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Does prolonged exercise alter diet-induced thermogenesis?
M Ohnaka1, M Iwamoto, S Sakamoto
1Department of Nutrition, School of Medicine, Faculty of Integrated Arts, University of Tokushima, Japan. ohnaka@nutr.med.tokushima-u.ac.jp
Annals of Nutrition & Metabolism
|January 23, 1999
Summary
Exercise impacts diet-induced thermogenesis (DIT) by altering insulin secretion and autonomic nervous system balance. While DIT itself didn't change, these underlying physiological shifts suggest complex interactions affecting energy metabolism.
Area of Science:
- Metabolism and Endocrinology
- Exercise Physiology
Background:
- Diet-induced thermogenesis (DIT) is primarily an insulin-mediated process linked to nutrient synthesis.
- Exercise is known to influence metabolic responses, but its specific effect on DIT requires further clarification.
Purpose of the Study:
- To investigate the impact of prior exercise on diet-induced thermogenesis (DIT) at rest.
- To elucidate the mechanisms behind exercise-induced alterations in DIT, focusing on insulin sensitivity, substrate oxidation, and autonomic nervous system activity.
Main Methods:
- Six healthy men underwent two experimental conditions: an 8-hour rest period after 1 hour of cycling exercise, and an 8-hour rest period without prior exercise.
- Diet-induced thermogenesis was assessed after a standardized meal was administered at 12:30h on both experimental days.
- Heart rate variability was analyzed to assess autonomic nervous system tone (sympathetic and parasympathetic) during the recovery period.
Main Results:
- No significant difference in DIT was observed between the exercise and non-exercise conditions.
- Exercise led to increased insulin sensitivity and free fatty acid oxidation, potentially enhancing glucose-to-glycogen conversion.
- Post-meal insulin secretion (insulin/glucose ratio) was significantly reduced after exercise (p < 0.05).
- Heart rate variability indicated increased sympathetic and decreased parasympathetic tone during the post-exercise recovery period (p < 0.05).
Conclusions:
- Prior exercise does not significantly alter direct diet-induced thermogenesis in healthy men.
- Exercise influences underlying metabolic factors, including insulin sensitivity, substrate oxidation, and autonomic balance, which may counteract each other regarding DIT.
- The complex interplay of these factors suggests that changes in DIT are multifactorial and depend on the balance between opposing physiological responses.