How does exercise affect metabolism after eating with Dr Javier Gonzalez
Jan 1, 2023
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Dr Javier Gonzalez, Professor from the University of Bath, discusses carbohydrate metabolism at rest and during exercise, the effects of exercise on metabolism after a meal, and glycogen resynthesis. They touch on the use of tracers to determine glucose turnover and the impact of different types and amounts of carbohydrates. They also explore the importance of not immediately replenishing carbohydrates after exercise and the effects of carbohydrate ingestion on exercise performance.
Different types of carbohydrates have varying effects on glucose levels, muscle glycogen synthesis, and liver glycogen levels during exercise.
To maximize glycogen resynthesis after exercise, it is recommended to consume around 1 gram per kilogram of body weight per hour of carbohydrates within the first four hours post-exercise.
Further research is needed to explore the relationship between glycogen and insulin sensitivity, as well as the influence of carbohydrate availability on energy balance behaviors and metabolic health.
Deep dives
Effect of Different Types of Carbohydrates on Glucose and Glycogen Metabolism
The podcast episode explores the effect of different types of carbohydrates on glucose and glycogen metabolism. The research focuses on comparing and contrasting glucose and glycogen metabolism at rest and during exercise. It discusses the impact of different types of carbohydrates on glucose levels, muscle glycogen synthesis, and liver glycogen levels. The episode also delves into the effects of exercise on glycogen synthesis in the liver and muscle, specifically looking at the difference in carbohydrate ingestion, such as glucose, fructose, and glucose-fructose mixtures. It highlights the importance of carbohydrate availability before, during, and after exercise and its impact on glycogen stores.
The Role of Carbohydrate Intake in Exercise Performance and Glycogen Resynthesis
The podcast episode addresses the role of carbohydrate intake in exercise performance and glycogen resynthesis. It explains that for maximizing glycogen resynthesis after exercise, ingestion of around 1 gram per kilogram of body weight per hour of carbohydrate is recommended. This should be done within the first four hours post-exercise. The discussion touches upon the influence of dietary carbohydrates on muscle glycogen and liver glycogen. The episode reveals that a combination of glucose and fructose-containing carbohydrates enhances liver glycogen storage. It also suggests that for athletes and those needing multiple daily performances, optimizing glycogen stores through carbohydrate intake is crucial. However, for the average person and non-elite athletes, a normal mixed diet without excessive carbohydrate intake would suffice.
Exploring the Relationship between Glycogen and Insulin Sensitivity
The podcast episode mentions the need to investigate the relationship between glycogen and insulin sensitivity further. The discussion emphasizes understanding the potential involvement of liver glycogen in exercise-induced improvements in insulin sensitivity. This area of research investigates the role of glucose effectiveness and its impact on metabolic health. The episode also mentions studies on manipulating sugar content and total carbohydrate intake to explore their effects on energy balance behaviors, physical activity levels, and overall metabolic health. The goal is to delve into the influence of carbohydrate availability on propensity for physical activity, energy intake, and metabolic markers.
Effect of Food Matrix on Carbohydrate Digestion
The food matrix, such as intact cells or multi-stage processing, can influence the digestion of carbohydrates. Whole foods with intact cells are digested more slowly, while processed foods are digested more rapidly. The rate of glucose or fructose appearance in the circulation is affected by the food matrix.
Carbohydrate Loading and Performance
For most healthy individuals with a normal carbohydrate intake, glycogen stores are sufficient to sustain about 90 minutes of intense exercise before becoming significantly depleted. While small amounts of carbohydrate intake during exercise may not spare glycogen, it can still improve performance, possibly due to sensory cues. However, ingesting carbohydrates during prolonged exercise can significantly enhance performance by providing metabolic fuel.
Dr Glenn McConell chats with Professor Javier Gonzalez from the University of Bath. We discuss carbohydrate (CHO) metabolism at rest when fasted vs fed, during exercise when fasted vs fed and the effects of exercise on metabolism after a meal. We also discuss muscle and liver glycogen resynthesis and the effects of different types and amounts of carbohydrate. Finally, we touch on Javier’s study with ketone supplementation and EPO.
0:00. Introduction
2:23. How got into exercise research
4:43. Metabolism at rest when fasted and in response to a meal
7:30. Effect of exercise on metabolism after a meal
9:15. Transient hypoglycemia during exercise after a meal (in some)
10:04. Effect of increasing amounts of glucose on blood glucose levels
12:21. Tracer studies to determine glucose turnover/flux
The glucose concentration does not tell us the rate of glucose appearance and disappearance. Need tracer methodologies to determine this.
18:06. Maximum rate of CHO can ingest during exercise
Glucose vs fructose etc.
20:55. Glycogen resynthesis after exercise
23:00. Indirect pathway of glucose metabolism in the liver
24:49. If exercising once per day generally don’t need to maximize glycogen levels
29:23. Glucose, fructose vs normal food/meals
31:17. Generally don’t need CHO loading or CHO ingestion if exercise is ~1hr
33:24. CHO backloading
35:52. Glucose spikes after eating are generally normal physiology
After a meal it is normal to have a “spike” (excursion) in glucose concentrations.
38:45. Research studies using fasted vs fed individuals
40:38. Time to exhaustion vs time trials
43:34. CHO ingestion reduces liver glycogen use
Is there a sensor from the liver to the brain that effects exercise performance?
46:28. Fasting, exercise intensity and CHO needs
49:03. Ingesting CHO and lactate measurements
50:50. Continuous glucose monitors
53:40. Often doesn’t find what he expected to in research
55:08. What’s he excited about right now?
58:35. Liver glycogenolysis vs gluconeogenesis during exercise
59:59. High exercise intensity and CHO metabolism
1:01:47. Different ways of measuring insulin sensitivity
The so-called gold standard to determine insulin sensitivity is the euglycemic hyperinsulinemic clamp but it’s so different to eating meals.
1:04:58. Ketones, exercise and EPO
1:07:32. Endurance athletes generally benefit from high CHO diets
1:09:04. Take home messages
1:12:08. Outro (9 seconds)
Inside Exercise brings to you the who's who of exercise metabolism, exercise physiology and exercise’s effects on health. With scientific rigor, these researchers discuss popular exercise topics while providing practical strategies for all.
The interviewer, Emeritus Professor Glenn McConell, has an international research profile following 30 years of Exercise Metabolism research experience while at The University of Melbourne, Ball State University, Monash University, the University of Copenhagen and Victoria University.
He has published over 120 peer reviewed journal articles and recently edited an Exercise Metabolism eBook written by world experts on 17 different topics (https://link.springer.com/book/10.1007/978-3-030-94305-9).
Connect with Inside Exercise and Glenn McConell at: