Intense Exercise May Sabotage Weight Loss Efforts

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Summary: Intense exercise can reduce subsequent physical activity and body temperature, potentially leading to weight gain. The research, conducted on mice, suggests this effect is due to disruptions in the circadian rhythm of the stress hormone corticosterone.

The study indicates that high-intensity exercise decreases overall activity and heat production despite no changes in food intake. These findings emphasize the need to consider the broader impacts of exercise on weight loss strategies.

Key Facts:

  1. Intense exercise reduces subsequent physical activity and body temperature in mice.
  2. The stress hormone corticosterone’s circadian rhythm disruption is linked to this effect.
  3. Despite no change in food intake, reduced activity post-exercise can lead to weight gain.

Source: University of Tsukuba

Exercise is often recommended as an effective strategy for weight loss. However, a recent animal study at University of Tsukuba revealed that intense exercise sessions can decrease subsequent physical activity levels and body temperature, ultimately contributing to weight gain.

This observation may be linked to disruptions in the circadian rhythm of the stress hormone corticosterone and may disturb the synchronous effects of physical activity and body temperature.

Exercise provides numerous health benefits, but its effects on weight loss are sometimes less than expected. This phenomenon may be secondary to reduced physical activity following exercise, but the mechanism is not yet fully understood.

This shows a woman in workout clothing and a scale.
In the high-intensity exercise group, both physical activity and core body temperature after exercise significantly decreased, despite the absence of changes in food intake, leading to body weight gain. Credit: Neuroscience News

The stress hormone corticosterone follows a circadian rhythm, being low at bedtime and at its peak upon waking, and it regulates physical and mental activity levels. Therefore, researchers hypothesized that even a single session of high-intensity exercise can disrupt this rhythm, leading to decreased physical activity and heat production and diminishing the weight loss effect.

To test this hypothesis, mice were divided into three groups as follows: high-intensity exercise, moderate-intensity exercise, and rest. The physical activity and core body temperature, which serve as an index of heat production before and after exercise, of the mice were monitored.

The study is published in Medicine & Science in Sports & Exercise.

In the high-intensity exercise group, both physical activity and core body temperature after exercise significantly decreased, despite the absence of changes in food intake, leading to body weight gain.

Furthermore, the researchers observed the disruption in the synchrony between physical activity and body temperature. Together, they confirmed a positive correlation that relatively low blood corticosterone levels during wake times were associated with less physical activity.

The findings indicate that a single session of high-intensity exercise can disrupt the circadian rhythm of corticosterone, leading to reduced physical activity and body temperature and body weight gain.

This study highlights the importance of considering not only the calories burned during exercise but also the subsequent activity levels and circadian rhythm when designing exercise regimens for effective weight loss.

About this exercise and weight loss research news

Author: Daisuke Funabashi
Source: University of Tsukuba
Contact: Daisuke Funabashi – University of Tsukuba
Image: The image is credited to Neuroscience News

Original Research: Closed access.
“Acute Vigorous Exercise Decreases Subsequent Non-Exercise Physical Activity and Body Temperature Linked to Weight Gain” by Daisuke Funabashi et al. Medicine & Science in Sports & Exercise


Abstract

Acute Vigorous Exercise Decreases Subsequent Non-Exercise Physical Activity and Body Temperature Linked to Weight Gain

Purpose 

Exercise benefits the body and mind, but its weight loss effect is less than generally expected. Although this phenomenon is likely due to an exercise intensity-dependent decrease in non-exercise physical activity (NEPA), resulting in a decrease in non-exercise activity thermogenesis, the underlying mechanisms and effects of exercise intensity remain unknown. Here we show that acute vigorous exercise decreases subsequent NEPA and body temperature (BT) in association with body weight gain.

Methods 

Adult male C57BL/6 J mice were categorized into three groups: sedentary, moderate exercise, and vigorous exercise, with exercise groups undergoing a 30 min treadmill session. Using an intraperitoneally implanted activity monitor, NEPA and BT were monitored for two days before and three days after exercise. The daily synchrony between NEPA and BT was evaluated using a cross-correlation function. Plasma corticosterone was also detected 6 and 24 h after exercise.

Results 

Notably, Only the vigorous exercise group exhibited a decline in both NEPA and BT, resulting in body weight gain the following day, despite no observed changes in food intake. Furthermore, vigorous exercise induces a distinct delay in the daily dynamics of NEPA compared to BT. A positive correlation was observed between plasma corticosterone levels and changes in NEPA levels before and after exercise across all exercise groups.

Conclusions 

Our findings provide evidence for vigorous exercise-specific reduction in subsequent NEPA, BT, and their synchrony linked to weight gain, likely due to the disturbed circadian rhythm of corticosterone. This is an initial investigation redefining the significance of exercise intensity in beneficial effects beyond the energy expenditure of the exercise itself.

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