Glycerol is a sugar alcohol that is used for the synthesis of triglycerides by all life. In animal studies glycerol administered intraperitoneally or subcutaneously induces hypophagia, and oral administration leads to a transient decrease in the animals body weight. The reason for this is not clear, but glycerol may act as a feedback signal to the hypothalamus regarding the extent of the mobilisation of adipose tissue stores. As lipolysis proceeds, plasma levels of glycerol rise on account of the catabolism of triglycerides from adipose tissue. Plasma glycerol levels therefore rise during periods of extensive triglyceride catabolism as might occur during fasting, starvation or exercise, and this may play some part in the appetite suppression associated with these physiological conditions. Although the mechanisms are not fully understood, in animals at least glycerol may cause a reduction in energy intake through an unknown mechanism and this may cause a temporary reduction in body weight.
Glycerol has also been tested on humans subjects for it hypophagic effects. In one study1, investigators fed 12 non-obese subjects either 7.5 grams of glycerol, an isocaloric amount of glucose or water 20 minutes before a meal. The subjects were then fed a palatable soup and their energy intakes were measured. The results of the study showed that administration of a preload of glycerol reduced the energy intake of the subsequent meal by around 10 %, when compared to both water and glucose preloads (433 kcal versus 479 kcal versus 479 kcal for glycerol and water and glucose, respectively). In those subjects consuming the glycerol preload the plasma glycerol concentrations 20 minutes after the soup was around 10 times higher than baseline readings. There were no differences in the free fatty acid concentrations for any of the treatments. Subjective ratings for hunger did not differ between the subjects either before or after administration of the treatments.
Dr Robert Barrington’s Nutritional Comments: A number of other studies have investigated the ability of glycerol to cause appetite suppression. Taken as a whole, there appears to be no overall consensus in the literature regarding any beneficial effect. The fact that glycerol is able to cause hypophagia and weight loss in animals does tend to suggest that the effects are real however. Until more is understood about the mechanisms of action it is difficult to say whether glycerol could be a beneficial weight loss supplement. Therefore the best way to suppress the appetite still remains the consumption of high quality nutrient dense foods eaten in an ad libitum fashion.
RdB
