Eating a high fibre diet has been shown in numerous studies to benefit the health, particularly with regard blood sugar control and normal weight maintenance. Soluble dietary fibre has specific gel-forming properties that can slow nutrient absorption and delay gastric emptying, and these properties may be particularly beneficial at increasing satiety and decreasing the glycaemic effect of food. In addition, fibre can be metabolised by gut bacteria to form short-chain fatty acids that can subsequently be absorbed and used as a source of energy in human metabolism. A review article has suggested that the energy intake of meals is inversely associated with the fibre content and its viscosity. Barley grain contains a soluble fibre called β-glucan that has been shown to improve blood lipids and decrease the glycaemic index of food, which suggests that it may have satiety effects similar to other fibres.
Because of the possibility that β-glucan may have beneficial metabolic properties, researchers1 have investigated the effects of a specially developed barley biscuit containing 5.2% β-glucan on food intake and appetite in 290 healthy adolescents. Subjects were fed a barley biscuit snack containing either 150 or 450 kcal, or a control biscuit with a similar energy content that did not contain β-glucan. The low calories barley biscuit produced a significant increase in satiety when compared to the low calorie control biscuit, with satiety peaking 15 min post-consumption, before returning to baseline. At a subsequent lunch meal, energy consumption was ≈22% lower following the barley biscuit, but only in females. In males and females, the energy consumption at the subsequent lunch correlated with the calorific value of the biscuit, but not with the type of biscuit. There was no change in the composition of food eaten at subsequent meals under any condition.
The total fibre content of the biscuit in this study was 12.6g, of which 5.2g was β-glucan. However, the control biscuits were made from 100% wheat floor with a low fibre content and it is therefore difficult to draw conclusions about the effects of β-glucan specifically, in the absence of a high fibre control. It is also difficult to draw concussions from the data, because the energy supplied by fibre requires fermentation in the colon to produce short-chain fatty acids. This process may contribute to the satiety effects seen with fibre, and the process is known to continue for many hours post-consumption. The short duration of this study therefore did not allow adequate time for some of the metabolic changes caused by fibre to occur. However, at the lower energy intake, fibre content did significantly decrease hunger ratings, supporting previous studies that show beneficial effects for fibre on appetite.
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