Week 2 lecture - Obesity

Question 1

Waist circumference

Answer 1

Beyond BMI, waist circumference gives an indication of central obesity (more precisely linked to cardiometabolic risk)

Question 2

BMI limitations

Answer 2

• no info on body composition
• lean or fat mass?
• distribution of fat

Question 3

BMI cut-off points:

Answer 3

Underweight = < 18.5 kg/m2
Healthy weight = 18.5-24.9 kg/m2
Overweight = 25-29.9 kg/m2
Obese = 30-34.9 kg/m2
very obese = > 35 kg/m2

Question 4

Waist circumference - health categories

Answer 4

Low risk: men = <94cm / women<80cm
High risk: men = 94-102cm / women = 80-88cm
Very high risk: men = >120cm / women = >88cm

Question 5

Metabolically healthy obesity

Answer 5

Obese but with fewer cardiometabolic risk factors - better insulin sensitivity, stable BP…

Question 6

Visceral fat

Answer 6

Located deep within the abdomen, surrounding the organs like the liver, intestines and stomach.
A.K.A intra-abdominal fat
Dangerous to health

Question 7

Subcutaneous fat

Answer 7

Located just under the skin
fat that collects around the hips, butt, thighs and belly.
enables excess energy to be stored safely

Question 8

Obesity causes mechanical stress

Answer 8

Physically carrying excess weight can lead to: osteoarthritis, obstructive sleep apnea (fat compresses neck leading to hypoxia)

Question 9

Issues with adiposity

Answer 9

Hypertension - renal compression (Pages Kidney) can increase retention of sodium and water due to physical compression of kidney.
As fat cells become bigger they get stressed (induce a stress response) - recruit immune cells - spit out cytokines into circulation - inflammatory response.
Fat is an endocrine organ - when stressed they excrete adipokines that have a negative impact on metabolism - insulin resistance + diabetes - exaggerated lipolysis - circulating FAs increase - lead to NAFL

Question 10

VLVL cholelstrol

Answer 10

Lipid levels increases which contributes to atherosclerosis and heart disease

Question 11

Adipose tissue is an endocrine organ

Answer 11

As adipocytes get bigger they become hypoxic - cant get blood supply and nutrients they need - causes a stress response and the recruitment of immune cells e.g., monocytes

Question 12

Weight gain leads to….

Answer 12

• Adipose tissue inflammation + insulin resistance
• oxidative stress, ER stress, endothelial damage, more circulating FFAs, adipocyte necrosis
• macrophage recruitment
• IL-6, TNF-a, JNK, IL-1b, TLRs release
• pre-adipocytes can become adipocytes (they are endothelial cells (cells that store fat))

Question 13

Genes Vs Environment

Answer 13

• Adoption studies: identical twins concordance rates are higher than non-identical twins
• Monogenic obesity (single gene defects)- e.g., leptin deficiency affects appetite sensors in the brain - will cause obesity
• Polygenic obesity - combination of genes that link to obesity related traits
• Environment: Industrialisation, mechanisation, transport, leisure, work, diet

Question 14

Surgery

Answer 14

• BMI > 40 or 35 with co-morbidities
• Bariatric surgery: reduces stomach size and reroutes intestines e.g., gastric bypass

Question 15

Ozempic

Answer 15

• GLP-1 based therapy: mimics the action of a drug that is produced in the intestines
• hormone: goes to the hypothalamus and supresses appetite
• scientists have cloned the GLP-1 molecule to make is circulate in the body for longer
• can cause 20-25% weight loss
• Ozempic is 1.8mG
• Wegovy is 2.4mG

Question 16

what % weight loss is clinically signifcant?

Answer 16

5%

Question 17

Limitations of PA epidemiology studies

Answer 17

Don’t measure diet … do people who are more active also consume a healthier diet?
High BMI could make people less active - biodirectionality

Question 18

Nurses health study prospective data:

Answer 18

• Those who did the least PA over the course of 20 years were more likely to gain weight
• Split people into quartiles based on how many single nucleotide polymorphisms relating to obesity they had. When people did low levels of PA the genes did have an impact (put on more weight) but in the high level of PA, the genes effect was nullified.
• High levels of PA protect against genetic predisposition – reduce impact of your genetic risk

Question 19

PA is not good at causing weight loss

Answer 19

• Takes time and effort
• people get injured
• Takes longer to expend energy than consume it
• Energy intake is 100% controllable / expenditure is ~20% controllable
• The majority of individuals who lose weight regain it in less than 1 year
• easier to induce negative energy balance through dietary changes than exercise

Question 20

Type of exercise

Answer 20

Aerobic training - Aerobic training reduces body weight by approximately 2 to 3kg on average compared to controls without training and without dietary intervention and by 1kg compared to resistance training alone, in groups of adults with overweight or obesity. – Oppert et al 2021
- Aerobic training and HIIT lead to similar weight and fat loss in groups of obese adults, as long as energy expenditure is the same (Oppert et al 2021)

Question 21

The only study that has shown that PA can be good for maintaining weight loss (Lundgren et al 2021)

Answer 21

• Very strong randomised control trail
• Ppts lost 13.1kg (12%) body weight in the 8 week run-in
• Placebo: regained approximately half of lost weight (6.1kg) by 52-weeks
• Liraglutide (weight-loss drug) and exercise (singular) maintained lost weight at 52-weeks
• Combination of exercise and liraglutide facilitated weight loss maintenance better than exercise alone or liraglutide alone

Question 22

Lecture take home messages

Answer 22

• Obesity impairs health and longevity via metabolic & physical mechanisms
• Epidemiological evidence suggests that more active individuals gain less weight over time
• Experimental data shows that exercise training can provoke weight loss if the volume is high and diet is controlled
• Recent experimental data demonstrates that exercise training can support weight loss maintenance