loss interventions, who consumed less food overall but did it willingly, thus not feeling deprived.
Some of these interventions were: Low-carbohydrate diet (1500 kcal/day), Low calorie diets (750 kcal/day deficit from baseline energy requirements), Very low-calorie ketogenic diet (600–800 kcal/day during the first 60–90 days), Group behavioural weight loss program with a structured meal replacement (1000–1200 kcal/day between weeks 2 and 12), Energy restriction (25% decreased energy intake from energy requirements), High-protein or high-carbohydrate diet (1500 kcal/day).
The results from all these studies are completely opposite to the findings from selective food deprivation studies.
A meta-analysis of these studies found that food cravings actually decrease from pre- to post-intervention or during the apparent caloric restriction period. These decreases seem to occur primarily during the first weeks of caloric restriction and do not seem to rebound at later follow-up measurements.
The reason for the decrease in food cravings during caloric restriction may be
1. Due to extinction of previously acquired conditioned responses.
If I stop eating take out while watching my favourite show and substitutes it with a home cooked meal of lentils and rice, the initial habit loop starts to be overwritten. The new cue has to be repeated multiple times though.
Moreover, it has been seen that a reduced frequency (but not the amount) of consuming craved foods related to reductions in cravings for these foods .
That is, to avoid cravings — one should not eat certain foods over a prolonged period of time — at least several weeks as this may decouple learned associations (e.g., between evening time and tea consumption) so that the cue (e.g., evening time) no longer triggers a conditioned response (e.g., craving for tea).
2. The individuals on weight loss interventions did not have a perceived deprivation.
This means that if you want a healthy relationship with food, or if you want to lose weight, it is necessary to never give up on your favourite foods completely.
Rather, decouple the food from the cue. Have pizza without binge watching a series. Have tea and a sandwich at the theatre and not popcorn and coke.
Repeat till the cue is no longer associated with a particular food.
The cue could still be associated with food — but then you would be empowered with the ability to make better choices.
And that is what it all comes down to in the end —
The ability to chose well for your health.
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