Obesity: Definitions, Fat Distribution, and Health Risks in Biology

Metabolic conditions

Adversely alter chemical reactions in cells that provide energy for bodily processes

What is obesity

A complex chronic health condition characterised by excessive or dysfunctional adipose tissue that impairs health and wellbeing

What is the main tissue increased in obesity

Adipose tissue

Why is fat distribution important in obesity

Because where fat is stored affects metabolic risk and health outcomes

What is android fat distribution

Apple-shaped body with more visceral fat around the abdomen

What is gynoid fat distribution

Pear-shaped body with more fat stored around the hips and thighs

What are adipocytes

Fat cells that store triglycerides

What do adipocytes contain

Triglycerides along with vascular, lymphatic and nervous tissue

Where is fat ideally stored

Subcutaneously (under the skin) rather than viscerally

What is the normal fat distribution ratio in the body

Approximately 85% subcutaneous and 15% visceral

What is a healthy body fat percentage for women

21-24%

What is a healthy body fat percentage for men

14-17%

What are the functions of adipose tissue

Energy storage and release, endocrine function, insulation, and immune involvement

How does adipose tissue function as an endocrine organ

It helps regulate appetite and metabolic processes

What causes obesity at a basic physiological level

An imbalance between energy consumption and energy expenditure

What BMI classifies obesity

BMI greater than 30

Why is BMI limited as a diagnostic tool

It does not differentiate between fat and lean mass or indicate fat distribution

Can BMI overestimate or underestimate obesity

Yes

What is pre-clinical obesity

Excess adiposity with increased risk of developing clinical obesity but no functional impairment yet

What is clinical obesity

Chronic systemic illness with altered function of tissues, organs, or the whole individual

Can obesity go into remission

Yes, it can move from clinical obesity to pre-clinical obesity

What are three methods to assess excess body fat

BMI with body size measures, at least two body size measurements, or direct body fat measurement such as DEXA

What waist circumference indicates increased risk in men

Greater than 102 cm

What waist circumference indicates increased risk in women

Greater than 88 cm

What waist-to-hip ratio indicates increased risk in men

Greater than 0.90

What waist-to-hip ratio indicates increased risk in women

Greater than 0.85

What waist-to-height ratio indicates increased risk for both sexes

Greater than 0.50

Why are ethnic-specific cut-offs important

Because body composition and risk profiles differ between ethnic groups

What defines dysfunction in obesity

Altered tissue or organ function and/or limitation in day-to-day activities

Give examples of dysfunction in obesity

Breathlessness with activity, joint pain, metabolic abnormalities, reduced daily function

What are major determinants of obesity

Genetics, physical inactivity, unhealthy diet, ethnicity, medication, stress, poor sleep

What percentage of people with obesity have a genetic predisposition

Approximately 70%

How do environmental factors interact with genetics in obesity

They can significantly increase obesity risk

What socioeconomic factors influence obesity risk

Poverty, poor employment, high cost of healthy food, low socioeconomic status, poor education

What happens to excess energy in the body

It is converted into triglycerides and stored in adipocytes

What brain structure regulates appetite

The hypothalamus

Which organs influence appetite regulation along with the brain

The gut, adipose tissue, and pancreas

What is adipocyte hyperplasia

An increase in the number of fat cells

What is adipocyte hypertrophy

An increase in the size of fat cells

Where is visceral fat stored

Around internal organs in the abdominal cavity

Why is visceral fat more harmful

It is strongly associated with metabolic dysfunction

What is ectopic fat

Fat stored in organs not designed for fat storage

Where can ectopic fat accumulate

Skeletal muscle, heart, liver, and pancreas

What does ectopic fat cause

Organ dysfunction

What inflammatory state is associated with obesity

Low-grade chronic inflammation

What happens to free fatty acids in obesity

They increase

What is insulin resistance

When body cells do not respond properly to insulin

What happens to blood glucose in insulin resistance

It increases in the bloodstream

What happens to insulin production during insulin resistance

It increases

What mechanical dysfunction can result from excess adipose tissue

Excess weight load and compression of tissues

What skin-related issues can occur in clinical obesity

Skin fold irritation, rash, and infection

How does obesity affect exercise tolerance

Causes breathlessness and fatigue leading to reduced tolerance

What lipid abnormalities are seen in obesity

Elevated triglycerides and reduced HDL

What plasma glucose range indicates pre-diabetes

6.1-6.9 mmol/L

What plasma glucose level is considered normal

≤ 6.0 mmol/L

What HbA1c range indicates pre-diabetes

41-49 mmol/mol

What HbA1c level is considered normal

≤ 40 mmol/mol

What are three major progression areas of obesity complications

Mental health, mechanical dysfunction, metabolic dysfunction