Obesity and Weight Management

Definition of Obesity
Obesity is a chronic lifelong condition that is the result of an environment of caloric abundance and relative physical inactivity modulated by a susceptible genotype.
Waist Circumference Measure
•Waist circumference is the most practical tool to evaluate a patient’s abdominal fat.
-Abdominal fat is an independent risk predictor when BMI is not markedly increased or readily calculated.
Diagnostic BMI Ranges
– Underweight: below 18.5
– Normal: 18.5 – 25
– Overweight: 25 – 30
– Obese: above 30
Diagnostic Waist Circumference Measures
– Men: greater than 40 inches is unhealthy
– Women: greater than 35 inches is unhealthy
BMI in Children
•BMI ranges are also used for children when determining whether they are overweight or obese
•BMI for children and teens take into account normal differences in body fat between boys and girls and differences in body fat at various ages.
Diagnostic BMI Ranges in Children
– Underweight: below 5%
– Normal: 5% – 84%
– Overweight: 85% – 94%
– Obese: above 94%
Percentage of US Citizens in Weight Categories
– 36% were at a healthy weight
– 34% were overweight but not obese
– 28% were obese
– 41% of men are overweight and 28% of women
Morbidity and Mortality of Obesity Statistics
-Obesity and physical inactivity are risk factors in more than 20 chronic diseases, including type 2 diabetes, heart disease, and some forms of cancer
-Individuals who are obese have a 10- to 50-percent increased risk of death from all causes, compared with healthy weight individuals (BMI 18.5 to 24.9).
-112,000 excess deaths are due to CVD causes
-15,000 excess deaths are due to cancer
-35,00 excess deaths are due to non-CVD causes
Oklahoma’s Rank in Obesity
Oklahoma has 10th highest overweight percentage and 5th highest obese percentage
Oklahoma’s Rank in Diabetes, Hypertension, and Inactivity
– 6th in diabetes
– 6th in hypertension
– 3rd in physical inactivity
Amount of US Children who are Overweight and Obese
Approximately 25 million US children are overweight or obese.
– 16.3% of OK high school students are overweight
– 16.7% of OK high school students are obese
Direct Costs of Childhood Obesity
Childhood obesity alone is responsible for $14.1 billion in direct costs.
Current Medical Costs of Obesity
Current medical costs for obesity range between $147 and $210 billion a year.
Cost of Major Cardiovascular Diseases
The estimated direct and indirect cost of major cardiovascular diseases totals $444 billion.
Total Cost of Diabetes
The total estimated cost for diabetes is $174 billion.
Homeostasis and how it Regulates Energy Balance
• Homeostasis: The property of a living organism that allows it to regulate its internal environment so as to maintain a stable, sustainable condition in the face of unstable external conditions
– Energy balance is achieved through the physiological concept of Homeostasis
Homeostasis and the Brain
•Hypothalamus: the section of the brain that integrates neural, hormonal and endocrine signals regulating changes in:
-Feeding/satiety cues
-Energy expenditure
-Sex drive
Neuroendocrine Signals Regarding Energy Homeostasis
Hypothalamus orchestrates neuroendocrine signaling related to energy balance
– Afferent receptors
– CNS-Hypothalamus
– Efferent responses
Afferent Receptors
Neural regulators in peripheral organs (the liver, gut and adipose tissue) sense fuel availability (nutrient sensing). The ventromedial hypothalamus receives information from peripheral signals in the form of hormones related to:
-adiposity (ex: leptin)
-Substrate metabolism (ex: insulin)
-hunger (ex: ghrelin)
-satiety (ex: peptide YY3-36)
Interprets afferent signals and initiates, converts or transfers those signals into efferent responses.
Efferent Responses
To maintain energy set point, the hypothalamus initiates one of the following efferent responses in the form of hormones related to:
-Low energy Stores: Stimulates feeding/inhibits satiety AND stimulates energy storage/inhibits REE and voluntary PA
-High energy stores: Inhibits feeding/stimulates satiety AND inhibits energy storage/stimulates REE and voluntary PA
Metabolic Set Point’s Effect on Energy Balance
•Drastic, short-term changes in energy intake (“dieting”) or expenditure result our energy regulatory system compensating so that our current set point will be maintained.
• Energy restriction:
– Produces a transient hypothyroid- hypometabolic state.
– Associated with adaptive decreases in energy expenditure and energy efficiency
•Excessive Energy expenditure: associated with the same adaptive decreases in energy expenditure and energy efficiency to insure availability of energy for basal function
The Reality of Energy Balance
•The effect of
-temporary changes in energy balance
-Age and Energy Balance
•We are never really in energy balance
•To rely solely on the ideal of energy in and energy out as the key to weight regulation negates:
-the influence of the “new” environment on a very susceptible, cortico-limbic reward system
-The powerful overriding influence non-homeostatic pathways have on the hypothalamus
Definition of BMR
•Definition: the metabolic cost of living when:
-you are awake but relaxed
-in a room at a comfortable temp.
-in a post-absorptive state (12-14 hours after a meal)
Factors that Impact BMR
•Height/weight, body surface area
•Women: pregnancy, menstruation, lactation
•Body temperature
•Recent ingestion of food
•Environmental toxins
• Extreme, prolonged alteration of food intake. (Ex: fasting)
• Muscular activity
• Emotional state
• Sleep (optimal vs depravation)
• Environmental temperature
• Circulating levels of hormones, especially epinephrine and thyroid hormone
Thermic Effect of Food and Impact on BMR
•the process of heat production in organisms through the ingestion, digestion and storage of food
•Ingestion of food acutely increases the metabolic rate by 10 to 20% for 2-3 hours after eating
-Lean Protein ~20% increase in EE
-Complex Carbohydrates ~8-10% increase in EE
-Fat ~3-5% increase in EE
Human Evolution to Favor Energy Conservation
-Why we are more efficient than any machine during energy transfer
•Physiological and psychological factors reinforce this. Our current environment exploits this.
•To manipulate energy balance in favor of a decrease in body weight under these conditions, our conscious brain would have to continuously work to override the hard-wired, unconscious function and purpose of our energy system- CONSERVE!!
Evolution of Obtaining Food
•Our primal, reward/emotional and neural processes evolved in a restrictive environment where food was in shorter supply and procuring it often required considerable work. These processes are maladaptive to today’s calorie-abundant environment.
•To maintain energy balance under these circumstances, our conscious brain would have to continually override these unconscious processes.
Memories about Food Sources
•By forming memories and reward expectancies through processes of emotions and learning, this mechanism evolved to engage powerful psychological drives that guaranteed supply with, and ingestion of, beneficial foods from a sparse and often hostile environment.
•Survival foods: foods that prolong fuel availability in the body. Which sources work best?
Hedonic Brain
•Also called the cognitive emotional brain
•Controlled by the cortico-limbic network. Made up of:
-neural cortex (memory, brain function): learn about food sources (foraging) and form memories about good locations for beneficial food sources
-the limbic system (emotions and motivation)
-nucleus accumbens (NAc)- regulated by dopamine: regulates functional food intake and reward expectancies related to food procurement
Memories About Food Sources
•During the consumption phase, the hedonic brain is aided by visual and olfactory cues
-sight, smell, and taste (flavor, palatability)
•These cues cause us to form emotional memories about food and drive us to feed again and again despite the dangers of foraging for and procuring food.
Hypothalamus vs. Cortico-limbic System
-There seems to be crosstalk between the hypothalamus and the cortico-limbic network and the cortico-limbic network usually wins
•The content of “beneficial” foods causes the hedonic brain to override the metabolic brain
Geographic and Sociocultural Influences on Obesity
– Trends in obesity show that the population is becoming more obese each year.
– South/Southeast US is most obese region.
Socioeconomic Status and Obesity
The cost of living in the US is increasing. Many Americans are stressed due to money and their jobs. Other factors:
– Lower level of education
– Affordable health insurance
– Cost and taxes on physical activity (gym, classes, sports, etc.)
Urban Sprawl and Obesity
Growth of large cities and dependence on automobiles has lead to the spreading settlement of surrounding areas with little urban planning. Leads to food deserts, lack of town centers, sidewalks, parks, and recreational areas.
Food Deserts and Food Insecurity and Obesity
A food desert is a low-income census tract where a substantial number or share of residents has low access to a supermarket or large grocery store.
– Poverty rate for that tract is at least 20 percent, or the median family income for the tract does not exceed 80 percent of statewide median family income
– more than 1 mile from a supermarket or large grocery store in urban areas
– more than 10 miles from a supermarket or large grocery store in rural areas
Government Education Policies and Obesity
Reduction in state support of school budgets/shifting of focus towards academic testing to obtain federal funding:
– Dietary Intake: School Lunch Programs
– Physical Activity
Technology and Obesity
Technology has led to an increase in screen time.
– Screen time: the amount of time spent watching television or movies; playing video or computer games; surfing the internet; working on a computer; or using mobile devices to play games/watch videos, etc.
2-Parent Income Households and Obesity
Increases in cost of living have caused an increased need for both parents to work outside the home
– Contributes to the lack of supervision of a child’s activities during after school hours
Food Marketing and Obesity
Greater advertising and marketing of less nutritious foods specifically targeting young viewers.
– Marketing of “fad” diets as quick solutions
– Consumers’ frustration with conflicting/changing nutrition information and advice.
Peripheral Signal of the Vagus Nerve
The presence of food in the stomach stimulates afferent vagal nerve stretch and tension mechanoreceptors. This, in turn triggers
– Chemical/hormonal satiety signals that are sent to the brain
– Digestive factors (peptides and other signals) that are secreted into the stomach, regardless of the cause of the stretch (food or a prophylactic device).
Gut Peptides’ Effect
Other Gut Peptides (PYY, GLP-1) act to:
-optimize the digestive process
-function as short term satiety signals > cease feeding
-function (possibly) as long-term regulators of body weight
Ghrelin: a hormone secreted from the stomach fundus
-stimulates feeding by triggering the hypothalamus to release “feeding” hormones such as NPY and AgRP.
-ghrelin levels rise immediately preceding each meal and decline sharply following the meal.
Leptin is a hormone produced by fat cells that communicates satiety levels and energy availability to the ventromedial hypothalamus while modulating energy expenditure.
– Low leptin levels signal feeding/fat stores are low > inhibit energy expenditure
– High leptin levels signal satiety/fat stores are high > increase energy expenditure
– eat more when fat stores are low and less when fat stores are high
Leptin and Set Point
Weight loss plateau:
↓REE due to lower body mass >
↓ serum leptin due to decrease in size of adipocyte >
↓ weight loss even in a hypocaloric state
CNS Leptin Resistance
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