The replacement in the diet of refined carbohydrate and fat with fibre and protein has been shown to promote satiety and improve glucose and insulin profiles. It is less clear whether the macronutrient composition of individual foods such as snacks have any meaningful impact on metabolic parameters and satiety. We examined if the consumption of higher protein higher fibre snack bars would result in reducing outcome measures such as food intake and glucose and insulin patterns compared to a conventional isocaloric high fat high refined carbohydrate snack bar. Twenty three women were randomized in a single blind cross over study with 2 interventions, a high fat high sugar snack bar and a comparatively higher protein, higher fibre snack bar intervention. Snack bars were eaten at mid morning and mid afternoon, and a standard breakfast and ad libitum buffet lunch. The glucose and insulin responses over 9 hours were significantly lower (P = 0.014 and P = 0.012 respectively) during the high protein snack bar intervention. Peak glucose levels were also 16% lower after the morning HP bar (P <0.001). The morning high protein bar reduced the energy intake at the buffet lunch meal by 5% (4657 +/- 1025KJ vs 4901 +/- 1186KJ, P < 0.05). Altering the macronutrient composition of a snack bar can assist in reducing the energy intake at a subsequent meal and improve short term glucose and insulin profiles.