Deciphering the drivers of appetite to support a healthier diet
In recent decades the developed world has benefitted from a significant increase in the amount and variety of readily available food. But this abundance of food, often high in fat and sugar, may be also contributing to an increase in obesity.
Closely associated with conditions such as type 2 diabetes and cardiovascular disease, obesity is now a major public health concern. At the other end of the spectrum, the elderly and those recovering from trauma can often suffer from a debilitating or even potential life-threatening loss of appetite.
FULL4HEALTH is a pioneering research project investigating how feelings of hunger and fullness work in humans, how they affect our eating behaviours in ways beyond our conscious control and how they can result in long-term ‘energy imbalance’ – that is, an intake of calories which is either too great or too little in relation to the energy we actually expend.
The appetite control process begins with the release of hormones by the gut in response to food consumption. These hormones send one set of signals to the brain. Another set of signals, meanwhile, is sent by the body’s fat deposits to indicate how much energy is already stored. As the brain starts to interpret these signals, it is being assailed by yet another set of ‘higher level’ psychological signals such as those relating to our sense of pleasure or reward.
“This all makes for a complicated ‘food-gut-brain’ interrelationship,” explains FULL4HEALTH’s Project Coordinator, Professor Julian Mercer of Aberdeen University’s Rowett Institute of Nutrition and Health in the United Kingdom. “One of the key areas of the project is therefore the assessment of people’s interactions with food at a number of different levels – psychological, metabolic, physiological and neurological,” he says.
The complex pattern of links between food, gut and brain helps explain why voluntary attempts to diet frequently fail. They are fighting against these deeper gut-brain responses. The work of the FULL4HEALTH team is thus a significant step towards designing a radical new approach to the way we manage weight control and its associated health impacts.
Sheer human variety, however, means this can not be a ‘one-size-fits-all’ approach. For this reason, a core feature of the FULL4HEALTH project is that it is examining how our responses to food, together with the resulting gut-brain signals and their integration, vary at different periods of our lives. For the first time in a single study, the project team is comparing four distinct age groups – children, adolescents, adults and the elderly. The team is also looking at differences between men and women and between lean and overweight body types.
Specific factors being investigated by FULL4HEALTH project include the effect of differing food structures and textures. Protein, for example, is known to create more of a sense of ‘fullness’ than carbohydrate or fat, suggesting there is scope to use different food types to help regulate the appetite. The project is also studying areas of the brain that have received little attention in the past for their role in the food-gut-brain relationship. Whereas much attention has focused on the hypothalamus – the part which regulates energy balance – the FULL4HEALTH team is studying the role played by other sections, including the rear portion of the brain where nervous and other signals from the gut converge. The influence of pleasure as a driver of appetite and the way hormones produced by the gut affect this is another important area of focus.
It is expected that the greater understanding of the mechanisms of appetite control that will be generated by FULL4HEALTH will prove valuable on several levels. “As well as providing a basis for better-informed policymaking, it will also help individuals take better control of their own eating habits,” says Professor Mercer, “and it will support the food and drink and pharmaceutical industries to harness the food-gut-brain dynamic as a basis on which to develop foods, diets, supplements or drugs to promote healthier lives,” he concludes.