Standardised meals

For chapter 4A-C and chapter 5A-B patients consumed a total ~5.0 g.carbohydrate.kg-1BM over the course of each trial day. This was estimated to provide enough carbohydrate to cover the cost of the exercise bout, providing a positive energy balance post-exercise. This was chosen so that an assessment of: GI (chapter 4A), and basal dose (chapter 5A), on post- prandial glycaemia could be made without being influenced by inadequate carbohydrate intake. This was achieved by providing patients with standardised meals. The combined macronutrient content for all meals collectively was: carbohydrate = ~77%, fat = ~12%, and protein = ~11%. Carbohydrate intake and macronutrient content aimed to match current

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recommendations for exercising type 1 diabetes patients (Riddell and Perkins 2006, Perry and Gallen 2009). The glycaemic index (GI) was determined for all meals.

2.2.5.1 Glycaemic index testing

The GI of all test meals were calculated using the methods described by Wolever and Jenkins et al (1986) (refer to Calculation of blood and interstitial glucose area under the curve; see 2.6). Testing was conducted using non-diabetic controls, following the procedures outlined by Brouns et al (2005). In a randomised and counterbalanced fashion, either a test food or a standard was administered on each separate occasion, so that the test food and the standard were repeated three times by each participant. The standard comprised of a ~10% glucose solution dissolved in still water (75g Dextrose, 750ml water). The standard and test meal were both adjusted relative to body mass (1.0 g.carbohydrate.kg-1BM). A baseline blood sample (1 ml venous blood) was taken, with further periodic sampling at 15 minute intervals up to 135 minutes. All blood samples were analysed for blood glucose using a Biosen (EKF Diagnostic GmbH, Germany; see 2.2.8.1). Following the baseline blood sample, participants consumed either the test food or standard within a 5 minute period.

The area under the glycaemic-response curve (see 2.6) for each food was expressed as a percentage of the mean response to the standard food for each participant, and then averaged to obtain the GI value for the food. If an individual’s value was > 2 standard deviations from the mean, it was considered an outlier. If individuals demonstrated an unrepresentative response to a test food, their results were cross-checked with their response to the standard. If their response to the standard was normal, the test meal was repeated. If a participant’s response to the standard was idiosyncratic, their data were removed from analysis. A GI value was obtained and classified as either low (<55), moderate (56-75), or high (>76) (Kirpitch and Maryniuk 2011). A summary of the composition of each standardised, experimental meal is provided in table 2.2.

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2.2.5.2 Pre-laboratory standardised meals (Chapter 4 and Chapter 5)

In studies 2 and 3 patients received two standardised meals that were consumed on the day of the trial, and before arrival. The composition of the meals was based on the habitual dietary patterns of type 1 diabetes patients (assessed from weighed food diaries from chapter 3 and an online questionnaire). Both meals were tested for palatability. Participants were required to replicate eating times (breakfast ~08:00, lunch ~13:00).

2.2.5.3 Pre-trial meal 1: MEAL 1

The first meal was a cereal-based breakfast meal (frosted flakes, semi-skimmed milk, and peaches) equating to 1.3 g.carbohydrate.kg-1 BM (Table 2.2). Fibre content was negligible across studies.

2.2.5.4 Pre-trial meal 2: MEAL 2

The second meal was a pasta-based lunch (pasta, tomato-based sauce, cheddar cheese, olive oil) equating to 1.3 g.carbohydrate.kg-1 BM (Table 2.2). Fibre content was negligible across studies.

2.2.5.5 Laboratory test meals

Meals consumed in the laboratory were designed to cover the estimated energy cost of the exercise bout. Patients drank water ad libitum.

2.2.5.6 Pre-exercise meal: MEAL 3

The pre-exercise meal was consistent across all three studies. The pre-exercise meal was cereal-based (frosted flakes, semi-skimmed milk, and peaches) equating to 1.0 g.carbohydrate.kg-1BM (Table 2.2). Fibre content was negligible across studies.

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The post-exercise meal for chapter 3 was a pasta-based lunch (pasta, tomato-based sauce, cheddar cheese, olive oil) equating to 1.0 g.carbohydrate.kg-1 BM (Table 2.2). Fibre content was negligible across studies.

2.2.5.8 Post-exercise meals (Chapter 4): MEAL 5 and 6

Each meal was designed to be isoenergetic and was matched for macronutrient content, equating to 1.0 g.carbohydrate.kg-1 BM, but differing in GI (low versus high).

The low GI meal consisted of basmati rice, tomato-based sauce, turkey breast and a isomaltulose orange flavoured drink [10% solution] (Table 2.2). Fibre content was negligible across studies. Food provided 29.8% of carbohydrates, and the drink 70.2%.

The high GI meal (jasmine rice, tomato-based sauce, turkey breast; maltodextrin orange flavoured drink [10% solution]) (Table 2.2). Fibre content was negligible across studies. Food provided 29.8% of carbohydrates, and the drink 70.2%.

2.2.5.8 Post-exercise meal (Chapter 5): MEAL 7

The low GI post-exercise meal from chapter 5 was adopted in this study. The meal (basmati rice, tomato-based sauce, turkey breast; isomaltulose orange flavoured drink [10% solution]) (Table 2.2). Fibre content was negligible across studies. Food provided 29.8% of carbohydrates, and the drink 70.2%.

2.2.5.9 Bedtime snack (Chapter 4): MEAL 8 and 9

Each snack was designed to be isoenergetic and was matched for macronutrient content, equating to 0.4 g.carbohydrate.kg-1 BM as per current recommendations for patients exercising in the evening (Hernandez et al. 2000). However, each meal differed in GI (low versus high).

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The low GI snack (burgen sliced bread [soya and linseed]; isomaltulose orange flavoured drink [10% solution]) (Table 2.2). Fibre content was negligible across studies. Food provided 47.3% of carbohydrates, and the drink 32.9%.

The high GI snack (white sliced bread; maltodextrin orange flavoured drink [10% solution]) was calculated to have a GI of 86. (Table 2.2). Fibre content was negligible across studies. Food provided 47.3% of carbohydrates, and the drink 52.7%.

2.2.5.10 Bedtime snacks (Chapter 5): MEAL10

The bedtime snack in chapter 5 was adopted from the low GI snack in chapter 4 (burgen sliced bread [soya and linseed]; isomaltulose orange flavoured drink [10% solution]) (Table 2.2). Fibre content was negligible across studies. Food provided 47.3% of carbohydrates, and the drink 52.7%.

2.2.5.11 Subsequent morning meal: MEAL 11

The subsequent morning breakfast meal for chapter 5 was a cereal-based meal (frosted flakes, semi-skimmed milk, and peaches) equating to 1.0 g.carbohydrate.kg-1 (Table 2.2). Fibre content was negligible across studies.

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