Investigating the mechanics of hunger and satiety
Over half the EU adult population is now overweight or obese. The rate of obesity has more than doubled in the past 20 years in most EU member states, a report published late last year by the European Commission and the OECD found, with one in seven children in the EU currently overweight or obese.
The obesity epidemic is a public health challenge throughout Europe, and Scotland – where obesity-related deaths have increased by over 40 per cent since 2004 – is by no means immune. However, while other European countries are experiencing the same problem, it is not on the same scale as in Scotland.
Obesity is “particularly acute” in Scotland, says Professor Julian Mercer, head of obesity and metabolic health at the University of Aberdeen Rowett Institute for Nutrition and Health.
He explains: “I suspect most people would agree it is our lifestyle that is driving it. We do tend to be less active than some countries… and also we have quite a poor diet here in Scotland and I think the combination of the two – a poor diet with lots of fairly dense food going in and relatively low levels of activity – is driving us into a positive energy balance, which is what obesity is.” At present, the overall cost of obesity to Scottish society is around £457m each year; a figure which, if left unchecked, is estimated could reach over £3bn a year by 2030. The levels of overweight and obesity in Scotland are “a serious concern”, the Scottish Government admits in its obesity strategy, which marked its first anniversary last month. In ‘Preventing Overweight and Obesity in Scotland: A Route Map Towards Healthy Weight’ it notes that overweight and obesity pose real risks to the health of the Scottish population, while the burden of disease that accompanies them also hinders our ability to achieve sustainable economic growth.
Mercer praises the Scottish Government for being “very engaged” and recognising that this is an issue with far-reaching consequences.
He argues that Scotland’s experience of the disease provides an “extra impetus” to develop strategies to tackle the problem.
Last month it was announced that the research team at the Rowett Institute will take the lead on a major international study that aims to piece together what goes on in our body to make us feel full or hungry. The €9m European Union-funded ‘Full4Health’ project brings together scientists from 19 European labs, with researchers from Aberdeen joining partners in the UK; Greece; the Netherlands; Norway; France, Germany and Denmark.
The fact that it is being coordinated by the team in Aberdeen is “quite a coup” for Scotland, Mercer says.
“Three of the partners are actually from Scotland so that is a big success story as far as we are concerned,” he adds.
The five-year project will look at mechanisms of hunger and satiety, and will strive to fill the gaps in our understanding of the relationship between food, the gut and our brain.
Mercer explains: “Although there is quite a lot of work on the gut brain signalling and we know quite a lot about how the gut signals the brain, food is kind of the silent partner in this in terms of our understanding of this.
We don’t really know how food interacts with that signalling system. So what the project is really about is trying to understand that better. How does food interact with that physiological system which we all have in our bodies and is there potential for manipulating the diet to actually exploit that physiological system one way or the other, to either limit intake or enhance it where there is a problem with malnutrition.” Another important thread of the work will be investigating how our body responds to food at different stages in our lives.
“In our human nutrition unit we tend to recruit overweight, middle-aged men as they are an easy to get to population – they come along because they want to lose weight. But one of the things that was in the EU call was that they wanted to know how interactions with food take place across the lifespan. So we have four age groups in the study ranging from children as young as eight years of age up to people at 75 years of age in the older age group.” A long-term goal of the project is to find a food solution to help with the problem of inappropriate over-consumption of calories that exploits the physiology we already have, rather than working against it.
“I think most people think a diet is something you are destined to fail on because you are fighting against the fact that you are hungry. That is the biggest thing. It ends up being rather monotonous so it is hard to stick to. So most people’s experience of a diet is that they are unsuccessful, unfortunately.
“But the problem then is if the diet is effectively caloric restriction then you are fighting against your physiology all of the time. Your physiology starts to worry about what is going on. It makes you very hungry, which is miserable – well, I’ve never been on a diet so I wouldn’t be able to comment – but it makes you miserable and feel bad and through time what happens is your body starts to worry about it sufficiently that it starts to reduce your energy expenditure. So even though you are on a diet, your weight loss tails off. So most people’s experience is initial weight loss, which is gratifying, and then it tails off and of course you are still on a diet and still really hungry but you don’t seem to be getting anywhere and that is when people tend to give up. And then what happens is because their body has activated the mechanisms which are essentially there to preserve life against starvation, you tend to overshoot so you end up heavier than you started off. That is the physiology. So most people’s view of a diet is that.
“We need to move away and say we ought to be thinking about a diet which actually doesn’t have that connotation, something that you could stay on for years, maybe, but is actually giving you some support in terms of trying to, in the case of overweight and obesity, help you to naturally restrict your caloric intake.” There are “no quick fixes” to be found here, he cautions, and says that “the likelihood of there being a magic bullet is, I think, quite remote.” Instead, he argues it is important to strive for sustainable, healthy, enjoyable dietary strategies.
“Ultimately food is a rewarding thing for humans and probably most animals as well.
You could probably get people to control their weight by going back to feeding them herrings, oatmeal and potatoes every day, 365 days a year but we are not going there – I don’t think! We have to recognise that people enjoy food so what we need to come up with is some way of enabling them to enjoy the food they are eating but actually not over consume.” While substantial time and money and media attention has been invested in the quest for a cure-all pill, Mercer argues this is the “least likely” solution.
“A pill isn’t going to do it because it is not going to be enjoyable; people aren’t going to want to do that. Unsurprisingly. Why would they?” Moreover, do we really want half the population taking drugs for the rest of their lives, he asks.
“I think we actually need to be pragmatic and say there are going to be lots of different potential ways of addressing this and we need to keep all the clubs in the bag at the moment. So we want to have the community interventions getting people involved and more knowledgeable about what is happening and what they can do about it. We need to look at drug treatments and potential surgical interventions but the one thing we could really do with a lot more bolstering of is this idea that we should address the food option, because it is the food we take in that is driving obesity, effectively, because it is an energy surplus.” The potential to reformulate food with a higher protein content that gives it some enhanced satiety property is a real possibility, not science fiction, he says, and warrants greater exploration. And he is hopeful that at the end of the project they will have identified some potential areas for manipulation.
“Ultimately we would like to be able to harness the power of our natural physiology, and our complex interactions with food, to demonstrate the potential of a food solution to the health problems of over- and underconsumption of calories throughout our lives.”