Exercise protects and treats fatty liver with Dr John Thyfault
Jan 8, 2023
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Dr John Thyfault, Professor at the University of Kansas Medical Center, discusses the relationship between exercise, fatty liver, and insulin resistance. He explains how exercise can prevent and treat fatty liver even independently of body weight. The podcast also touches on topics such as liver metabolism during exercise, converting carbohydrates into fats in the liver, the effects of high fitness on fatty liver, and the interconnectedness of organs in the body.
Exercise prevents and treats fatty liver by increasing glucose consumption in muscles, stimulating glucose production in the liver.
The liver plays a vital role in exercise metabolism, maintaining euglycemia and replenishing glycogen levels through fat oxidation.
Estrogen and sex-specific factors influence liver metabolism, highlighting the importance of considering these factors in understanding liver health and the effects of exercise.
Deep dives
Exercise prevents and treats fatty liver and improves liver function
Exercise has been shown to be effective in both preventing and treating fatty liver and improving liver function. When caloric intake exceeds caloric expenditure, it can lead to elevated glucose and fat levels in the blood, causing dysfunction in the liver and resulting in fatty liver. Exercise plays a crucial role in preventing and treating fatty liver by increasing glucose consumption in muscles, which in turn stimulates the liver to produce glucose. Exercise also promotes fat oxidation in the liver, providing energy for gluconeogenesis. The systemic metabolic adaptations and intrinsic changes within the liver itself induced by exercise contribute to the improvement of liver health.
The importance of the liver in exercise metabolism
The liver is a vital organ during exercise metabolism as it maintains euglycemia by producing glucose to meet the energy demands of the body. As exercise increases glucose consumption in muscles, the liver responds quickly by releasing glucose into the bloodstream. Gluconeogenesis, the process of producing glucose in the liver, relies on fatty acid oxidation for energy. Exercise enhances fat oxidation and increases TCA cycle flux in the liver, allowing it to replenish glycogen levels and regulate glucose production. Additionally, the liver plays a role in lipid metabolism, as it synthesizes cholesterol and triglycerides. Maintaining a healthy liver is crucial for overall metabolic health.
The role of estrogen and sex differences in liver metabolism
Estrogen plays a significant role in liver metabolism, as loss of estrogen signaling, such as in post-menopausal women, increases the risk of fatty liver and other metabolic disorders. Female rodents and women with normal ovarian function have been shown to have higher functioning mitochondria in the liver and are protected against fatty liver. Exercise has been found to improve mitochondrial function and insulin sensitivity in the liver, particularly in males. However, with the loss of estrogen signaling, such protective effects diminish. The differences in liver metabolism between sexes highlight the importance of considering sex-specific factors in understanding liver health and the effects of exercise.
Effect of Exercise on Fatty Liver
Exercise plays a crucial role in reducing fatty liver by promoting the oxidation of fat and reducing hepatic fat metabolism. It has been observed that both aerobic exercise and resistance training are effective in lowering liver fat. Even light intensity physical activity is associated with lower liver fat. Higher aerobic capacity is linked to a decreased risk of fatty liver, independent of obesity status. Studies on high and low capacity running rats have shown that high aerobic capacity protects against fatty liver, highlighting the role of exercise in liver health.
Impact of Early Life Stress on Exercise and Obesity
Early life stress has been found to increase the risk of obesity and metabolic dysfunction in animals. However, exercise has been shown to negate the effects of early life stress, resulting in lower obesity rates and improved metabolic health. Studies on animals subjected to early life stress and provided with exercise show that exercise counteracts the detrimental effects of stress on obesity and pain sensitivity. This suggests that exercise during early life may have long-lasting positive effects on metabolic health and stress resilience.
Dr Glenn McConell chats with Professor John Thyfault from the University of Kansas Medical Center. We discuss how when one takes in more calories than they expend, this results in elevated fat and glucose in the blood which disrupts liver metabolism. This can result in fatty liver and insulin resistance. Exercise can prevent and treat fatty liver even independently of body weight. There are important sex differences too. We also touch on ketones, carbohydrates, insulin and the liver.
0:00. Introduction and how got into exercise/liver research
6:48. Liver metabolism during exercise
8:17. Liver and insulin resistance
10:55. Why get fatty liver?
13:28. Liver very adaptable to diet and exercise
15:52. Converting carbohydrates into fats/lipids in the liver
17:03. Why some overweight get fatty liver and others not
18:23. How exercise prevents/treats fatty liver
21:26. Liver tries to compensate for fatty liver but eventually overwhelmed
22:50. Excess calories vs exercise
Difference is turnover rate.
24:50. Liver as an energy converter
27:10. Liver uses fat for energy for new glucose production
28:15. What find of exercise to lower liver fat?
30:32. High fitness is protective of fatty liver
34:20. The body is very integrated across organs.
35:56. Energy balance and the liver
38:05. Can you outrun a bad diet?
40:40. Our dog makes an appearance!
40:46. How does the liver know we are exercising?
42:12. How does exercise make the liver more insulin sensitive?
42:44. Inactivity and the liver
44:11. Genetics/epigenetics
48:50. Sex differences and fatty liver
51:35. Translation of rodent studies to humans
54:09. Ketones, carbohydrates, insulin and the liver
58:10. Weight loss from calorie restriction vs exercise
59:09. Bile acid recycling and exercise capacity
1:02:04. Early life stress and obesity/running amount
1:04:10. Studies that worked out better than expected
1:07:26. Take home messages.
1:09:02. 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.