This study will investigate the effect of dietary macronutrient manipulation on glycogen (stored carbohydrate) levels in the muscle and substrate oxidation during exercise. The investigators will investigate the hypothesis that manipulating the macronutrient content of the diet will alter the levels of glycogen in the muscle and, in turn, substrate oxidation during exercise.

One way to help reduce body fat is to expend more energy from the oxidation of fat as a fuel. Exercise is one way to increase fat oxidation. The extent to which exercise facilitates the use of fat as a fuel may be influenced by an individual's dietary intake.

This study aims to establish the effect of dietary macronutrient manipulation on muscle glycogen levels and substrate oxidation during exercise. Participants will undertake three separate trial periods. During each trial period participants will consume a diet containing different macronutrient compositions. For each of the trials the investigators will assess how the macronutrient composition of the diet affects muscle glycogen level and substrate oxidation during exercise.

Inclusion Criteria:

• Good general health
• Non-smoking - currently and for the past 5 years
• Fitness - V̇O2max 40-60 ml/kg/min
• Body mass index (20-25 kg/m2)

Exclusion Criteria:

• Known or suspected intolerance to the dietary interventions or their stated ingredients.
• Participation in another clinical study or receipt of an investigational drug within 30 days of the screening visit.
• Previous participation in this study.
• Recent history (within the last year) of alcohol or other substance abuse.
• An employee of the sponsor or the study site or members of their immediate family.
• Abnormal / extreme habitual dietary practice / intake
• Recent (≤3 months) dietary practice that may be deemed as low and/or high in macronutrients will be excluded.
• The taking of any prescribed medication