Body Weight and Its Management
Overweight and Obesity
• Conditions characterized by excessive and unhealthy amounts of body fat
• Result from a complex combination of biological, psychological, environmental, cultural, and socioeconomic factors
• Obesity—a chronic metabolic disease that is extremely difficult to treat
Overweight and Obesity (continued)
• The majority of adult Americans have too much body fat.
• Overweight and obesity are the most common nutritional disorder in the United States.
• These conditions often result from a combination of poor diet and lack of physical activity.
Overweight and Obesity (continued)
• A healthy body is not fat-free.
• Adipose cells store extra energy from food as triglyceride (fat).
• As more excess energy is consumed, fat cells continue to store it as fat and increase in size.
• Under certain conditions, more fat cells can develop.
Defining Overweight and Obese
• Height and weight tables are no longer used to determine whether a person is overweight or obese.
• The body mass index (BMI) is used to determine if a person weighs too much.
• BMI is a ratio of height to weight.– To calculate BMI, multiply weight (lbs) by
705; then divide the number by height in inches squared.
Body Mass Index
– BMIs of less than 18.5 are in the underweight range.
– BMIs of between 18.5 and 24.9 are considered healthy.
– BMIs of 25.0 to 29.9 are within the overweight range.
– BMIs of over 30.0 are in the obese range.– BMIs of 40 or more are referred to as
morbid, extreme, or super obese.
Prevalence of Overweight and Obesity
• In the United States, the prevalence of excess body fat has reached epidemic proportions.– In 1980, almost 50% of adults were
overweight or obese.– By 2004, 66% of adults were too fat.– Nearly 1 in 3 adults were obese.
• American children are growing fatter, too.• The WHO recognizes obesity as a
worldwide health problem (globesity).
Health Risks• Overweight and obese people have higher than
average risks of:– Osteoarthritis– Sleep apnea– Gallbladder disease– Carpal tunnel syndrome – Gout – Hypertension– Diabetes– Metabolic syndrome– Heart disease
Health Risks (continued)
• Certain cancers:– Colon– Breast (menopausal women)– Uterus– Kidney– Esophagus
• Surgery is riskier
• Breathing problems
Health Risks (continued)
• Fertility problems• Gestational diabetes, hypertension during
pregnancy, and giving birth to babies with birth defects
• Interference with daily activities like walking, carrying, kneeling, and stooping
• Psychological depression, particularly among obese women
The Caloric Cost of Living
• The body expends 50% to 70% of calories to fuel vital metabolic activities, including:
– Building and repairing tissues– Breathing – Circulating and filtering blood– Producing and transporting substances– Maintaining body temperature
The Caloric Cost of Living (continued)
• Factors that influence the metabolic rate include:– Genetics– Hormones
• Thyroid hormone– Proportion of muscle to fat– Gender– Age– Exercise
The Caloric Cost of Living (continued)
• Physical Activity– Calories are needed to move skeletal
muscles.• Number of calories used is influenced by:
–Type of activity–Duration–Intensity–Size of person
Energy for Physical Activities
• The amount of energy needed for physical activity depends on the activity, its duration, and intensity.
• Physical activities include:– Sport types of exercise– Movement for daily living– Spontaneous muscular movement
• Health experts recommend that adults perform at least 30 minutes of moderate-intensity physical activity daily.
• Each day, the typical American expends more energy for physical activities associated with daily living than for sport types of activities.
Caloric Cost of Living: TEF
• Energy expended for physical activity and vital energy needs require about 90% of body’s energy use.
• After eating a meal, the body needs a small amount of energy to digest, absorb, and process nutrients from food.
• Thermic effect of food (TEF) accounts for less than 10% of total energy needs.
Energy Balance
• When:– Caloric intake equals caloric output, weight
is maintained.– Caloric intake is more than caloric output,
weight gain occurs.– Caloric intake is less than caloric output,
weight loss occurs.• One pound of fat represents about 3,500
calories.
Body Composition
• Healthy adults consist of:– About 60% water– 6% to 22% protein– 3% minerals– Remaining weight is mostly fat
• Body fat for healthy adults– About one-half of an average person’s fat is
subcutaneous.– “Cellulite” does not exist; it’s the same as
other fat.
Estimating Body Fat
• Hydrostatic weighing (underwater)– Very reliable but not practical or convenient
• Bioelectrical impedance– Uses electrical currents to estimate
percentage of fat– Small device needed but can provide
accurate estimate
Estimating Body Fat (continued)
• Near-Infrared Interactance (“Infrared”)– Infrared light is used to estimate percentage
of fat (through biceps muscle of upper arm)– Often underestimates
• Dual-Energy X-ray Absorptiometry (DEXA)– Measures fat and bone density– Accurate, but expensive– Requires X-ray technician to perform
measurement
Estimating Body Fat (continued)
• Skinfold Thicknesses – “Pinch an inch” method– Practical and less costly than above methods– Reliability of measurements can be
questionable
• Waist Circumference – Determines distribution of fat in abdominal
area– Need flexible measuring tape
Estimating Body Fat (continued)
• Distribution of fat is a more important risk factor than percentage of fat.– “Apple-shapes”
• More fat in the central part of body than below waist
• Greater risk of serious health problems– “Pear-shapes”
• Have excess body fat below waist• Less risk of serious health problems than
when fat is centrally located
Causes of Obesity: Biological Influences
• Genetics– Genes code for:
• Body frame• Fat distribution• Hormones that regulate appetite and
metabolism– Some people have “thrifty metabolisms”
that tend to conserve energy as fat.
Causes of Obesity: Biological Influences (continued)
– According to the set point theory, the level of body fat is genetically preset.
• Hunger is the physiological drive to seek and eat food.
• Appetite is the psychological desire to eat specific foods.
• Satiety is the feeling that enough food has been eaten to relieve hunger and turn off appetite.
Causes of Obesity: Biological Influences (continued)
• The digestive system, brain, and fat cells play important roles in controlling hunger and satiety.
• The composition of the diet can affect body weight.
• Excess calories from carbohydrate, protein, fat, and alcohol can result in weight gain.
–A high-fat diet is associated with overeating and gaining body fat.
Causes of Obesity: Other Influences
• A variety of environmental, social, and psychological factors promote overeating.– Portion sizes have increased.– Certain types of restaurants encourage
overeating.• Fast food and family-style restaurants often
promote “super-sized” portions as bargains.
– Advertising makes food look more appealing.
Causes of Obesity: Other Influences (continued)
– Food availability and convenience, e.g., pizza delivery 24 hours a day
– Tendency to overeat during holidays and family gatherings
– Sedentary lifestyles– Moods
Weight Management
• Balance food intake with energy expenditure.• Avoid fad diets.
– Usually result in temporary weight loss– Promote gimmicks– Often are nutritionally inadequate– Fasting may be dangerous
• Increase physical activity.• Change eating and physical activity habits for
life.
Role of Physical Activity
• Daily exercise helps people lose or maintain weight.
• Exercise for at least 30 minutes a day.
• Physical activities such as walking, jogging, biking, swimming are recommended; choose enjoyable ones.
• People over age 40 should obtain approval of personal physician before beginning a vigorous exercise program.
Other Methods of Weight Control
• Surgical methods– Gastric bypass– Liposuction
• Medications– Appetite suppressants– Fat absorption reduction (small intestine)
Successful Weight Loss Strategies
• Sensible and safe weight loss plans:– Are medically and nutritionally sound– Include practical ways to engage in physical
activity– Are adaptable to one’s psychological and
social needs– Can be followed for a lifetime
Successful Weight Loss Strategies (continued)
• Set realistic weight loss goals.• Emphasize behavior modification.
– Eat nutritiously as well as develop physical activity habits.
• Follow the MyPyramid Plan.• Engage in at least 30 minutes of physical
activity daily.• Seek family or other forms of social support.• Include long-term plan for maintaining new
weight.
Weight Gain
• To gain weight by increasing lean tissue:– Need at least 700–1,000 additional calories
per day– Eat three meals per day plus snacks.– No more than 30% calories from fat.
• Perform muscle-building exercise.• Maintain effort over long term.
Across the Life Span
• Average weight gain during pregnancy is 25 to 35 pounds.– Underweight women can gain more
weight; overweight women can gain a few pounds less than average, but they should gain at least 20 pounds.
• Food restriction and weight loss may be hazardous to developing fetus.
• Lose weight before or after pregnancy.
Across the Life Span (continued)
• Low-calorie or fat-restricted diets are not recommended for children under 2 years of age.
• Overweight children need more physical activity.• Limit time spent engaging in sedentary
activities.• Contrary to conventional wisdom, elderly persons
may enjoy good health and live longer by being overweight and even obese.– Serve as energy source– Can protect from serious internal injuries when
they fall
