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

Rosae Calvo11/01/13

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

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

Relationship between physical activity & weight changes

• Energy balance – involves complex physical and behavioral mechanisms

Weight MaintenanceCaloriesBurned

Weight Gain

CaloriesEaten

Weight Loss

INTAKE EXPENDITURE

INTAKE

EXPENDITURE INTAKE

EXPENDITURE

Relationship between physical activity & weight changes

Energy intake

• Affected by biological, psychological, social, and developmental processes

125 kcal

95 kcal 152 kcal

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

Relationship between physical activity & weight changes

Sitting 90 kcal (1.0 MET)

Standing 110 kcal (1.2 MET)

Watering lawn 136 kcal (1.5 MET)

Mild stretching 228 kcal (2.5 MET)

Bicycling (<10mph) 364 kcal (4.0 MET)

Bicycling (stationary) 500 kcal (5.5 MET)

Weightlifting 546 kcal (6.0 MET)

Aerobic 590 kcal (6.5 MET)

Swimming, moderate 636 kcal (7.0 MET)

Running (5mph, 12 min/mi)

728 kcal (8.0 MET)

Circuit training 728 kcal (8.0 MET)

Swimming, vigorous 908 kcal (10.0 MET)

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

Table 21-1 Kcal expended per hour across activities for a 90 kg (198 lb) person

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

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

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

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

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 reduced calories and

reports of >1 hr of moderate-intensity activity daily

• Decreases in activity associated with weight regain

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

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

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

Measurement of physical activity

• Subjective/Self-report methods – inexpensive, frequently used in epidemiological and intervention studies• Diaries• Interviews• Questionnaires

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

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

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

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

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

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

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

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

Questions?

Activity: Based on the following motivational quotes, what do you think are some of the biggest misconceptions

about physical activity and weight loss?

Thank you!