‘Brain food’ - the neurobiology of appetite and addiction
The next in our
series of 'in depth' interviews, with key people in the field, looking at their
work and what it says about the future of applied neuroscience.
Suzanne Dickson is Professor of Physiology and Neuroendocrinology at the Sahlgrenska Academy, University of Gothenburg, Sweden. A leading figure in the neurobiology of appetite, her work has particular focus on how food intake and feeding behaviour is controlled. Much of her emphasis is on the effect of endocrine and metabolic signals, chiefly ghrelin – a gastrointestinal hormone recognised as having a major influence on energy balance.
“Obesity is a brain disorder. It is about over-eating,” Professor Dickson told ECNP as she framed the importance of this kind of research. “Whatever the underlying cause, whatever you can say about it, it involves the brain. We don’t know the extent to which some people are born with some form of defect in brain pathways important for feeding control, or whether they develop this later in life, but once you are obese, maybe the obese brain can never become normal again.”
Turning to her work with ghrelin in particular, she noted that there are two important sites in the brain known to respond to the hormone’s action. “One concerns energy balance in the hypothalamus – it learns whether you need to eat or not for your long-term fat stores, and then it tries to do something about it, to adjust it, to keep control.
“But the second key site is the mesolimbic reward area in the brain. A few years ago we discovered that ghrelin also targets the dopamine system, linked to reward behaviour. Then we went on to work out what that is good for. By proof of concept we did some work with alcohol reward, and showed that you needed ghrelin to signal for alcohol reward. But we have gone on to show that it is important for reward from food, and craving-like behaviours for food in actuality.”
Professor Dickson has been involved in several projects in recent years that have striven to understand more about the relationship between food, eating and the brain. Of particular note is NeuroFAST1, a 13-centre European research consortium exploring the neurobiological and psychological underpinnings of habit-forming and addictive food behaviour.
Funded by the EU Seventh Framework Programme (FP7), one of the key aspects of the project has been assessment of the validity of so-called ‘food addiction’. “When we examined the evidence, we did not find any indication for such a thing as ‘food addiction’, because that would suggest that food acts like a chemical that acts on the brain to cause us to become addicted – but that is unfounded,” said Professor Dickson.
“Therefore ‘food addiction’ is kind of a misnomer for a behavioural disorder, and one that we thought should be relabelled as ‘eating addiction’ instead.”
Indeed, she added that food addiction, should it exist, would also be expected to follow the more classical characteristics of addiction, including tolerance development and emergence of withdrawal symptoms. Without these aspects, ‘eating addiction’ is a term with much more applicability, but one which still carries additional questions as to its driving mechanisms.
With this in mind, Professor Dickson talked through the balance between the body’s instincts to nourish and survive, the importance of novelty in food, and the blurred lines of reward and addiction. “If you have a food that you really like, and then have repeated exposure to it, you will get a kind of habituation, and the reward response will diminish over time,” she said. “But that is not the same with cocaine or alcohol. There you get a dopamine response every single time. It comes down to survival – we need to ingest a variety of foods from our environment.
“The reward system does respond to food, but what is the difference between reward and addiction? There is an enormous difference, which must involve some sort of reprogramming of certain pathways, but we don’t really understand that yet. We don’t understand it for alcohol, and we have even less information on food.”
In the era of inexpensive convenience foods, many of which can be inherently unhealthy or heavily calorie-ladened, the choice to eat sensibly can be difficult. With obesity and other morbidities on the rise, the Nudge-it project – an interdisciplinary mission spanning several neurological, modelling, economic and policy areas – is tasked with developing and implementing scientific approaches to better tackle ‘comfort eating’ and other issues involved in poor dietary health2.
With the University of Gothenburg being one of the Nudge-it partners, Professor Dickson has been involved in exploring how best to ‘nudge’ people into making better food choices. “It is quite a big project with diverse arms,” she said. “My role in the project has been to look at whether, if you’re exposed in early life to a bad diet, does that change your food choice and your food behaviour when you become an adult? We are doing that work of course in rodents, and we are quite interested in an answer, i.e. just how much you can influence long-term behaviours by early-life manipulation.”
Professor Dickson continued, looking to possible clinical benefits of a better understanding and control of dietary choices: “I think dietary choice is a kind of uncharted landscape in obesity research, for example, because it is so difficult to study it. But I think it is important to examine how preferences are built in the first place, and how life-long experiences shape them.”
Novel approaches showcased in Vienna
At the 29th ECNP Congress in Vienna this year, Professor Dickson will moderate an educational session that will dissect novel treatment approaches for eating disorders. In the session, Roger Adan (the Netherlands) will touch upon translational approaches in obesity treatment, while Janet Treasure (UK) will dive into novel brain-directed strategies for eating disorders.
From the panel, Professor Dickson will no doubt offer her perspectives for the audience, but she is also very keen to see her fellow colleagues present the latest insights throughout the programme. “I’m looking forward to the congress because I am hoping to hear some updates!” she said in closing.
The session ‘E.03: Novel treatment approaches for eating disorders’ will take place at 15.00 on Sunday 18 September during the 29th ECNP Congress in Vienna.
1. Hebebrand J, et al. “Eating addiction”, rather than “food addiction”, better captures addictive-like eating behavior. Neuroscience & Biobehavioral Reviews, 2014;47:295-306
2. Nudge-it. www.nudge-it.eu