29. Weight Loss & Dieting

Question 1

Define

Ketogenic diet

Answer 1

a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used mainly to treat hard-to-control epilepsy in children. The diet forces the body to burn fats rather than carbohydrates

Question 2

Define

Weight cycling

Answer 2

also known as yo-yo dieting, refers to the process of losing weight, only to gain it back and repeat the cycle again shortly thereafter

Question 3

Definition

a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used mainly to treat hard-to-control epilepsy in children. The diet forces the body to burn fats rather than carbohydrates

Answer 3

Ketogenic diet

Question 4

Definition

also known as yo-yo dieting, refers to the process of losing weight, only to gain it back and repeat the cycle again shortly thereafter

Answer 4

Weight cycling

Question 5

True or False:

Energy expenditure is only decreased in individuals who lose weight through dieting alone

Answer 5

False

ENERGY EXPENDITURE IS REDUCED FOLLOWING WEIGHT LOSS FROM A NUMBER OF DIFFERENT APPROACHES

Question 6

Which areas of energy expenditure get lowered in individuals who lose weight?

Answer 6

BMR

Adaptive thermogenesis

Question 7

What is the cycle of yoyo dieting (weight cycling)?

Answer 7

Question 8

What have weight cycling studies in mice shown?

Answer 8

Weight cycling:

• increases food intake and reduces feed efficiency (gain weight with fewer calories)
• Reduces energy expenditure
• Causes glucose intolerance and insulin resistance

Question 9

What happens to neuroendocrine levels following weight loss?

Answer 9

Weight loss decreases leptin and insulin but increases ghrelin

Question 10

Explain with regards to gut peptides and ghrelin how dieting can mimic a fasted state

Answer 10

Weight loss lowers levels of the gut pepetides (PYY, amylin and CCK) and increases ghrelin.

As Ghrelin increases, we feel more hungry

As gut peptides decrease, we also feel hungry

Question 11

What happens in the hypothalamus when ghrelin increases and/or gut peptides decrease?

Answer 11

Increased stimulation of AgRP and NPY neurons

Decreased stimulation of POMC neurons

Question 12

Why is adaptive thermogenesis lowered in individuals who lose weight?

Answer 12

Following weight loss, AgRP and NPY neurons are more active

These neurons project to the part of the brain that sympathetically innervate BAT and suppresses them

Causes a decreased thermogenic response

Question 13

What is the key summary of how various endocrine and metabolic adaptations occur to slow or prevent weight loss?

Answer 13

↓ Leptin, satiety gut peptides (PYY, CCK); ↑ Ghrelin

⇩

↓ POMC; ↑ NPY/AgRP

⇩

↑ Hunger; ↓ Thermogenesis and Energy Expenditure

Question 14

What was the ketogenic diet originally developed?

Answer 14

Used to reduce seizure frequency in treatment-resistant epilepsy (reduces by 50%!)

Achieves this by reducing the amount of glutamate and increasing the amount of GABA

Question 15

What is the metabolic basis for effect of ketogenic diets?

Answer 15

• Low carbohydrate
• Increased fatty acid oxidation
• Utilisation of ketones for energy
• Ketones readily cross the BBB so can be used as an energy source by the brain
• Weight loss
• Improved glucose tolerance
• No adverse effect of lipid profile

Question 16

What does a keto diet do to satiety, hunger and desire to eat levels?

Answer 16

↑ Satiety

↓ Hunger

↓ Desire to eat

Question 17

True or False:

Keto diets are a way to avoid the compensatory gut hormone decreases

Answer 17

False

Same consequences as traditional dieting