Abstract
The vast majority of preload-test-meal studies that have investigated the effects on energy intake of disguised nutrient or other food/drink ingredient manipulations have used a cross-over design. We argue that this design may underestimate the effect of the manipulation due to carry-over effects. To test this we conducted comparable cross-over (n = 69) and parallel-groups (n = 48) studies testing the effects of sucrose versus low-calorie sweetener (sucralose) in a drink preload on test-meal energy intake. The parallel-groups study included a baseline day in which only the test meal was consumed. Energy intake in that meal was used to control for individual differences in energy intake in the analysis of the effects of sucrose versus sucralose on energy intake on the test day. Consistent with our prediction, the effect of consuming sucrose on subsequent energy intake was greater when measured in the parallel-groups study than in the cross-over study (respectively 64% versus 36% compensation for the 162 kcal difference in energy content of the sucrose and sucralose drinks). We also included a water comparison group in the parallel-groups study (n = 24) and found that test-meal energy intake did not differ significantly between the water and sucralose conditions. Together, these results confirm that consumption of sucrose in a drink reduces subsequent energy intake, but by less than the energy content of the drink, whilst drink sweetness does not increase food energy intake. Crucially, though, the studies demonstrate that study design affects estimated energy compensation.
Highlights
The preload-test-meal procedure has been used extensively to investigate the short-term effects of food and drink ingredients on energy intake
A good example of the latter is a large number of studies which have investigated the satiety effects of sugars in drinks and semi-solid foods, using lowcalorie sweeteners to control for sweetness in the reduced-sugar or sugar-free comparison preload
Cross-over designs risk underestimating the ‘true’ satiating effect of the manipulated ingredient. Due to this uncertainty about the estimation of satiety effects, and energy compensation, in preload-test-meal studies using cross-over designs, we conducted comparable parallelgroups and cross-over studies testing the effects of sucrose versus low-calorie sweetener in a drink preload on test-meal energy intake
Summary
The preload-test-meal procedure has been used extensively to investigate the short-term effects of food and drink ingredients on energy intake. In some studies sensory properties and/or information provided on the food or drink have been manipulated independently of nutrient content (e.g., McCrickerd, Chambers, & Yeomans, 2014) In other studies both nutrient content and visual and oro-sensory properties of the preload vary together (Almiron-Roig et al, 2013), but a common approach is to manipulate nutrient content while, as far as possible, matching the appearance, taste, flavour and texture of the different preloads. This tests the effects of the nutrient or other ingredient in question free from the influences of differential expectations and anticipatory responses. A good example of the latter is a large number of studies which have investigated the satiety effects of sugars in drinks and semi-solid foods, using lowcalorie sweeteners to control for sweetness in the reduced-sugar or sugar-free comparison preload
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