Chapter 20- Weight Management

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Prevalence of Obesity Among American Adults

Canadian Community Health Survey BMI ≥ 30 kg/m2

obesity

Characterized by excessive fat mass

Causally linked to adverse health outcomes

Labeled as a disease in 2013
• Intended to decrease weight bias and stigma

defining obesity

BMI often used even though it does not directly measure
body fat

BMI ≥30 kg · m−2 considered obese
• Grade 1 obesity: 30.0 to 34.9 kg · m−2
• Grade 2 obesity: 35.0 to 39.9 kg · m−2
• Grade 3 (extreme) obesity: 40 kg · m−2 or higher

Waist circumference is used as a screen for obesity:
• ≥102 centimeters (40 inches) for men
• ≥88 centimeters (35 inches) for women

etiology of obesity

Obesity is a complex, multifactorial disease, with many
factors contributing to its development.

Positive caloric balance leads to increased body weight

genetic, lifestyle, and environmental factors

etiology of obesity- genetics

Monogenic or polygenic

Inheritance responsible for 40% to 70% of the interindividual
variation in obesity

Approximately 25% of variance in percent body fat attributable to
genetics

Even with genetic predisposition, great capacity on the part of the individual to affect body weight and fat (e.g., twin studies)

etiology of obesity- lifestyle and environment

Energy intake
• Increases over time

Energy expenditure
• Includes basal metabolic rate, thermic effect of food, and PA
• Decrease in occupational energy expenditure
• Relationship between low levels of physical activity and increased likelihood of weight gain and development of obesity

weight loss goals

Target a loss of 1 to 2 pounds (0.45 to 0.9 kilograms) per week.

General guidelines recommend a calorie deficit of 3,500 to 7,000 kcal per week.

NOTE: Energy expenditure is a dynamic process; 3,500 kcal = 1
pound is an estimate rather than a rule.

weight loss: PA

Standard testing modes and protocols individualized based
on fitness, ambulatory capacity, and current PA

Important to have a comfortable and safe environment

Dose–response relationship with increasing levels of
physical activity, resulting in greater weight loss

General relationship between physical activity and weight
loss:
• Physical activity >150 minutes per week: modest weight loss of ~2 to 3 kilograms
• Physical activity >225 to 420 minutes per week: weight loss of 5 to 7.5 kilograms

Resistance training also important
• May maintain or increase lean mass

Exercise is also important for weight-loss maintenance.
• ACSM recommends >250 minutes per week of moderate-intensity PA

national weight control registry

This source provides information on the habits of adults
who successfully lose weight and maintain weight loss.
• Over 85% used exercise.
• A common approach involved a diet low in total calories and low
in fat.
• Weight was monitored frequently.
• Most exercised about 1 hour per day (80% used walking).

weight loss: dietary aspects

Helpful to know the number of calories needed to sustain current body weight

Estimate daily caloric need:
• Resting metabolic rate (RMR)
• Thermic effect of food
• Energy expended in daily activities

contributors to daily caloric need

calculating daily energy needs

Formulas exist to estimate daily caloric needs.

Equations are based on the following factors:
• RMR is proportional to body size.
• RMR decreases with age.
• Muscle is more metabolically active than fat.

Additional equations exist when fat-free mass (FFM) is known:

RMR (kcal · day−1) = 370 + (21.6 × FFM in kg)

Why is sex unimportant in an equation such as this?

dietary changes

Focus on healthy patterns.

Core foods to eat:
• All types of vegetables
• Fruits (especially raw)
• Grains (at least half of which are whole grains)
• Dairy (if tolerated)
• Protein foods (animal- and plant-based sources)
• Oils at appropriate calorie levels

scope of practice

Fitness professionals are not Registered Dietitians, meaning they should not be providing medical nutrition therapy to clients.

Fitness professionals should only provide information based on established nutrition guidelines, such as the 2020-2025 Dietary Guidelines for Americans.

Pharmacological and Surgical Weight Management Options

Nutrient-stimulated hormone therapies have been found to be effective for weight loss (e.g., GLP-1RA).

Bariatric surgery may be an option for individuals with extreme obesity.

Exercise programming is recommended following recovery from surgery; diet and exercise should be overseen by medical professionals.

gaining weight

Focus on accumulating FFM.

Add resistance training to the exercise routine.

Ensure there is no other underlying condition causing weight loss or struggles with gaining weight

tips to increase weight over time

Increase caloric intake by 200 to 1,000 kcal · day−1 by increasing meal size, number of meals, or number of between-meal snacks.

Add resistance training to daily routine.

When training intensely, make sure to consume 1.5 grams of protein each day for each kilogram of body weight.

anorexia nervosa

A preoccupation with body weight that leads to self starvation

Criteria:
• Restriction of energy intake relative to requirements, leading to significantly low body weight
• Intense fear of gaining weight or of becoming fat, or persistent behavior that interferes with weight gain, despite being at a very low weight
• Disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight or shape on self-
evaluation, or persistent lack of recognition of the seriousness of the current low body weight

bulimia nervosa

Characterized by recurrent episodes of binge eating and
recurrent inappropriate compensatory behaviors to prevent weight gain

Diagnostic criteria: must have engaged in behavior at least once
per week for 3 months

binge eating disorder

Characterized by consuming large amounts of food in a
short time

Not associated with purging

Diagnostic criteria: must engage in binging at least once per week for 3 months

disorder eating

A subclinical condition of unhealthy eating patterns

May lead to a clinical eating disorder

Important for fitness professionals to be aware of signs of
disordered eating