Over-consumption of calories relative to energy expenditure, and the consequent development of overweight and obesity, is responsible for much of the burden of chronic disease in the developed world. Even quite modest amounts of weight loss can have a substantial beneficial effect on morbidity and mortality, reduce healthcare cost burden and improve metabolic health profile. Reducing caloric intake, coupled with a healthier lifestyle, is the most effective route to this goal. Thus, understanding the mechanisms of hunger and satiety and how particular foodstuffs and nutrients affect them is important for evidence-based interventions to achieve weight loss. A number of key messages have been identified from the unique European Union (EU)-funded project, Full4Health. One aim of the grant was to describe food-gut-brain interactions in the regulation of appetite across the lifespan. We investigated this in a large nutrition intervention study applied in four different age groups (children, adolescents, adult and elderly), the two sexes (male and female) and two different weight categories (normal and overweight/obese). A secondary aim was to examine the role of a protein-based breakfast on short-term appetite control. In order to achieve this, we studied 391 subjects across Aberdeen (University of Aberdeen, Rowett Institute of Nutrition and Health) and Athens (Harokopio University, Department of Nutrition & Dietetics), as 103 children (8 to 10 years), 109 adolescents (13 to 17 years), 97 adults (25 to 45years) and 82 ageing adults (65 to 75 years) in a within-day dietary intervention study. Some key observations included:
• Important Role of Breakfast for Appetite Control
We live in an “obesogenic environment" where the working population eats up to two meals a day at a desk, and this often includes eating breakfast “on the go." Our lifestyle choices associated with eating behaviour and physical activity contribute to the development of obesity. Reversing the effects of obesity is a huge challenge—and understanding the role of food, energy and nutrients at breakfast time on appetite and energy balance is essential to develop dietary strategies for both the prevention and treatment of obesity. We report that consuming a breakfast high in protein in adults appears to mediate both peripheral signals via the gut hormones (GLP-1 and PYY), and central appetite control (assessed by fMRI scans).
• Appetite Across the Lifecourse
The impact of breakfast consumption on appetite control and energy balance across the lifecourse in young children to elderly. In general, subjects were able to detect a reduced calorie load when provided a breakfast drink below body weight maintenance (weight loss drinks), increasing energy intake to at least partially compensate for the lower breakfast calorie intake. However this increased ad libitum energy intake three hours after breakfast was insufficient to compensate in calories, for the reduced energy content at breakfast, for any age group. All age groups consumed more at the snack buffet after drinks provided at weight loss amounts (below calorie requirements), in comparison to the larger weight maintenance drinks, fed to calorie requirements. Although we assessed subsequent ad libitum snack intake three hours after breakfast, and reported significant differences between the drinks (meals), we did not measure 24-hour energy intake, so it may be that further compensation may have occurred later in the day. This work indicates daily energy balance is not tightly regulated, and dietary manipulations at breakfast can be part of a dietary strategy to influence body weight (either for weight loss or gain). It is of further interest that the elderly subjects were less responsive to breakfast choice, and further work would need to explore the reasons for this.
• Protein Supply for Healthy Ageing
Few studies have addressed appetite control of the elderly and how to deliver food to maximize nutrition. Our additional cohort on lean, normal weight and obese subjects gives invaluable insight to appetite control, in particular for designing foods for specific situations such as poor appetite in elderly patients. It is a challenge to maintain adequate nutrition in the lean elderly, and the current work supports the role of protein drinks at breakfast to provide additional nutrition, without compromising food intake later in the day. This is an important finding on appetite that is relevant for clinical practice. The data suggest that providing a liquid (dairy-based) high-protein breakfast meal for elderly subjects is a beneficial strategy for appetite control, in the short-term at least.
• Food-Gut-Brain Axis Important to Influence Food Intake
Taken together, the research findings contribute to building a foundation for the identification of targets for lifestyle and therapeutic interventions in obesity. Ongoing research will further our understanding of the effects of obesity on body weight homeostasis and potentially enable us to exploit, at least for some obese individuals. The gastrointestinal (GI) tract has important endocrinological functions in the regulation of energy intake and appetite, and the effects of gut hormones involved in the regulation of appetite can be a target for future food approaches. Hormones secreted from the GI tract—including the orexigenic hormone ghrelin and anorectic hormones peptide YY (PYY), glucagon-like peptide 1 (GLP-1)—all play a role in the control of appetite (that is, satiety and food intake).
Alexandra Johnstone, Ph.D., is a senior research fellow and registered UK nutritionist based at the Rowett Institute of Nutrition and Health, University of Aberdeen. She leads internationally competitive research in the area of human appetite control in the context of weight loss. More recent work has been on the role of high-protein diets in health. Johnstone acts as a consultant for the media and food sector at local, national and international levels. She has regular interactions with policy makers and advisors, and parliamentarians, particularly through her EU-funded work. She is a partner in three EU grants in Framework 7 (SATIN, Full4Health and NeuroFAST).
With more than 20 years of experience in obesity-related research, Julian Mercer, Ph.D., is currently theme leader of obesity and metabolic health research at the Rowett Institute of Nutrition and Health, University of Aberdeen, and a member of the institute executive committee. He leads the consumer choice, diet and health workpackage in the Scottish Government’s current Healthy, Safe Diets strategic research programme, and is theme co-ordinator for food, health and wellbeing for the upcoming (2016-2021) programme. He is also co-ordinator of the EU FP7-funded Full4Health project, and a partner in two further FP7 projects, NeuroFAST and SATIN.