Asymmetric weight gain and loss from increasing and decreasing exercise

Area of Science:

• Exercise physiology
• Human metabolism
• Weight management

Background:

• Physical activity levels influence body weight, with increased activity promoting weight loss and decreased activity leading to weight gain.
• The symmetry or asymmetry of weight changes in response to fluctuations in physical activity is not well understood.
• Asymmetric weight changes could explain weight fluctuations in individuals with seasonal or irregular exercise patterns.

Purpose of the Study:

• To investigate whether the magnitude of weight loss from increased physical activity is equal to the magnitude of weight gain from decreased physical activity.
• To determine if weight changes are symmetric across different levels of exercise.
• To identify thresholds for symmetric weight change in response to exercise modifications.

Main Methods:

• A longitudinal study comparing changes in adiposity with running distances in a large cohort of men and women.
• Analysis of exercise changes (increase or decrease in running distance) over a 7.7-year follow-up period.
• Comparison of weight changes associated with varying levels of exercise reduction and increase.

Main Results:

• Decreases in running distance resulted in significantly greater weight gain compared to weight loss from equivalent increases in distance, particularly at lower exercise volumes.
• Weight gain from reduced exercise was more pronounced at lower activity levels (0-8 km/week) than at higher levels (32-48 km/week).
• Statistically significant weight loss was observed only above specific exercise thresholds (16 km/week for women, 32 km/week for men), with weight loss equaling or exceeding weight gain above these points.

Conclusions:

• Weight gained from exercise reductions below 15 kcal/kg/day (women) or 30 kcal/kg/day (men) may be irreversible even with subsequent increases in activity.
• Asymmetric weight changes, where weight gain from inactivity is greater than weight loss from activity, can contribute to overall weight gain in less active individuals.
• Current guidelines for total energy expenditure align with the identified exercise thresholds for symmetric weight change, suggesting a basis for weight management strategies.