Thursday September 11 2014
Eating stimulates reward pathways in the brain
“Food is not addictive ... but eating is: Gorging is psychological compulsion, say experts,” the Mail Online reports.
The news follows an article in which scientists argue that – unlike drug addiction – there is little evidence that people become addicted to the substances in certain foods.
Researchers argue that instead of thinking of certain types of food as addictive, it would be more useful to talk of a behavioural addiction to the process of eating and the “reward” associated with it.
The article is a useful contribution to the current debate over what drives people to overeat. It’s a topic that urgently needs answers, given the soaring levels of obesity in the UK and other developed countries. There is still a good deal of uncertainty about why people eat more than they need. The way we regard overeating is linked to how eating disorders are treated, so fresh thinking may prove useful in helping people overcome compulsive eating habits.
Where did the story come from?
The study was carried out by researchers from various universities in Europe, including the Universities of Aberdeen and Edinburgh. It was funded by the European Union.
The study was published in the peer-reviewed Neuroscience and Biobehavioural Reviews on an open-access basis, so it is free to read online. However, the online article that has been released is not the final one, but an uncorrected proof.
Press coverage was fair, although the article was treated somewhat as if it was the last word on the subject, rather than a contribution to the debate. The Daily Mail’s use of the term “gorging” in its headline was unnecessary, implying sheer greed is to blame for obesity. This was not a conclusion found in the published review.
What kind of research was this?
This was not a new piece of research, but a narrative review of the scientific evidence for the existence of an addiction to food. It says that the concept of food addiction has become popular among both researchers and the public, as a way to understand the psychological processes involved in weight gain.
The authors of the review argue that the term food addiction – echoed in terms such as “chocaholic” and “food cravings” has potentially important implications for treatment and prevention. For this reason, they say, it is important to explore the concept more closely.
They also say that “food addiction” may be used as an excuse for overeating, also placing blame on the food industry for producing so-called “addictive foods” high in fat and sugar.
What does the review say?
The researchers first looked at the various definitions of the term addiction. Although they say a conclusive scientific definition has proved elusive, most definitions include notions of compulsion, loss of control and withdrawal syndromes. Addiction, they say, can be either related to an external substance (such as drugs) or to a behaviour (such as gambling).
In formal diagnostic categories, the term has largely been replaced. Instead it is often changed to “substance use disorder” – or in the case of gambling “non-substance use disorder”.
One classic finding on addiction is the alteration of central nervous system signalling, involving the release of chemicals with “rewarding” properties. These chemicals, the authors say, can be released not just by exposure to external substances, such as drugs, but also by certain behaviours, including eating.
The authors also outline the neural pathways through which such reward signals work, with neurotransmitters such as dopamine playing a critical role.
However, the authors of the review say that labelling a food or nutrient as “addictive” implies it contains certain ingredients that could make an individual addicted to it. While certain foods – such as those high in fat and sugar – have “rewarding” properties and are highly palatable, there is insufficient evidence to label them as addictive. There is no evidence that single nutritional substances can elicit a “substance use disorder” in humans, according to current diagnostic criteria.
The authors conclude that “food addiction” is a misnomer, proposing instead the term “eating addiction” to underscore the behavioural addiction to eating. They argue that future research should try to define the diagnostic criteria for an eating addiction, so that it can be formally classified as a non-substance related addictive disorder.
“Eating addiction” stresses the behavioural component, whereas “food addiction” appears more like a passive process that simply befalls the individual, they conclude.
There are many theories as to why we overeat. These theories include the existence of the “thrifty gene”, which has primed us to eat whenever food is present and was useful in times of scarcity. There is also the theory and the “obesogenic environment” in which calorie dense food is constantly available.
This is an interesting review that argues that in terms of treatment the focus should be on people’s eating behaviour – rather than on the addictive nature of certain foods. It does not deny the fact that for many of us high fat, high sugar foods are highly palatable.
If you think your eating is out of control, or you want help with weight problems, it’s a good idea to visit your GP. There are many schemes available that can help people lose weight by sticking to a healthy diet and regular exercise.
If you are feeling compelled to eat, or finding yourself snacking unhealthily, why not check out these suggestions for food swaps that could be healthier.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.