The quest to measure food addiction
Measuring a concept, or an entity, is crucial to fully understand it.
It is not a surprise that scientists have tried to measure food addiction – either in terms of its brain correlates, or of behaviours.
There are some questions that need to be answered: are the neurobiological correlates of food addictions similar to the ones of other addictions? Are these results found in humans as well as in animals? And are psychological and behavioural measures in humans able to identify food addiction and distinguish them from other phenomena?
In the last article of this week we will discuss some approaches, and what was found by studies that adopted them.
Biological measures of food addiction
For many years, neurobiologists have been trying to identify and measure the biological markers of addiction in animal models.
For instance, abnormally high concentrations of a specific protein, called Delta FosB, in the dopamine neurons of the nucleus accumbens, seem to be enough to cause the symptoms of addiction. Measuring the concentration of Delta FosB, and the alterations of neurotransmitters in reward areas, could then prove that high sugar or high fat foods can indeed behave as “addictive” substances. Some studies on animals (such as Peter Olausson and others, 2006, or Wallace and others, 2008), found results pointing in that direction, but, as of 2018, we aren’t aware of studies unequivocally pointing out elevated levels of this protein in the brain of humans showing traits of food addiction.
What about the study we cited in the last video, and in general neuroimaging studies? This kind of study can detect changes in the volume or in the structure of the brain at a relatively large scale. fMRI studies can investigate the activity of brain areas but have a spatial resolution of a few millimetres. Smaller structures can’t be clearly seen or can’t be seen at all. This does not mean that MRI studies are worthless, but it does mean that they would need to be supported by other kinds of evidence if we want to accurately “translate” to humans the results obtained in animal models.
Psychological measures of food addiction
To measure addiction like behaviour in humans, scientists have devised tools such as the YFAS, or Yale Food Addiction Scale.
The Yale Food Addiction Scale is a retrospective self-report instrument which means that people rely on their memory and their beliefs to fill in the required information, and there is not another person that assesses them.
This approach has its own advantages: the quiz is easy to administer, is quick and can easily be used in research. Studies that used it found that, for instance, people with higher self-reported levels of food addiction had higher body mass indexes and ate more energy-dense foods like sweets (Kirrilly and colleagues, 2015).
Scores in the Yale Food Addiction Scale also correlate with binge eating, and with emotional eating, a concept that will be introduced by Prof. Stroebele-Benschop in the next week.
The Yale Food Addiction Scale and similar tools can help us identify people whose behaviours are suggestive of a food addiction. They have been validated as research tools and they might be useful in designing psychological and psychotherapeutical treatments tailored on the single individual.
But we must be careful: in the same words of the authors, “the Yale Food Addiction Scale is not sufficient evidence that food addiction exists” (Meule and Gearhardt, 2014), but “it does provide a standardized tool to identify individuals who are the most likely to be experiencing an addictive response to food.” (ibidem)
The Yale Food Addiction Scale – and its scoring instructions – can be found here, along with its scoring instructions.
We ask you to take a moment to read it and reflect on the questions it poses before moving on to the next step.
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