Obesity

What is obesity characterised by?

• Accumulation of excess body fat

• Influenced by genetic factors favouring food storage

• Decreased exercise

• Increased food intake

How has obesity become a global health concern?

It has become a global epidemic, with more obese people than undernourished worldwide, especially increasing rapidly in children

Which groups are more commonly affected by obesity?

Older individuals, people from poorer societies and less educated groups

What factors contribute to total caloric consumption in adults?

Both quantity and quality of food consumed

How is BMI calculated and classified?

• BMI = weight (kg) / height² (m)

• 20-25: desirable

• 25-30: overweight

• 30-40: obese

• >40: severe obesity

What are the limitations of BMI?

Doesn’t account for age, sex, genetic and ethnic background, or fat distribution and pathophysiology of fat depots

What is android obesity and what are its health risks?

• Fat in the central abdominal area (waist:hip ratio >0.8 women, >1.0 men)

• Associated with hypertension, diabetes, CHD, and insulin resistance

What is gynoid obesity?

• Fat deposited in the lower body (waist:hip ratio <0.8 women, <1.0 men)

• Associated with less metabolic risk

What waist circumference is linked to increased CAD risk?

• >40" in men

• >35" in women

How do fat depots differ biochemically?

Abdominal fat cells are larger, have higher fat turnover, are more hormonally responsive, and their FAs are taken up by the liver, leading to insulin resistance and increased VLDL

What is the stromal vascular fraction in adipose tissue?

It includes fibroblasts, blood vessels, macrophages, immune cells, and nerve tissue alongside adipocytes

What do epigenomic studies reveal about fat?

Subcutaneous fat is generally harmless, while visceral fat promotes inflammation and is associated with diseases like type 2 diabetes and heart disease

What changes occur in fat cells with obesity?

• Increase in number (hyperplasia) and size (hypertrophy)

• White adipocytes can enlarge more than tenfold

What are the two models of body weight regulation?

• "Set point" (stable weight range)

• "Settling point" (fluctuates due to external factors)

Why is calling obesity a “failure of willpower” a misrepresentation?

Obesity involves complex interplay of genetics, environment, socioeconomic factors, and decision-making

What factors contribute to rising obesity rates?

• Genetics

• Epigenetics

• Hormones (e.g. additives)

• Behavioural/environmental factors (like ultra-processed foods)

How does genetics influence obesity?

• Polygenic inheritance, as shown in twin/adoption studies

• Rare monogenic forms exist (e.g., leptin deficiency)

What is leptin's role in fat storage?

Leptin helps maintain fat stores and influences energy balance

What other hormones affect obesity?

• Ghrelin (stimulates appetite)

• CCK (signals satiety)

• Insulin (increases metabolism, reduces intake)

What are key metabolic effects of obesity?

• Dyslipidemia

• Glucose intolerance

• Insulin resistance

• Metabolic syndrome

• Non-Alcoholic Fatty Liver Disease (NAFLD)

What defines the metabolic syndrome?

• Obesity with hypertension

• Insulin resistance

• Low HDL

• High TAGs

• Small dense LDL

• Inflammation

• Oxidative stress

• Reduced fibrinolysis

What causes dyslipidemia in obesity?

Hormone-sensitive lipase increases FAs, which are converted in the liver to TAGs and VLDL, raising serum TAGs and lowering HDL

What is nonalcoholic fatty liver disease (NAFLD)?

TAG deposition in the liver due to obesity, leading to hepatic steatosis and liver complications

What major health risks are linked with obesity?

• Cancer (breast, prostate, colorectal)

• Atherosclerosis

• CHD

• Stroke

• T2DM complications

• Respiratory disease

How does weight change with positive energy balance?

Increases in BMR, cost of digestion, absorption, TAG/glycogen synthesis, and physical activity

What happens in negative energy balance?

Decrease in BMR, digestion, synthesis, and protein turnover. Initial rapid weight loss is mostly water

What methods can be used to lose weight?

• Starvation

• Low-energy diets

• Ketogenic/low-GI/high-fibre diets

• Pharmacological/surgical treatments

• Food substitutes

• Exercise

• Lifelong changes

Which diets are likely ineffective?

• Beverley Hills diet

• Blood group diet

• Cabbage soup

• Hay diet

• Detox diets

• Duvet

• Macrobiotic

• pH

• Zone

• Paleo

• Raw food

• Raw vegan diets

What are GLP-1 agonists and how do they help in obesity?

Drugs mimicking GLP-1, increasing insulin, slowing gastric emptying, increasing satiety, and possibly reducing CVD risk

What is energy balance in obesity?

The difference between energy intake and energy expenditure - more complex than a simple calories in/calories out model

How does BMI correlate with gallstone risk?

Risk increases progressively with BMI

What did the American Cancer Society study find about obesity and premature mortality?

Relative mortality rises with weight for all causes, especially CHD, cancer, diabetes, digestive and cerebrovascular diseases