Research Question: Does the advice and guidance to consume a long-term low-carbohydrate
breakfast impact blood glucose levels in people with type 2 diabetes?
Objectives
The specific aims are to conduct a RCT to determine if advice and guidance to consume a
low-carbohydrate breakfast, compared to standard guidelines control breakfast, for one
year:
Improves glycemic control assessed by HbA1c (primary outcome) in individuals with type 2
diabetes (T2D); Improves glycemic variability and lowers postprandial hyperglycemia in
individuals with T2D; Reduces body weight and fat mass in individuals with T2D; Reduces
feelings of hunger and consequently lowers daily energy and carbohydrate intake in
individuals with T2D.
Hypothesis:
Advice and guidance to consume a low-carb high-fat breakfast, compared to a standard
control low-fat breakfast over 1 year will reduce HbA1c levels; When compared to a
low-fat breakfast, low-carb high-fat breakfast will improve glucose monitoring metrics.
Compared to a low-fat breakfast, a low-carb high-fat breakfast will lower feelings of
self-reported hunger; A low-carb high-fat breakfast will improve body composition in
individuals with T2D.
Background Information
In the years leading up the pandemic (2016 to 2019), almost 1 in 10 Canadian adults aged
20 to 79 (9%) had diabetes. The prevalence of diabetes ranged from 1% of Canadians aged
20 to 39 to almost one in five seniors aged 60 to 79 (18%) (Statistics Canada). The high
prevalence is associated with a high personal, clinical and economic burden, with
diabetes resulting in approximately 15,700 deaths each year in Canada (Cho et al., 2018).
Clearly, strategies to improve glucose control and reduce the burden of T2D are
attractive from a quality of life and economic standpoint.
Lowering dietary carbohydrate intake has been shown to improve blood glucose control and
is now recognized as an evidence-based nutritional strategy in T2D (Churuangsuk et al.,
2020). However, low-carbohydrate diets are often criticized as being too difficult to
sustain in the long-term. One potential strategy is to limit carbohydrate intake at only
one daily meal. Since the largest hyperglycemic spike usually occurs in the morning after
the first meal, manipulating the carbohydrate content of the breakfast may be a simple
strategy to improve glycemic control in people with T2D.[ Long-term trials specifically
examining low-carbohydrate egg-based breakfasts are lacking. To our knowledge, our last
RCT (Oliveira et al., AJCN 2023) is the most recent and robust evidence examining the
effects of a low-carbohydrate breakfast on glucose control in T2D up to now (described in
detail below). Pedersen et al. (2016) demonstrated in T2D patients that excluding
carbohydrates from the first meal of the day could mitigate the significant glucose spike
typically observed after breakfast. Similarly, Park et al. (2014) found that a
high-protein breakfast reduced postprandial glucose concentrations without exacerbating
the glucose response to subsequent meals, suggesting that incorporating more protein into
breakfast could be a therapeutic approach for T2D management.
Considering our publications demonstrating enhanced glycemic control in T2D patients
following a low-carbohydrate breakfast (Chang et al., 2019 and Oliveira et al., AJCN
2023), alongside existing research indicating the health benefits of "bigger" and
high-protein breakfasts in T2D, there is compelling justification for conducting a
longer-term, well-designed, adequately powered randomized controlled trial (RCT). We
hypothesize that consuming a low-carbohydrate breakfast for 1-year will improve blood
glucose control and be recognized as a scientifically substantiated, evidence-based
nutritional strategy for T2D, with promise for potential incorporation into clinical
practice guidelines.
Research Method
Overview
Two-hundred eighty (N=280) individuals with diagnosed T2D (30-79 years old), will be
recruited from across Canada for a 1-year parallel-group remotely-delivered RCT through
online and newspaper advertising, emails, third-part recruitment agency as well as word
of mouth. Participants will be randomized to consume a low-carbohydrate breakfast (LC,
n=140) or a low-fat "standard care" control breakfast (CTL, n=140) for 12 months,
stratified by age (30-50, 51-79) and biological sex (M/F).
Participants will continue to take any medications as instructed by their physicians
throughout this real-world trial but will be asked to report any changes that occur to
study personnel over the 1-year period.
Experimental conditions
A 1-year parallel-group RCT is proposed. Due to the nature of the dietary intervention
trial, study participants and investigators will not be blinded - however, masking will
be implemented wherever possible (e.g., for data analysis). Eligible participants will be
randomized to either the:
i) Low Carbohydrate Breakfast (LC, n=140) or ii) Low-fat "standard care" Control
Breakfast (CTL, n=140) Both breakfasts will be consumed daily for a period of 1-year.
Breakfast options Similar to our previous trial, each group will be provided with an
initial menu of 12 recipes consisting of ~400-500 kcal from which to choose each morning.
LC breakfasts will contain <10% carbohydrates, 60-75% fat, and 15-30% protein (e.g.,
omelette with cheese) and CTL breakfasts will contain 45-70% carbohydrates, 20-40% fat,
15-25% protein (e.g., oatmeal with berries). Participants will be instructed to have
their first meal of the day (before 12pm) as per recipes and to upload a daily photo of
their breakfast to confirm compliance. As in our previous low-carbohydrate breakfast
study no instructions will be provided for other meals as the goal is to be free-living
with minimal intervention and increased potential for implementation and translation to
real-world life.
Dietary intake assessment Participants will be guided to register three 3-day food
records (2 weekdays and 1 weekend day) at baseline, 3, 6, 9 and 12 months of the trial
through REDCap-UBC links. Macronutrient composition and total caloric intake will be
calculated using ESHA software to determine any group differences across time.
Hunger and Fullness questionnaire Participants will complete a 100 mm Visual Analog
Scales (VAS) to measure self-reported hunger, fullness and desire for sweet and savoury
foods at multiple timepoints across one day at baseline, 3, 6, 9 and 12 months. They will
be advised to fill out the survey after breakfast.
GODIN Leisure-Time Exercise Questionnaire Participants will be asked to report changes to
their physical activity by completing a GODIN questionnaire through a REDCap-UBC link
sent by email at baseline and end of the trial. The Godin Leisure-Time Exercise
Questionnaire allows the assessment of self---reported leisure---time physical activity.
Chronotype survey (exploratory outcome) Chronotype will be determined using the
Morningness-Eveningness questionnaire (MEQ) send through a REDCap-UBC link by email at
baseline.
Blood testing Blood samples will be collected at baseline and after 12 months for HbA1c
and lipids (triglycerides, total, HDL, and LDL cholesterol) at the nearest local
laboratory with lab requisition provided by research team.
Anthropometry Anthropometric measures (height, body weight, and waist circumference) will
be assessed at baseline, 3, 6, 9 and, 12 months during Zoom calls with the dietitian.
Glucose monitoring Participants in both groups will receive a flash glucose monitoring
sensor (FreeStyle Libre 2) at baseline, to record their glucose levels for 14 days before
starting the breakfast recipes. Once intervention has started, they will wear the flash
glucose monitoring sensor for 14 days at 6 and 12 months to capture changes related to
dietary approach. The sensor will be an informative tool for glycemic control in both
groups by measuring daily postprandial hyperglycemia and providing the data necessary to
calculate 24-hour average, post-meal incremental areas under the curve (iAUC), and
glycemic variability.