Does flavour-nutrient inconsistency compromise energy regulation in humans?

The modern invention of processed foods has fundamentally changed our food environment. Retailers now stock an extremely wide range of foods. Even single types of food (e.g., pizza) are now available in numerous varieties that differ in size and the number of calories that they contain. For example, our data show that the number of calories in fish pie 'ready meals' can vary by up to 450% in the UK. In animals, this kind of 'variability' promotes overeating and an increase in body weight. For the first time, this project will explore whether this also happens in humans. There are two ways in which variability in our food environment might increase the number of calories that we consume. These are summarised below. In PHASE 1 we will look at our capacity to 'compensate' for calories in food. When we consume one meal shortly after another then good compensation occurs when the size of the first meal controls the size of the second meal (i.e., a larger first meal causes people to consume a smaller second meal). In animals, poor compensation has been linked to a degraded 'cephalic-phase response.' This anticipatory response governs appetite and represents a series of physiological changes (e.g., salivation and insulin release) that prepare the body for the consumption and digestion of food. Critically, merely looking at or smelling a food is sufficient to elicit a response that is proportional to the calories contained in a food. This shows that learning is involved and that responses are based on previous encounters with individual foods. In this phase we will determine whether the cephalic-phase response is reduced in highly variable foods and whether this promotes poor compensation leading to overconsumption. Cephalic-phase responses will be measured in a number of ways. In particular, we will develop a new method based on changes in skin temperature near to the liver. Previously, researchers have found that this 'thermogenic response' is particularly sensitive to different foods. In this interdisciplinary project we will work with an expert in sensor technology to develop this sensitivity still further. In PHASE 2 we will explore the idea that variability in our food environment makes it more difficult for us to predict the extent to which a particular food will stave off hunger. In 2002 a Nobel Prize was awarded for advances in the field of behavioural economics. This work shows that uncertainty tends to generate cautious and conservative responses and has been used extensively to predict animal behaviour and a range of decisions relating to gambling, financial trading, and risk taking. We find it surprising that 'prospect theory' has not been applied to understand dietary behaviour in humans. For the first time, we will draw on these principles to test the idea that our variable food environment causes uncertainty about the effects of consuming a food, which creates confusion and a concern that hunger might be experienced after it has been consumed. In response to this uncertainty we make conservative dietary decisions and select and then consume larger portions of food. In summary, this project will address important questions relating to variability in our dietary environment. Previously, this issue has been largely overlooked. Nevertheless, research in animals would suggest that variability has the potential to play an important role in promoting overeating and obesity. The beneficiaries of this project are wide ranging. For individual consumers, this might involve increased public awareness of the effects of variable foods. For children, guidelines and/or legislation might be introduced to limit exposure to highly variable foods. For obese individuals, interventions might be possible that re-train sensitivity to the calories contained in specific foods. As such, this work has considerable potential to impact a number of groups, including; health professionals, policy makers, educators, and the wider public.

Over time, the orosensory properties of a food can serve as a cue (conditioned stimulus) that enables an individual to predict the caloric consequences of consuming a particular food. When these 'flavour-nutrient associations' are disrupted this promotes imprecise caloric regulation and weight gain in rats. In the UK, foods are now highly processed and their energy density is manipulated routinely. This increases exposure to inconsistent flavour-nutrient pairings. For the first time, this project will elucidate the effects of these inconsistent parings in humans. Specifically, it will explore two hypotheses. In Phase 1 we will test the hypothesis that inconsistent flavour-nutrient pairings disrupt learned cephalic-phase responses to food and that this compromises the ability to compensate for calories in food from meal to meal. As part of this research we will draw on expertise in 'sensing technology' to refine methods for measuring thermogenic responses to food. In Phase 2 we will test the hypothesis that inconsistent flavour-nutrient pairings have a direct effect on meal size, specifically, that they create 'uncertainty' (psychological) about the satiety that a food is expected to confer, and that this promotes the selection of larger meals. Despite its otherwise widespread application, this is the first time that 'prospect theory' will be used to make predictions about human dietary behaviour. In total, 11 studies will be conducted. Nine of these will be controlled laboratory experiments involving participants drawn from local staff and student populations. Four of these will use a 'preload' paradigm and two will establish causality by manipulating flavour-nutrient consistency directly. Two online studies will be conducted using custom software, written in Java script. This research will identify specific ways in which our modern food environment promotes obesity in the UK. As such, it will impact academics, the food industry, and the general public.

In response to the question 'Who are the beneficiaries of this research?' we have inserted five subheadings below. Under each subheading we have added text that identifies 'How will user groups benefit from this research?' 1. FOOD COMPANIES Multi-national food companies have long recognised that a competitive advantage can be gained by developing foods that confer health benefits. In particular, several companies (e.g., Unilever and Nestlé) develop and produce products that are specifically designed to aid weight loss by promoting satiety. This project will be of considerable benefit to these users because it will offer a methodology to evaluate their variability and the extent to which this impacts on the satiety that they confer. To this end, our measure of the thermogenic response has the potential to offer a highly informative, sensitive, and non-invasive assessment of the cephalic-phase response. To the applicants' knowledge, in the context of food variability, this has not been considered previously, in either an academic or an industry context. 2. HEALTH PROFESSIONALS/CLINICIANS If we are successful in establishing a relationship between food variability and overconsumption then this will offer an opportunity for health professionals and clinicians to develop appropriate intervention techniques that retrain sensitivity to the caloric content of foods in obese individuals. 3. POLICY MAKERS Research of this kind will assist policy makers because it has the potential to reveal a hitherto unknown relationship between our food environment and energy intake. In particular, this research will help to inform guidelines around healthy eating in adults. In children, it might also generate debate relating to whether children should be exposed to a variable food environment during their formative years. 4. NHS AND SOCIAL SERVICES The cost of obesity to the NHS and social services is considerable and it is expected to rise well above inflation over the next few decades. Not all countries have the same problem, and this is the case even after controlling for GDP. Therefore, it is important to carry out basic research that identifies ways in which specific aspects of our food environment contribute to overconsumption. If this can be achieved then changes to our food environment may be possible, offering an opportunity to implement cheap and effective solutions that reduce the burden of obesity on the NHS and related social services. 5. WIDER PUBLIC In addition to the above, the wider public will benefit from an opportunity to take individual and more informed control of the foods that they consume and the foods that they give their children.