Animal models appear to show that certain
foods (usually the so-called “high-fat, high-sugar and high-salt foods) can be
addictive. However, this experimental model of addiction bears no relationship
to addiction in humans. In his book “An End to Over-eating”, David Kessler
comments on this animal model of food addiction, one he incidentally finds
attractive to human obesity. Citing work from Italian researchers, which showed
that in the short term, a cheese flavoured snack food increased levels of
dopamine in rat brains he writes thus: “Over
time, habituation set in, dopamine levels declined and food lost its capacity
to activate their behaviour. But there’s more to the story. It turns out that
if the stimulus is powerful enough, or administered intermittently enough, the
brain may not curb its dopamine response after all. Desire remains high. We see
this with cocaine use, which does not result in habituation”. Effectively one
can trick the mouse and then make a quick jump to human cocaine addiction.
Simple isn’t it?
Not so, according to a recent review by
researchers at the Department of Psychiatry at the University of Cambridge[1],[2]
In their review, they begin by distinguishing between behavioural addiction
such as gambling, which doesn’t have an additive agent (betting slips per se
are not addictive) and substance addictions, which are agent-dependent. Alcohol
and cocaine are examples of agents that can be addictive. Thus the first
challenge to the food addiction model is to identify the agent. It can’t be “fat”
since effectively a totally fat-free diet is lethal to populations –
reproduction becomes impossible. It can’t be “high-fat” since olive oil, the
elixir of all our ailments according to many, is pure, 100% undiluted fat ~ the
real thing. The normal brain relies solely on glucose as a fuel so if “sugars”
are the agent, we have a problem. If it’s a specific cocktail of
fat-sugar-salt, then that needs to be articulated in terms of the human diet
and as of now, no such norms exist, let alone exist in some unproven state. So
the putative addictive agent in food is utterly ill defined. The authors go on
to point out that the so-called addictive hyperpalatable foods are widely
available and widely consumed but as yet, are not a widespread public health
problem. Thus they argue that in addition to some vague and as yet undefined
cutoff above which addiction may occur, they will have to find other factors to
explain why some people might become addicted whereas others will not. It could
be a genetic factor or an addiction, dependent on alcohol intake, or on a
sedentary life style or on stature or age or gender or all of the above. The
concept of food addiction, particularly in relation to obesity might be popular
with the wannabe celeb scientists but it is as imprecise a concept as one could
possibly imagine.
The
clinical management of addiction uses a standardised guideline to define
substance dependence based on the “Statistical Manual of Mental Disorders,
fourth edition (DSM-IV)”. There are 7 criteria to be considered within this
tool, all of which help in judgment on addictions. The first deals with “tolerance” and specifically the need for the
user to seek ever-increasing amounts to reach the desired level of
intoxication. This is impossible to apply to food addiction since we know
neither the exact agent or its dose or its physiological, genetic, social or
lifestyle dependencies. The second
relates to withdrawal symptoms and no such data exists for humans and their
food habits. The manual refers to symptoms such as shakes and sweats! The third is a persistent desire for
and unsuccessful attempts to cut drug use. Overweight persons certainly wish to
rid themselves of excess fat and try repeatedly to do so but linking this
concept to a specific and putative food addiction agent is not supported by
scientific data. The fourth
describes the taking of larger amounts of the drug than intended. This is
impossible in food since we don’t know the agent or its intoxicating dose. The fifth recognises that a great deal
of time is spent getting, using and recovering from the drug. Take a walk in
Tesco or Wal-Mart! The sixth deals
with the effect the drug has on the pursuit of important social, occupational
or recreational activities. It’s hard to
think of work absenteeism arising from the pursuit of highly palatable and
putatively “addictive” foods. The
seventh and final area deals with the continued use of the drug with the
user well aware of its dire consequences for health and social well-being.
Again, it is impossible to see how this can apply to food.
The authors do however, point out that
certain eating patterns are nearing the DM-IV criteria, most specifically Binge
Eating Disorders (BED) which they say is characterized by: “ …recurrent episodes (‘binges’) of uncontrolled, often rapid consumption
of large amounts of food, usually in isolation, even in the absence of hunger.
This eating behaviour persists despite physical discomfort and binges are often
associated with feelings of guilt and disgust”. This is the closest that
psychiatrists see food as approaching addiction but researchers in Yale are
working on an adaptation of DSM-IV to score and quantify food addictions[3].
This blogger’s read of this adaptation of the DSM-IV clinical guidelines is
that it will be quite significant adaptation, if not a total re-write. Like it
or not, this will sustain the nutrition-psychiatry gulf in understanding and
characterizing addiction.
Food addiction has now begun to attract the
interests of other groups, most notably the legal & ethical researchers[4].
If, and it is a big if, research were to point to a possible addiction among
some to a particular food or nutrient or cocktails thereof, then how do we deal
with this legally? Do we expect to see certain foods removed from the supermarket
shelves and driven into the underworld of dodgy dealing such as the illegal
cheesecake (high fat, high, sugar, High salt food par excellence) the Cambridge
scientists refer to? Of course this is farcical but where else would a
regulatory and policy framework go to tackle this problem, if indeed, such
behaviour is deemed to be a problem in the first place? For those who want to explore this further,
watch the You Tube video of a stand up comedian (lead author of references
1& 2 above) who is also a board certified psychiatrist on the subject of
food addiction[5].
