Suzanne Higgs

Television watching during lunch increases afternoon snack intake of young women.

Eating while watching television has been shown to increase food intake in part due to the distracting effects of television viewing. It is also known that enhancing memory for the specific attributes of foods eaten in the recent past decreases subsequent food intake. Because distraction at the time of encoding interferes with memory formation, we predicted that television watching during lunch would increase afternoon snack intake due to impaired memory for recent eating. Using a repeated-measures design, 16 young women undergraduate students visited the laboratory to eat a fixed lunch either while watching television or in the absence of television. Intake of cookies at a tasting session later that afternoon was measured and participants recalled eating the lunch and rated the memory for vividness. All participants ate all of the lunch and rated appetite during lunch did not differ according to condition. Participants ate significantly more cookies after they had eaten their lunch while watching television than when they had eaten their lunch while not watching television and this effect could not be attributed to an effect of television watching on rated mood or appetite before the snack session. Watching television while eating lunch was also associated with reduced vividness ratings of the memory of the lunch. These results suggest that the effects of television watching on food intake extend beyond the time of television watching to affect subsequent consumption. They further suggest that this effect may be related to an effect of television watching on encoding of the memory of the meal.

Does low-energy sweetener consumption affect energy intake and body weight? A systematic review, including meta- analyses, of the evidence from human and animal studies

By reducing energy density, low-energy sweeteners (LES) might be expected to reduce energy intake (EI) and body weight (BW). To assess the totality of the evidence testing the null hypothesis that LES exposure (versus sugars or unsweetened alternatives) has no effect on EI or BW, we conducted a systematic review of relevant studies in animals and humans consuming LES with ad libitum access to food energy. In 62 of 90 animal studies exposure to LES did not affect or decreased BW. Of 28 reporting increased BW, 19 compared LES with glucose exposure using a specific ‘learning’ paradigm. Twelve prospective cohort studies in humans reported inconsistent associations between LES use and body mass index (−0.002 kg m−2 per year, 95% confidence interval (CI) −0.009 to 0.005). Meta-analysis of short-term randomized controlled trials (129 comparisons) showed reduced total EI for LES versus sugar-sweetened food or beverage consumption before an ad libitum meal (−94 kcal, 95% CI −122 to −66), with no difference versus water (−2 kcal, 95% CI −30 to 26). This was consistent with EI results from sustained intervention randomized controlled trials (10 comparisons). Meta-analysis of sustained intervention randomized controlled trials (4 weeks to 40 months) showed that consumption of LES versus sugar led to relatively reduced BW (nine comparisons; −1.35 kg, 95% CI –2.28 to −0.42), and a similar relative reduction in BW versus water (three comparisons; −1.24 kg, 95% CI –2.22 to −0.26). Most animal studies did not mimic LES consumption by humans, and reverse causation may influence the results of prospective cohort studies. The preponderance of evidence from all human randomized controlled trials indicates that LES do not increase EI or BW, whether compared with caloric or non-caloric (for example, water) control conditions. Overall, the balance of evidence indicates that use of LES in place of sugar, in children and adults, leads to reduced EI and BW, and possibly also when compared with water.

Cognitive influences on food intake: The effects of manipulating memory for recent eating

Recent evidence suggests that enhancing memory of the last meal decreases later snack intake, whereas disruption of encoding in memory of the last meal increases subsequent snack intake. Other studies have found that manipulating cognitions at the time of eating, such as beliefs about the timing and composition of meals, can affect subsequent intake. The effects of many of these cognitions are likely to depend on prior association in memory between situational and sensory cues and particular postingestional or affective consequences of eating. Hence, memory for the specific attributes of foods eaten in the recent past, and memory for the predicted consequences of eating acquired over repeated experiences are important influences on food intake. These data are consistent with evidence of hyperphagia in amnesic patients and laboratory animals with lesions to the hippocampus, an important substrate for learning and memory.

Postprandial Administration of Intranasal Insulin Intensifies Satiety and Reduces Intake of Palatable Snacks in Women

The role of brain insulin signaling in the control of food intake in humans has not been thoroughly defined. We hypothesized that the hormone contributes to the postprandial regulation of appetite for palatable food, and assessed the effects on appetite and snack intake of postprandial versus fasted intranasal insulin administration to the brain in healthy women. Two groups of subjects were intranasally administered 160 IU insulin or vehicle after lunch. Two hours later, consumption of cookies of varying palatability was measured under the pretext of a taste test. In a control study, the effects of intranasal insulin administered to fasted female subjects were assessed. Compared with placebo, insulin administration in the postprandial but not in the fasted state decreased appetite as well as intake and rated palatability of chocolate chip cookies (the most palatable snack offered). In both experiments, intranasal insulin induced a slight decrease in plasma glucose but did not affect serum insulin concentrations. Data indicate that brain insulin acts as a relevant satiety signal during the postprandial period, in particular reducing the intake of highly palatable food, and impacts peripheral glucose homeostasis. Postprandial intranasal insulin administration might be useful in curtailing overconsumption of snacks with accentuated rewarding value.

Social norms and their influence on eating behaviours

Social norms are implicit codes of conduct that provide a guide to appropriate action. There is ample evidence that social norms about eating have a powerful effect on both food choice and amounts consumed. This review explores the reasons why people follow social eating norms and the factors that moderate norm following. It is proposed that eating norms are followed because they provide information about safe foods and facilitate food sharing. Norms are a powerful influence on behaviour because following (or not following) norms is associated with social judgements. Norm following is more likely when there is uncertainty about what constitutes correct behaviour and when there is greater shared identity with the norm referent group. Social norms may affect food choice and intake by altering self-perceptions and/or by altering the sensory/hedonic evaluation of foods. The same neural systems that mediate the rewarding effects of food itself are likely to reinforce the following of eating norms.

Memory and its role in appetite regulation

The importance of memory processes for the formation and expression of conditioned food preferences and satieties has long been appreciated. Recently, based on the eating of multiple meals in amnesic patients, it has been suggested that information about a recent eating episode may be factored into decisions about how much to consume at the next meal. In support of this, it has been shown that enhancing memory for a recent meal, by cueing neurologically intact participants to recall items eaten at lunch, suppresses intake at a taste test later in the afternoon. This effect is specific to recalling food eaten that day, since asking participants to think about lunch consumed the previous day had no effect on intake. These studies suggest that memory for recent eating has a role to play in controlling everyday eating. However, the involvement of memory and cognition does not exclude learnt control by physiological after effects of the recent meal; indeed, this seems likely from the known functions of the hippocampal system that is damaged in amnesic patients.

Prompting Healthier Eating: Testing the Use of Health and Social Norm Based Messages

OBJECTIVE Health based messages are commonly used to promote fruit and vegetable intake, but are limited in their effectiveness. Social norm messages, which suggest other people are eating healthily, may be more effective. Our aim was to compare the effect on food selection of a message containing health related information about fruit and vegetable consumption with a message containing social normative information about consumption of fruit and vegetables. METHOD In two laboratory studies, predominantly young female adult students were exposed to a health or social norm message about fruit and vegetables. In Study 1, lunch meal food selections and intake were assessed and in Study 2, snack food selections and intake were assessed. Study 1 examined the effect of a descriptive social norm (information about what others are eating) versus a health message and Study 2 examined the effect of both a descriptive norm and an injunctive norm message (information about what others approve of) versus a health message. RESULTS In Study 1, exposure to a descriptive social norm message resulted in significantly more vegetables being selected and eaten than exposure to a health message. In Study 2, exposure to a descriptive social norm message resulted in significantly more fruit and vegetables and less high energy dense snack food being selected and eaten than exposure to a health message. There was no effect of exposure to the injunctive norm message. In both studies, significant differences between the social norm and health message conditions were observed in low but not high usual consumers of fruit and vegetables. CONCLUSIONS For the promotion of healthy eating, social norm messages may be more effective than health messages for consumers failing to adhere to dietary guidelines.

Sensory-Specific Satiety Is Intact in Amnesics Who Eat Multiple Meals

What is the relationship between memory and appetite? We explored this question by examining preferences for recently consumed food in patients with amnesia. Although the patients were unable to remember having eaten, and were inclined to eat multiple meals, we found that sensory-specific satiety was intact in these patients. The data suggest that sensory-specific satiety can occur in the absence of explicit memory for having eaten and that impaired sensory-specific satiety does not underlie the phenomenon of multiple-meal eating in amnesia. Overeating in amnesia may be due to disruption of learned control by physiological aftereffects of a recent meal or to problems utilizing internal cues relating to nutritional state.

Focusing on food during lunch enhances lunch memory and decreases later snack intake.

We investigated whether eating lunch mindfully, in contrast to eating with distractions or no particular focus, reduces later snack intake and if this is related to a measure of meal memory. The design was between-subjects with three conditions. Twenty-nine female undergraduate students either ate a fixed lunch while (1) focusing on the sensory characteristics of the food as they ate (food focus group), (2) reading a newspaper article about food (food thoughts control group) or (3) in the absence of any secondary task (neutral control group). Cookie intake later that afternoon was measured as well as rated vividness of memory of the lunch. Participants ate significantly fewer cookies in the food focus group than in both the food thoughts control group or the neutral control group. Rated appetite before the snack session was lower in the food focus group than in the other two groups and rated vividness of lunch memory was higher. Rated vividness of lunch memory was negatively correlated with snack intake. These results suggest that enhancing meal memory by paying attention to food while eating can reduce later intake and are consistent with the suggestion that memory plays an important role in appetite control.

Susceptibility to weight gain. Eating behaviour traits and physical activity as predictors of weight gain during the first year of university.

The transition to University has been identified as a possible period for weight gain but few studies have addressed the extent of this experience in UK Universities. The present study was conducted in four Universities in England and Scotland to directly measure changes in body weight, waist circumference and body composition in students during their first year. Two hundred and fifty first-year students completed psychometric eating behaviour questionnaires and a validated physical activity survey before attending one of the laboratories for standardised assessments of height, body weight, waist circumference and body composition at 0, 3, and 12-months. Significant but small and transitory increases in all weight outcomes (e.g. body weight=0.83±2.1 kg) were observed except for fat-free mass. Weight-related measures at baseline predicted changes in weight over 12-months but not 3-months. Disinhibition, power of food and binge eating were associated with change in fat mass while physical activity, cognitive restraint and sensitivity to reward were associated with change in fat-free mass. Weight gain occurs in the first year of University in the UK, but appears to be small and transitory. Changes in fat mass were related to opportunistic eating and the tendency to overconsume, while change in fat-free mass related to physical activity and low dietary restraint in conjunction with drive to experience reward. Psychological markers underlying changes in body composition can inform strategies to promote self-regulation in young adults during a critical life period for weight gain.