Mice on a Diet Keep Exercising: A New Twist on Exercise and Energy

A recent study from UC Riverside reveals that calorie restriction does not significantly impact the exercise habits of mice, challenging the common belief that dieting diminishes workout energy.

Published in the journal Physiology & Behavior, the research demonstrates that reducing calories by 20% did not notably affect the amount of distance mice chose to run daily. The study aimed to understand how cutting food intake influences voluntary exercise, with implications for both wild animals experiencing food scarcity and humans on diets.

Obtaining precise data on human exercise can be challenging due to the difficulty of measuring various forms of physical activity. However, tracking lab mice is more straightforward since they typically enjoy running on wheels for extended periods. In this study, mice maintained their running activity regardless of food intake.

The researchers observed that even with a 20% calorie reduction, mice continued to run at similar levels. When calorie intake was cut by 40%, there was only a slight decrease in running distance, particularly among the "high runner" mice, who initially ran three times more than normal mice. Despite the reduction, the high runners still showed high levels of activity.

The study found that running seems to be a self-rewarding behavior, likely due to the release of dopamine and cannabinoids in the brain, which might explain why mice kept running despite reduced food intake. Additionally, body mass did not significantly decrease with a 20% reduction in calories, and only a minor drop was observed with a 40% reduction, similar to weight loss seen in humans on diets.

This research sheds light on why some individuals are motivated to exercise while others are not, and could offer insights into managing physical activity and body weight in various contexts. Future studies are planned to explore how calorie restriction affects voluntary exercise and body mass more deeply.

Understanding these dynamics is crucial for wildlife conservation and for people seeking to improve their health without compromising their physical activity levels. The study indicates that calorie reduction does not necessarily mean reduced exercise, challenging the idea that dieting must lead to decreased physical activity.