Assessing "chaotic eating" using self-report and the UK Adult National Diet and Nutrition Survey: No association between BMI and variability in meal or snack timings.

Although regular meal timings are recommended for weight loss, no study has characterised irregularity in the timing of eating occasions or investigated associations with body-mass index (BMI). Here, we characterise "chaotic eating" as the tendency to eat at variable times of day. In two studies, we used a novel measure to explore the relationship between BMI and chaotic eating. In Study 1 (N = 98) we measured BMI and used a self-report measure to assess the usual range of times that meals and snacks are consumed over a seven-day period, as well as meal and snack frequency. A separate meal and snack 'chaotic eating index' was derived from the number of possible thirty-minute snack- or meal-slots, divided by the frequency of these eating events. After adjusting for age, gender, and dietary habits (Three-Factor Eating Questionnaire) we found no relationship between BMI and chaotic eating of meals (ß = -0.07, p = 0.73) or snacks (ß = -0.10, p = 0.75). In Study 2, we calculated the same chaotic eating index (meals and snacks) using data from the UK National Diet and Nutrition Survey of adults 2000-2001 (seven-day diet diaries; N = 1175). Again, we found little evidence that BMI is associated with chaotic eating of meals (ß = 0.16, p = 0.27) or snacks (ß = 0.15, p = 0.12). Together, these results suggest that irregular eating timings do not promote weight gain and they challenge guidelines that recommend regularity in meal timings for weight loss.

"What time is my next meal?" delay-discounting individuals choose smaller portions under conditions of uncertainty.

'Dietary' delay discounting is typically framed as a trade-off between immediate rewards and long-term health concerns. Our contention is that prospective thinking also occurs over shorter periods, and is engaged to select portion sizes based on the interval between meals (inter-meal interval; IMI). We sought to assess the extent to which the length of an IMI influences portion-size selection. We predicted that delay discounters would show 'IMI insensitivity' (relative lack of concern about hunger or fullness between meals). In particular, we were interested in participants' sensitivity to an uncertain IMI. We hypothesized that when meal times were uncertain, delay discounters would be less responsive and select smaller portion sizes. Participants (N = 90) selected portion sizes for lunch. In different trials, they were told to expect dinner at 5pm, 9pm, and either 5pm or 9pm (uncertain IMI). Individual differences in future-orientation were measured using a monetary delay-discounting task. Participants chose larger portions when the IMI was longer (p < 0.001). When the IMI was uncertain, delay-discounting participants chose smaller portions than the average portion chosen in the certain IMIs (p < 0.05). Furthermore, monetary discounting mediated a relationship between BMI and smaller portion selection in uncertainty (p < 0.05). This is the first study to report an association between delay discounting and IMI insensitivity. We reason that delay discounters selected smaller portions because they were less sensitive to the uncertain IMI, and overlooked concerns about potential future hunger. These findings are important because they illustrate that differences in discounting are expressed in short-term portion-size decisions and suggest that IMI insensitivity increases when meal timings are uncertain. Further research is needed to confirm whether these findings generalise to other populations.