Mind over matter may really work when it comes to managing appetite. Researchers at the University of Birmingham, U.K. have found that recalling foods eaten at lunch has an inhibitory effect on subsequent snacking later the same day. The study is currently in press and will be published in the journal Physiology & Behavior . The effect was observed regardless of the type of snack eaten or palatability. The study also found that meal recall was only effective in decreasing the amount eaten if participants did not have a tendency to overeat.
photo credit: Perfecto Insecto
The study conclusions are based on the results of three experiments described below. Participant eating behavior was determined in these experiments using a questionnaire that included scales assessing dietary restraint (meaning the conscious determination and effort to restrict food intake and calories to control body weight) and tendency toward dietary disinhibition (meaning the tendency to overeat in certain situations). The studies evaluated the inhibitory effects of lunch recall and were conducted to examine the influence of (1) snack palatability, (2) individual dietary traits and (3) the time elapsed since lunch.
Experiment 1: Recall of today’s lunch and subsequent intake of popcorn
The first experiment investigated whether recall of the last meal decreased intake of popcorn differing in added salt and participant-rated pleasantness. Participants took part in one of two experimental conditions:
- The Lunch Today condition, in which participants were asked to recall what they had eaten for lunch that day immediately before tasting and rating the afternoon snack.
- The Lunch Yesterday condition, in which participants were asked to recall what they had eaten for lunch the previous day immediately before tasting and rating the afternoon snack.
Participants (14 young healthy male students) were tested between 2:30 and 4:30 in the afternoon. Upon arrival, those in the Lunch Today condition were asked to write down in ask much detail as possible what they ate for lunch that day. Participants in the Lunch Yesterday condition were asked to do the same for lunch the previous day. Following an assessment of hunger, fullness, desire to eat and mood, participants completed a popcorn taste test. Three large bowls of popcorn were offered with varying amounts of salt (no salt, low salt and high salt) to provide a scale of palatability. After tasting and rating each of the popcorn types, participants were told they could help themselves to any popcorn left over.
The researchers found that when participants were asked to recall lunch eaten earlier that day, intake of all three popcorn types (measured by weighing the bowls of popcorn consumed by each participant before and after each test) was reduced compared to when participants were asked to recall lunch eaten the previous day.
Experiment 2: Recall of today’s lunch and subsequent snack intake: effects of dietary restraint and disinhibition
The second experiment investigated whether the effect of meal recall on snacking is dependent on the tendency towards disinhibition, specifically the tendencies to consciously restrict food intake and to overeat when tempting food is present or other people are eating. Participants (75 young healthy female students) were separated into four groups based on dietary restraint and tendency toward disinhibition:
- Low restraint/Low disinhibition
- High restraint/Low disinhibition
- Low restraint/High disinhibition
- High restraint/High disinhibition
Two participants were excluded because they reported having diabetes or food allergies, were smokers or had a body mass index (BMI) outside the normal range.
Participants again took part in two experimental conditions, the Lunch Today or Lunch Yesterday condition. However, prior to the main test, they attended an introductory session to taste and rate the popcorn, providing the researchers with a baseline measurement of snack intake for each of the four groups. Participants ate their lunch at least 2 hours prior to the test session.
The researchers found no evidence that dietary restraint affected the response to meal recall. However, only participants scoring low in the tendency toward disinhibition decreased their snack intake after recalling lunch. Participants scoring high actually ate as much or more of all three popcorn types! The researchers hypothesized that participants with a tendency towards disinhibition (overeating) may have impairments in working memory related to preoccupying thoughts of food and body shape, as has been shown previously . These impairments would thus interfere with memory encoding or retrieval of the recent meal.
Experiment 3: Recall of today’s lunch and subsequent snack intake: effect of time elapsed since the lunch
The aim of Experiment 3 was to test the hypothesis that the effect of meal recall on snack intake is dependent on memory. Introduction of a delay between a prior event and a later task is typical in memory testing. Thus, researchers examined whether the effect of meal recall is time dependent. Researchers again excluded participants if they reported having diabetes or food allergies, were smokers, had a body mass index (BMI) outside the normal range, or were not habitual breakfast eaters (to control for food intake prior to the controlled lunch). The sample comprised 47 healthy young female students who were asked to remember either their lunch eaten earlier that day or their trip to the test session. Instead of popcorn, the effect of meal recall on cookie intake was measured after a short delay (1-hour post lunch) or a longer delay (3-hour post lunch).
Based on the results of Experiment 2, researchers also assessed whether the effect of meal recall is moderated by dietary traits. Prior to the main test, participants attended an introductory session to taste and rate the cookies that would be eaten in the main experiment, providing the researchers with a baseline measurement of snack intake.
Participants were divided into two groups: half were asked to recall the lunch they had eaten earlier that day (Lunch Today condition) and half were asked to recall their journey to the University campus (Journey Control condition). Within each group, participants attended two test days, each comprising two sessions: a lunch session, which took place between 12:00 and 1:30 p.m., and a snack tasting session, which took place either 1 hour or 3 hours after lunch. Approximately half the participants completed the 1-hour post lunch test followed by the 3-hour post lunch test and the remaining participants experienced the tests in the reverse order.
Replicating the results of Experiment 2, researchers again found an effect of lunch recall on snacking for participants that scored low in tendency toward disinhibition. They also found that the effect of snack intake was time dependent, with participants significantly decreasing their snack intake after recalling lunch in the 3-hour delay condition, but not the 1-hour delay condition. According to the lead author of the study, Psychologist Dr. Suzanne Higgs :
The women who had been asked to recall their lunches and who took the taste test after three hours showed significantly reduced appetites compared to those who had detailed their journeys. This may be because after just one hour, the memory of eating lunch was still vivid enough to affect all the women’s appetites.
Taken together, the results of these experiments show that recall of a recent meal before eating a snack can decrease the amount of snack eaten. The results also suggest that this effect is likely to be related to memory of the meal. The effect of recent meal recall is delay-dependent; snacking was reduced when testing took place 3-hours post lunch and not after 1-hour post lunch. While these results identify the phenomenon, they don’t address how recollection of a recent meal affects subsequent intake. The authors speculate that changes in participants “feeling full” are cognitively mediated and are dependent on a number of factors, including food-related sensory cues, current internal state cues, how participents “felt” after the recent meal, and how they anticipate “feeling” following a snack.
As paradoxical as it sounds, these results suggest that by concentrating on a recent meal, you can reduce your desire to snack. If you’re up to the challenge, give it a try and let me know how you do!
Higgs et al. Recall of recent lunch and its effect on subsequent snack intake. Physiol Behav. 2008 Mar 4 [Epub ahead of print].
Kemps and Tiggemann. Working memory performance and preoccupying thoughts in female dieters: evidence for a selective central executive impairment. Br J Clin Psychol. 2005 Sep;44(Pt 3):357-66.
- Focus on Food — Thinking About Your Last Meal Could Reduce Snacking. University of Birmingham News and Events. 2008 Apr 24.