Effects of exercise timing throughout a day of prolonged sitting on blood glucose regulation

INTERVENTION: This is a randomised, two‐condition crossover trial where participants will undergo 2x 48 h experimental conditions. Each condition will be separated by a minimum 7‐day washout period For both conditions participants will attend the laboratory at 5 pm on the evening prior to the main experimental trial day (day one) for fitting of a continuous glucose monitoring system and receive a standardised take‐home meal for dinner. Participants will also be fitted with an an accelerometer and an inclinometer for measurement of physical activity levels prior and during each experimental condition. Food and activity diaries will also be completed by participants prior to either experimental condition. On the main experimental trial day (day two) participants will arrive at the laboratory via taxi at 0730 h. A catheter will be inserted in the antecubital vein of the non‐dominant arm at 0800 h and remain in place until 1900 h. Participants will remain seated for the duration of the visit and blood samples will be collected at regular intervals. Identical meals will be provided at 0900 h, 1300 h and 1700 h. . Each meal will contain 33% total energy intake for the day with a macronutrient profile of 50% from carbohydrates, 30% from fat and 20% from protein. Additionally, participants will perform 30 minutes of aerobic exercise at 65% VO2max on a cycle ergometer. The timing of the exercise bout will depend on the experimental condition being undertaken. At 1900 h participants will return home via taxi and fast overnight. Condition A: Exercise will be performed at 0800 h, prior to breakfast. Condition B: Exercise will be performed at 1600 h, prior to dinner. Participants will then return to the lab for a follow up (day three) at 0730 and remain seated for the duration of the visit. A catheter will be inserted in the antecubital vein of the non‐dominant arm at 0800 h and remain until 1600 h for serial blood sampling. Participants will be provided identical meals to day two at 0900 h and 1300 h. At 1630 h all monitoring devices will be removed. CONDITION: Obesity Type 2 diabetes PRIMARY OUTCOME: Blood glucose area under the curve (using continuous glucose monitoring systems) SECONDARY OUTCOME: Appetite scores for hunger and satiety measured using a visual analogue scale on a laptop (composite outcome) Plasma insulin area under the curve Plasma triglyceride area under the curve INCLUSION CRITERIA: Sedentary overweight or obese [body mass index (BMI) > 25 kg/m2 but < 45 kg/m2] adults with a familial history of type 2 diabetes (diagnosis in a first or second degree relative).