An exploration of lipids with the potential to influence appetite and food intake
Dietary fat is considered the least satiating of the macronutrients. Coupled with its high palatability, fat has been implicated in the growth of obesity. Despite this, there are lipids which exert greater satiety than others. This thesis has explored further various lipids which may exert these effects. A literature review identifying lipids which have the potential to beneficially affect appetite, followed by a systematic review and meta-analysis on medium-chain triglycerides (MCT) was conducted. A series of three experiments followed: 1) a comparison of the satiety response to MCT and conjugated linoleic acid in individuals with healthy weight or overweight and obesity, 2) the combination of MCT and cycling exercise on energy balance, and 3) an investigation into the relationship between MCT and the physical form in which they are consumed, and the effect on satiety. To achieve this, 70 individuals (M: 42, F: 28; mean ± SD: age 27 ± 8 years, body mass index [BMI] 24.5 ± 8.0 kg·m-2) were recruited into three experiments. The results of these reviews and experiments highlight that there are various lipids which may be useful in weight management strategies, although research is limited. MCT do decrease energy intake compared to long-chain triglycerides (LCT) irrespective of weight status. This effect is not mediated by gut peptide hormones measured in this thesis but appears to be related to a delay of gastric emptying, and potentially an increase in ketone body production. These effects are only observed in resting conditions, whereas consuming them alongside exercise poses no additional benefit. Consuming MCT in a resting state does, however, increase resting metabolic rate through dietary induced thermogenesis. Discrepancies in the extant literature can be explained via the form in which MCT are delivered, as MCT in solid form is no more satiating than LCT in solid form, where MCT in liquid form is.
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