Ch21 The Role of Physical Activity in Weight Loss and Weight Loss Maintenance

1. Ch21 The Role of Physical Activity in Weight Loss and Weight Loss Maintenance Rosae Calvo 11/01/13

2. Outline • Introduction • Relationship between physical activity and weight changes • Measurement of physical activity • Methods and theories to initiate and maintain physical activity among overweight/obese • Diversity issues in physical activity and weight loss • Recommendations • Activity

3. Introduction • Weight management efforts in overweight/obese usually require calorie restriction in addition to physical activity • Best predictor of sustained weight loss • Prevents loss of lean body mass and helps to maintain energy balance

4. Relationship between physical activity & weight changes • Energy balance – involves complex physical and behavioral mechanisms INTAKE EXPENDITURE Weight Maintenance Calories Eaten EXPENDITURE INTAKE Calories Burned EXPENDITURE INTAKE Weight Gain Weight Loss

5. Relationship between physical activity & weight changes Energy intake 152 kcal 95 kcal 125 kcal • Affected by biological, psychological, social, and developmental processes

6. Relationship between physical activity & weight changes Energy expenditure = Basal metabolism + TEF + PA • Basal Metabolism – energy required to sustain life at rest • Breathing, blood circulation, thermoregulation • 60-75% total daily energy expenditure in sedentary adults • 1 kcal/kg weight/hour • Calculate BEE for a 150lb and 400lb person • Thermic effect of food • Digestion, absorption, nutrient storage • 10% total daily energy expenditure

7. Relationship between physical activity & weight changes Table 21-1 Kcal expended per hour across activities for a 90 kg (198 lb) person Energy Expenditure • Activity thermogenesis – skeletal muscle activity • Voluntary and involuntary movements • Exercise-related activity and non-exercise activity • 15-50% of total daily energy expenditure • Factors: occupation, leisure time PA, households tasks, self-care activities

8. Difference between Physical Activity and exercise • Physical activity: any movement that results in skeletal muscle contraction and increases in energy expenditure • Non-exercise activity thermogenesis (NEAT): occupational tasks, standing, walking, talking, tapping, playing an instrument, shopping, etc. • Exercise: planned, structured, and repetitive bodily movement with primary goal of improving/maintaining physical fitness

9. Difference between Physical Activity and exercise NEAT vs. Exercise • Data suggests NEAT contributes more to increased energy expenditure compared to structured exercise; consider a lifestyle approach rather than structured exercise • One study showed NEAT is just as effective as exercise in improving blood lipid levels and blood pressure • Weight-loss option for overweight/obese: Diet + NEAT

10. Effect of physical activity on weight • Prevention of weight gain • Average weight gain: 1-2 lb/year • Prevented by expending ~100kcal through physical activity per day or by reducing intake by ~100 kcal/day • 15-30 min. of daily moderate-intensity activity may prevent weight gain • 1-1.5 miles of walking • 2000-3000 steps/day • Varies by the individual; genetic factors may increase amount of work needed

11. Effect of physical activity on weight • Initial weight loss for sedentary individuals • Scientific evidence suggests greater weight loss is achieved through dieting or dieting + PA • For sedentary/unfit individual, it is more feasible to tip the energy balance equation by reducing calorie intake

12. Effect of physical activity on weight • Weight loss maintenance • Important for preventing weight regain, loss of lean muscle mass, and for improving health • National Weight Control Registry (NWCR): Duration and intensity levels associated with weight loss maintenance • Success linked with reducedcalories and reports of >1 hr of moderate-intensity activity daily • Decreases in activity associated with weight regain

13. Effect of physical activity on weight • Resistance training – e.g. weightlifting • Theory: Increase in fat-free mass results in weight loss by increasing RMR • Reality: Preserves lean muscle mass in dieters but does not maintain or increase RMR • Benefits • Increase strength increases likelihood of sustained exercise  increase energy expenditure • Maintains bone density

14. Measurement of physical activity • Criterion methods – gold standard; expensive, inaccessible; rarely used in clinical settings • Doubly-labeled water – measures total energy expenditure or metabolic rate; • Indirect calorimetry – determines energy expenditure by measuring volume of expired air from lungs and analyzing oxygen-carbon dioxide content

15. Measurement of physical activity • Objective methods • Pedometers – motion sensory that measures steps taken while walking/running • Accelerometers – motion sensory that provides an estimate of overall physical activity; sensitive to all body movement • Heart rate monitors

16. Measurement of physical activity • Subjective/Self-report methods – inexpensive, frequently used in epidemiological and intervention studies • Diaries • Interviews • Questionnaires

17. theories to initiate and maintain physical activity among overweight/obese • Transtheoretical Model (TTM): individuals progress in a non-linear fashion through 5 stages when changing any health-related behavior

18. theories to initiate and maintain physical activity among overweight/obese • Social cognitive theory: incorporates general strategies for progressing through stages of change; based on psychosocial, environmental, and behavioral factors • Increase confidence in ability to initiate and maintain physical activity • SMART goals • Focus on progress and reinforcement of successes • Techniques: modeling, self-regulation strategies, develop social support Specific, Measurable, Attainable, Relevant, Timely

19. theories to initiate and maintain physical activity among overweight/obese • Health Belief Model – individuals will engage in physical activity if they perceive their sedentary lifestyle to be a health threat and if they believe that activity will be helpful in reducing that threat

20. theories to initiate and maintain physical activity among overweight/obese • Theory of Planned Action – health behaviors are not only a function of health beliefs, but are also associated with other factors, such as attitude toward a health behavior, perception of social norms, self-efficacy, and locus of control

21. theories to initiate and maintain physical activity among overweight/obese • Active Living Every Day (ALED) – promotes adoption and maintenance of physical activity among adults • Principles: • Physical activity need not be strenuous or time-consuming to benefit health. • People are more likely to become and stay physically active when taught appropriate lifestyle skills

22. Diversity issues in physical activity and weight loss: Underserved populations • Increased risk of obesity in racial/ethnic minority groups (African Americans, Hispanics) • Less likely to participate in weight loss interventions, have weight loss success, be physically active • More likely to consume a poorer diet • Healthy People 2010 goal: Eliminate health disparities across gender, race/ethnicity, and geographic location • Majority of studies based on the predominantly White population

23. Summary • Weight gain prevention and weight loss maintenance involves increasing physical activity through increases in NEAT or structured exercise • Need to shift from a “one-size-fits-all” approach to an individualized approach • The amount of physical activity needed to achieve health benefits is less than the amount needed to achieve weight loss

24. Recommendations • For optimal health benefits: 30 min/day moderate intensity, 5 days per week • Bouts of at least 10 min. • Resistance exercise twice a week • For weight maintenance: 30-60 min/day • For weight loss maintenance: 60-90 min/day • For children: 1 hr/day of moderate to vigorous activity • Resource: www.health.gov/paguidelines

25. Questions?

26. Activity: Based on the following motivational quotes, what do you think are some of the biggest misconceptions about physical activity and weight loss?

27. Thank you!