Physical Activity and Total Daily Energy Expenditure in Older US Adults: Constrained versus Additive Models

Area of Science:

• Gerontology
• Nutritional Science
• Exercise Physiology

Background:

• Understanding the relationship between physical activity (PA) and total energy expenditure (TEE) is crucial for managing energy balance and body weight.
• The influence of energy balance status on the PA-TEE association in older adults remains incompletely understood.

Purpose of the Study:

• To investigate the shape of the relationship between physical activity (PA) and total energy expenditure (TEE) in older adults.
• To explore how energy balance status (negative, stable, or positive) modifies the association between PA and TEE.

Main Methods:

• A cross-sectional study involving 584 older adults (aged 50-74 years).
• Total energy expenditure (TEE) was measured using doubly labeled water, and physical activity (PA) was assessed with accelerometers.
• Nonlinear methods (restricted cubic splines) and percent weight change over 6 months were used to analyze the PA-TEE relationship and energy balance status.

Main Results:

• Total energy expenditure (TEE) generally increased with higher levels of physical activity (PA).
• The association between PA and TEE was approximately linear (P < 0.0001), with no significant curvature (P = 0.920).
• In negative energy balance, TEE remained relatively flat across different PA levels, unlike in stable or positive energy balance where TEE increased with PA.

Conclusions:

• Energy balance status significantly modulates the relationship between physical activity (PA) and total energy expenditure (TEE).
• Physical activity may be effective for weight gain prevention by increasing TEE, particularly in positive energy balance.
• The impact of PA on TEE during weight loss (negative energy balance) may be limited, suggesting a constrained model.