Obesity
Obesity, Metabolic Syndrome
Overweight Measures
Definitions:
Overweight:
Defined as being 20% or more over the ideal weight.
Obesity:
Defined as being 30% or more over the ideal weight.
Morbid Obesity:
Defined as being 40% or more over the ideal weight.
Adipose Cells
Adipose tissue can:
Increase in number of cells (hyperplasia) or hypertrophy (size of cells) to increase overall fat mass.
Major Areas of Fat Storage:
Subdermal Tissue (Subcutaneous):
Located just under the skin, contributes to body shape and insulation.
Omentum (Visceral Fat):
Covers intestines and organs, associated with various metabolic issues.
Subcutaneous Fat (SBC) vs. Visceral Fat (VSC)
Risk Levels of Fat Types:
SBC (Subcutaneous Fat):
Considered to have the lowest risk.
VSC (Visceral Fat):
Considered to have moderate to highest risk for health issues.
Obesity Genes
Research into genetic influences on obesity:
A number of gene loci are being studied for their potential role as "obesity genes."
In obese children, 5% exhibit mutations on 2p23 and 18q21.3.
Individuals lacking the leptin gene or with mutations in the leptin receptor gene at 7q31 tend to be obese.
Mutations causing enzyme alterations at 5q15-21 are linked to significant obesity.
Severe obesity is associated with mutations in the adipocyte transcription factor gene at 3p25.
Adipokines
Overview:
Adipocytes (fat cells) are metabolically active and secrete a multitude of substances called adipokines.
Key Adipokines:
Tumor Necrosis Factor Alpha (TNF-alpha)
Interleukin-6 (IL-6)
Angiotensinogen (AGT)
Plasminogen Activator Inhibitor (PAI)
Adiponectin
Leptin
Resistin
Adipokine Functions
Adiponectin:
Enhances cellular sensitivity to insulin.
Exhibits anti-inflammatory effects.
Provides protection against the formation of arteriosclerosis.
Referred to as a "Good" adipokine due to its favorable metabolic effects.
Inverse Relationship with Adiposity:
Individuals with lower adiposity produce greater amounts of adiponectin; higher adiposity results in decreased adiponectin levels.
Leptin
Function:
Increases in fat mass lead to increased production of leptin.
Leptin signals the brain that the body has consumed enough food.
Resistance in Obese Individuals:
Individuals with obesity can develop resistance to leptin, resulting in reduced feelings of satiety after meals.
Works synergistically with adiponectin to enhance cellular sensitivity to insulin, lower triglyceride levels, and inhibit fat accumulation.
Also classified as a "Good" adipokine.
Resistin
Effects on Metabolism:
Resistin is associated with causing insulin resistance.
Contributes to increased hepatic glucose production, elevated triglyceride levels, decreased HDL levels, and endothelial dysfunction, which predispose individuals to early arteriosclerotic lesions.
Referred to as a "Bad" adipokine due to its detrimental metabolic effects.
Angiotensinogen (AGT)
Role in Circulation:
AGT is produced by adipose tissue and contributes to increased vascular tone.
Can lead to hypertension and vascular changes associated with arteriosclerosis.
Considered a "Bad adipokine."
Plasminogen Activator Inhibitor (PAI)
Characteristics:
Secreted by adipose tissue, PAI inhibits tissue plasminogen activator (tPA), which dissolves blood clots.
In obesity, elevated levels of PAI obstruct fibrinolysis, increasing susceptibility to clot formation.
Increased Free Fatty Acids and Organ Damage
Consequences of Excess Fat:
Excess fat leads to the release of increased free fatty acids (FFAs).
A decrease in pancreatic insulin production and potential organ damage can occur as a result.
Increased TNF-alpha and IL-6 levels are also observed, further leading to insulin resistance and dyslipidemia.
Cardiovascular Disease Risk
Increased Fat Cells:
A rising number of fat cells correlates with a heightened risk of cardiovascular disease due to the secretion of adipokines, AGT, and PAI from adipose tissue.
Ghrelin and Appetite Regulation
Ghrelin Overview:
Ghrelin is a peptide secreted by the stomach that stimulates hunger and regulates food intake.
Influences growth hormone secretion and is implicated in numerous metabolic functions.
Potential Dysregulation:
Insensitivity to Growth Hormone Secret Receptor (GHS-R) may occur, along with alterations in blood-brain barrier transfer affecting appetite control.
Interactions:
Links between ghrelin, motivation/reward systems, as well as the regulation of gastric motility and emptying.
Risk Factors for Obesity
Contributing Factors:
Excess calorie intake relative to energy output.
Sedentary behavior.
Socioeconomic status (poverty).
Cultural influences.
Age considerations.
Gender, with females generally at higher risk.
Smoking cessation can lead to weight gain.
Genetic predispositions.
Secondary disorders such as Cushing’s disease can also cause obesity.
Obesity as a Cardiovascular Risk Factor
Waist Measurements:
A waist measurement exceeding 35 inches for women or 40 inches for men is linked with increased cardiovascular disease risk.
Apple-shaped central obesity is particularly concerning.
Recommended Body Fat Percentages
Healthy Body Fat Ranges:
Females are recommended to maintain body fat at 30% or lower.
Males are recommended to maintain body fat at 25% or lower.
Body Mass Index (BMI)
Calculation Methods:
BMI can be calculated using:
Weight in kilograms divided by height in meters squared,
Or by the formula: [Weight in pounds / Height in inches^2] x 703.
BMI Classification:
18.5 to 24.9: considered ideal.
25 to 29.9: classified as overweight.
30 or greater: indicates obesity.
Drug Therapy for Obesity
Indications for Medication:
Drug therapy should be used as an adjunct to diet and exercise.
Indicated for individuals with increased health risks, specifically:
BMI of 30 or greater.
BMI of 27 or greater with additional risk factors.
Should only be initiated after a 6-month trial of diet and exercise.
Limitations:
Medications have limited effectiveness and may lead to weight regain once discontinued, as obesity is categorized as a chronic disease.
FDA-Approved Obesity Drugs
Medications Include:
Orlistat (Xenical):
Mechanism of Action (MOA): Reduces fat absorption.
Two-year weight loss: approximately 19 lbs vs. 12 lbs for placebo.
Adverse effects include black box warning for liver injury and GI symptoms; must be taken with a multivitamin.
Phentermine/Topiramate (Qsymia):
An appetite suppressant combined with anticonvulsant properties.
Naltrexone SR/Bupropion SR (Contrave):
Combination drug affecting appetite and cravings.
Liraglutide (Saxenda):
Administered through daily injection; also used (as Victoza) for Type 2 Diabetes Mellitus (T2DM).
Semaglutide (Rybelsus):
Available as both tablets and weekly injection (brand name Wegovy); affects appetite and glycemic control.
Bariatric Surgery Options
Types of Procedures:
Liposuction:
A surgical procedure to remove subcutaneous fat.
Gastric Bypass:
A procedure that alters the stomach and digestive system to promote weight loss.
Gastric Banding:
Involves placing a band around the stomach to limit food intake.
Metabolic Syndrome
Components of Metabolic Syndrome:
Characterized by insulin resistance, leading to conditions such as Type 2 Diabetes Mellitus, high blood pressure, low HDL cholesterol, and fatty liver disease.
Criteria for Diagnosis (at least 3 out of 5):
Waist circumference (WC):
≥90 cm for males; ≥80 cm for females (specific to Japanese populations).
Triglycerides:
>150 mg/dL.
HDL-C (High-Density Lipoprotein Cholesterol):
<40 mg/dL for males; <50 mg/dL for females.
Blood pressure:
≥130/85 mmHg.
Fasting Plasma Glucose (FPG):
>100 mg/dL or with diagnosis of T2DM.
Implications of Metabolic Syndrome
Referred to as Syndrome X:
This condition increases the risk of heart disease and stroke.
Management strategies include:
Weight loss.
Regular exercise.
Adopting a healthy diet.
Smoking cessation.
Medications for control of blood glucose and lipid levels.