NST 10 Why do almost all diets fail? Dynamic nature of energy balance; what works

Flashcards covering key concepts from the lecture on energy balance, diet failure, weight maintenance, fitness vs. fatness, and the role of muscle mass.

Dynamic (Adaptive) Nature of Energy Balance

The body's ability to adjust its energy expenditure in response to changes in energy intake, making it challenging to maintain weight loss.

Fitness vs Fatness Question

A discussion point exploring whether a person can be considered 'fit' despite being 'fat,' and the health implications of this relationship.

Muscle Mass

A new biomarker highlighted in relation to energy balance and overall health.

Energy Imbalance

A state where energy intake (calories consumed) exceeds energy expenditure (calories burned), often cited as a cause of obesity.

Finely Balanced System (Energy)

Describes the body's precise regulation of energy, where annual caloric intake in the millions is typically offset to keep weight stable within a small range.

Adaptive Energy Expenditure (EE)

The physiological adjustment by which the body burns more or fewer calories each day in response to changes in energy intake, as demonstrated in overfeeding and underfeeding studies.

Leibel et al, N Engl J Med, 1995

A seminal study cited for demonstrating the adaptive nature of energy expenditure in response to induced weight gain or loss.

Dynamic Energy Balance Equation

A principle that acknowledges the body's adaptation in energy expenditure to changes in energy intake and body weight, explaining difficulties in long-term weight maintenance.

Body Weight Defense

The inherent physiological mechanisms (e.g., reduced energy expenditure, increased appetite) by which the human body resists changes in its established body weight.

Harsh Masters with a Long Memory

A metaphor used to describe the persistent defense mechanisms of fat stores, implying the body works actively to regain lost weight over an extended period.

Successful Long-Term Weight Loss Maintenance

Characterized by individuals who consistently engage in approximately 3,000 KCal/week of voluntary exercise and adhere to low energy density/low-fat diets.

Voluntary Activity and Weight Loss

Important because it not only directly burns calories but also promotes changes in body composition, such as increased muscle mass, which boosts Resting Energy Expenditure.

Cardiorespiratory Fitness

The body's capacity to perform aerobic work, operationally measured by treadmill exercise capacity, involving efficient oxygen delivery to and consumption by tissues.

Aerobic Work Capacity

The conceptual definition of fitness, representing the body's ability to sustain physical activity that requires oxygen.

Lean Unfit Men vs. Obese Fit Men (Mortality)

Research shows that lean men with low cardiorespiratory fitness have higher all-cause and cardiovascular disease mortality rates compared to obese men who are fit.

Skinny Fat

A colloquial term referring to individuals who appear lean but possess low cardiorespiratory fitness, potentially facing health risks comparable to or even greater than some obese individuals.

Health Benefits of Fitness

Include direct effects like improved mitochondrial function and organ perfusion, and indirect effects such as positive alterations in blood lipids, blood pressure, and insulin sensitivity.

Resting Energy Expenditure (REE)

The amount of energy burned by the body at rest, with its primary determinant being lean body mass, approximately half of which is muscle.

Muscle's Role in Energy Burning

As a significant component of lean body mass, muscle tissue substantially contributes to Resting Energy Expenditure, meaning a higher muscle mass leads to more calories burned even during inactivity.