Rolls et al. [31] proved that a reduction in portion size of 25% of all foods on two consecutive days led to a reduced food intake of approximately 10%. In their study, however, participants (i.e. randomly recruited young women) were invited in a laboratory setting, where the portion sizes and energy density of the foods of daily menus were changed. From a scalability and public health point of view, it is clear that confirmation by real-life setting trials is needed. To our knowledge, only one US study reduced the portion size of a calorie-dense food product (i.e. French fries) served in an on-campus university restaurant, presented in plain paper bags [33]. This experiment showed that reducing the portion size of French fries by 50% resulted in a 30% decrease in French fries consumption per consumer as well as 31% reduction in plate waste per consumer [33]. In an intercept survey, 70% of the 322 questioned French fries consumers indicated they did not notice the change in portion size [33]. In the latter study, consumers consisted primarily of US freshmen while dietary intake, and thus also dietary compensational effects during the rest of the day were not assessed. So, from this study we cannot conclude that portion size reduction will lead to reduced food intake, as the 50% reduction in French fries consumption may have been compensated for later on the day. In the laboratory experiment by Rolls et al. [34], ratings of hunger decreased as the size of the package containing potato chips increased, but this did not lead to a reduced energy intake at the subsequent dinner later that day. Such possible adjustments were also checked in a study by Jeffery et al. [35], where unannounced 24-h dietary recalls were conducted by phone after a 50% reduction of pre-packaged lunches in a naturalistic setting. Results showed that mean 24-h energy intake decreased with 278 kcal/day when a small lunch was served in comparison with a large one [35]. A British study investigating the effects of reducing breakfast both on hunger feelings and subsequent energy intake, showed no influence on subsequent energy intake but did show a significance difference in hunger feeling after reducing the portion with 40%. However, this study was conducted in an overweight population in a laboratory setting [36].
Only students and employees visiting the on-campus restaurant during both the baseline and intervention week were eligible to be allocated to the experimental or control group. The experimental group was formed by students and employees choosing French fries along with the same main dish on the same day of both weeks. In contrast, the control group consisted of students and employees choosing the same side dish different from French fries along with the same main dish on the same day of both weeks. Students and employees who chose a different main or side dish during the intervention week compared to the control week were excluded.
Frenchfry: Experiment 062 download
During the fifth (i.e. post-intervention) week, all consumers of the experimental group were re-contacted by telephone. Consumers were asked whether or not they had noticed the reduced French fries portion size during the intervention week. If so, they were also asked to estimate the extent of alteration in portion size. Finally, participants were asked if the smaller portion was sufficient and whether or not a portion size reduction could be permanently implemented in the on-campus restaurant.
During the preparation phase of the experiment the difference between fried and deep-frozen French fries was measured in order to be able to calculate how many kilograms of fried French fries came out of the deep-frozen French fries. The weight of fried French fries was equal to approximately 73% of the weight of deep-frozen French fries. French fries were fried for 3 min in vegetable oil (Vandemoortele Risso Chef), consisting of palm oil, rapeseed oil, sunflower oil, and corn oil, at a temperature of 175 C. Total French fries consumption (in kg) was calculated by subtracting the total plate waste (in kg) from the total amount produced (i.e. kg of deep-fried French fries used multiplied by 73%). Consumption per consumer was calculated by dividing the total French fries consumption by the number of French fries consumers. A similar calculation was done to determine portion waste. By dividing total French fries consumed per portion by the amount produced per portion, the ratio of consumed French fries per portion was calculated. A similar calculation was done to determine the ratio of waste per portion.
MV, MS, PM, ED, BD, PC and TD conceived and designed the experiments. MV, TD and VV performed the experiments. MV and TD analysed the data. MV wrote the manuscript. VV, MS, PM, ED, BD, PC and TD reviewed the manuscript critically. All authors read and approved the final manuscript.
The suitability of hydrogenated soybean oils (fats) for prefrying of deep-frozen french fries has been investigated in a frying and storage experiment with five hydrogenated oils, of which four were commercially available and one was experimentally prepared. Three frying oils were hydrogenated soybean fats (0% C18:2 and C18:3), one was a partly hydrogenated soybean oil (25% C18:2; 0% C18:3) and one a hydrogenated palm fat (0% C18:2). An intermittent frying and heating procedure was used.
Experimental design (a) and the procedure of experimental sessions (b). Participants were enrolled in a randomized study consisting of 2 crossover experiments (food-picture and control experiments), and asked to watch a series of pictures for 5 min (visual stimulation session) and to close their eyes for 3 min before and after the picture presentation (eye-closed sessions). Pictures of food items were presented as visual stimuli during the food-picture experiment, and mosaic pictures of food items were presented as visual stimuli during the control experiment. The contents of pictures were not disclosed to the study participants in advance
TY and MT took part in planning and designing the experiment, collected the data, performed the data analyses and drafted the manuscript. AI took part in planning and designing the experiment, collected the data, and performed the data analyses. YY took part in performing data analyses and literature survey. YW took part in planning and designing the experiment and helped drafting the manuscript. All authors read and approved the final manuscript. 2ff7e9595c
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