Continuous Glucose Monitors in Ultramarathon with Amy-Lee Bowler, PhD (c) | KoopCast Episode #190
Episode overview:
Amy-Lee Bowler is a PhD candidate at the University of Bond in AUstralia. Her research seeks to understand the current practice pathways and subsequent dietary management used by sports dietitians when assessing and managing energy availability in athletes.
Episode highlights:
(25:45) Personalization of blood glucose: new study on standard glucose levels in athletes, “metabolic flexibility”, lipid oxidation, tighter glucose control in endurance athletes, intensity, duration, diet, and training level all change blood glucose
(35:41) CGMs for identifying acute low energy availability: subjective assessments might be more valuable, examples
(55:30) CGMs are not tools for athletes: it is difficult for athletes to determine anything useful from the data, examples, currently CGMs must be used with practitioners
Our conversation:
(0:00) Introduction: setup for applications and considerations of continuous glucose monitors (CGMs) in sport, history of CGMs, future applications
(2:06) Setup: dissecting popular training tools, CGMs are conspicuous, public curiosity
(3:42) Amy-Lee’s background: assessing low energy availability in athletes, investigating sport-specific CGMs, exponential public interest, examples
(6:33) Practitioner-focused research: perspective as a sports dietician, working with swimmers and skateboarders, practicality and accessibility of Amy’s paper
(8:56) History of CGMs: clinical tools entering the sports space, use in diabetic populations, a user-friendly alternative to other invasive methods of measuring glucose, details of clinical use
(13:18) Bringing CGMs into sport: the elusive goal of optimizing fueling patterns, sports biosensors versus diabetic GCMs, commercial options
(16:59) Glucose cascade overview: carbohydrates become blood sugar, prompting the pancreas to create insulin, insulin aids cellular blood sugar uptake, sugars are used for energy or stored, blood sugar subsequently falls
(18:14) How CGMs work: measuring interstitial fluid, estimation of blood glucose via the glucose-oxidase reaction, 10 minute time lag between blood glucose and measurement
(19:48) Value proposition of CGMs: use as a fuel gauge, lack of evidence to support this claim, mixed findings from case studies, CGMs may or may not be useful, powerful marketing
(24:27) Complications of glucose monitoring: blood glucose response to carb intake, personalization and significance of CGM data, vehicle fuel gauge analogy
(25:45) Personalization of blood glucose: new study on standard glucose levels in athletes, “metabolic flexibility”, lipid oxidation, tighter glucose control in endurance athletes, intensity, duration, diet, and training level all change blood glucose
(28:34) Blood glucose in males versus females: females have lower blood glucose levels, intensity example, recap of complications to blood glucose monitoring
(30:02) Caveats: “metabolic flexibility” as a poorly defined term, reducing something as complex as fueling to a single number is problematic, HRV example
(31:55) CGMs for low-carb states: potential applications for low-carb interventions, lack of supporting research, first validate the basics
(34:43) Caveats for low-carb interventions: the acute adaptation is well demonstrated, the cost is unknown, practical challenges, master the training basics
(35:41) CGMs for identifying acute low energy availability: subjective assessments might be more valuable, examples
(38:48) Challenges with measuring RED-S: identifying low energy availability takes time, episode 121 with Ida Heikura, issues with measuring dietary intake and training load, DEXA scans, bone density and menstrual cycle dysfunction, blood testing
(41:51) CGMs for avoiding RED-S: sports dieticians typically use inaccurate tools for measuring low energy availability, two papers suggesting potential, changes in blood glucose over 5 days, changes in interstitial fluid in starved military personnel
(45:15) Amy-Lee’s study: constraints, potential for measuring energy deficit, complications with exercise, future research
(46:31) Identifying intermittent fasting versus RED-S: lack of research, acute versus chronic energy deficits, adapting to low glucose availability, challenges with measurement
(48:34) CGMs in context: CGMs will always need to be used in conjunction with other tools, applying context to blood glucose data, HRV and heart rate example
(50:17) Fuel gauge proposition: theorizing a perfect scenario, Supersapiens example, integration between dietary intake recording software, blood glucose, and training data
(53:25) Conveying data to athletes: challenges, contextualizing data, examples, the need for practical data analysis
(55:30) CGMs are not tools for athletes: it is difficult for athletes to determine anything useful from the data, examples, currently CGMs must be used with practitioners
(57:43) Koop’s takeaway: machine learning interventions and outcomes on a personal basis over many years, dummy gauges example
(59:39) Building our knowledge on CGMs: more research and practical use is necessary, theoretical use cases often outpace practical knowledge
(1:00:55) Wrap-up: Amy-Lee’s upcoming paper on low energy availability, where to find Amy-Lee’s research
(1:03:37) Outro: giving thanks, check out Amy-Lee’s paper, commitment to no sponsorship and supporting the KoopCast via Training Essentials for Ultrarunning
Additional resources:
The Use of Continuous Glucose Monitors in Sport: Possible Applications and Considerations
Low Energy Availability in female Athletes: from the lab to the field
Sports Dieticians Practices for Assessing and Managing Athletes at Risk for Low Energy Availability
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