Effect of sugar sweetened beverages on glycaemic control during prolonged sitting periods in sedentary overweight and obese adults

We will assess the impact of Sugar Sweetened Beverages (SSB) on glycaemic control in 29 sedentary, overweight/ obese participants. Each participant will complete two experimental conditions in a randomised, cross-over design at the Baker IDI clinical research suite, Level 4 of the Alfred Centre following a screening and familiarisation visit. The two interventions will be separated by a minimum 21-day wash-out period and will consist of: (i) 7 hours of uninterrupted sitting together with the consumption of water 90 minutes after a standardised breakfast and lunch meal and (ii) 7 hours of uninterrupted sitting together with the consumption of a SSB 90 minutes after a standardised breakfast and lunch meal. Glycaemic control will be measured directly through blood samples and the use of a continuous glucose monitor (CGM) worn for a 22 hour period from the morning of each trial condition until the following morning. Resting blood pressure will be taken every 60 minutes throughout both interventions using an automated blood pressure monitor. Endothelial function will be recorded at baseline (0 time), 3 hours (just prior to lunch) and at 6 hours (just after the final blood sample). Each participant will rest in a comfortable lounge chair and have access to a television with a DVD player and reading materials such as newspapers and magazines. Participants will be instructed to minimise excessive movement but will be allowed to visit the toilet when necessary. On each testing day, participants will be given a standardised breakfast and lunch meal according to their body mass and height. At -60min a baseline blood sample will be collected and blood pressure and heart rate recorded. After 1-hour of “steady-state”, another baseline blood sample, blood pressure and heart rate measurement will be recorded. A breakfast meal will be provided, commencing the experimental condition thereafter. Lunch will be provided 3 hours after the breakfast meal. Ninety minutes after each meal, (breakfast and lunch) participants will be instructed to consume the SSB or water. Participant will be instructed to drink the same volume of SSB or water within a 10-minute period. The two SSBs consumed (volume of each can- 375mL) after both the breakfast and lunch meals will constitute a total of 728kJ (174 calories) which consists of 42g of sugar (per serve). To employ a pragmatic approach and assimilate a typical western dietary composition the ’real world’ breakfast and lunch meals will comprise 33% of estimated energy requirements with a macronutrient profile of 53-55% energy from carbohydrate, 12-15% energy from protein and 30-33% energy from fat. Diet will be recorded 24 hours prior to each experimental visit. Participants will be instructed to refrain from engaging in structured moderate-to-vigorous intensity exercise in the 48 hours before each experimental day. To assess compliance and habitual physical activity, participants will be fitted with two objective activity monitors – an accelerometer (Actigraph model GT3X+) worn on the hip and an inclinometer (activPAL3TM) worn on the thigh for 7 days preceding each experimental condition. Sleep and activities will be recorded for 7 days prior to experimental visit.