Year 2 Nutrition Unit I: Energy Balance & Obesity

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Questions and Answers

What is the respiratory quotient (RQ) for a mixed diet?

0.8 (correct)

1.0

0.9

0.7

What factor does not affect the Basal Metabolic Rate (BMR)?

Altitude (correct)

Sex

Weight

Age

Which macronutrient requires the most oxygen for oxidation?

Sugars

Carbohydrates

Fats (correct)

Proteins

In individuals with diabetes, what change occurs in the RQ?

RQ decreases below normal Signup and view all the answers

What is the minimum energy requirement for the body at rest called?

Basal Metabolic Rate (BMR) Signup and view all the answers

What effect does leptin have on feeding behavior?

Inhibits feeding with less intensity and short duration Signup and view all the answers

Which neuropeptides are considered orexigenic?

AgRP and NPY Signup and view all the answers

Which of the following peptides is NOT associated with increasing appetite?

Corticotropin-releasing hormone (CRH) Signup and view all the answers

Where are first-order neurons that produce orexigenic neuropeptides located?

Arcuate nucleus Signup and view all the answers

What is the role of cholecystokinin (CCK) in feeding regulation?

Decreases appetite Signup and view all the answers

What does the calorimetry process measure in terms of food?

The amount of energy released when food is metabolized Signup and view all the answers

What is the specific heat capacity of water as stated in the content?

4.2 J/gºC Signup and view all the answers

What is defined as 1 dietary calorie?

The amount of heat required to raise 1 kg of water by 1°C Signup and view all the answers

The respiratory quotient (RQ) is calculated using which formula?

RQ = Volume CO2 produced / Volume O2 consumed Signup and view all the answers

What does a higher respiratory quotient (RQ) value indicate?

More carbohydrates are being metabolized Signup and view all the answers

What does the calorimeter directly measure during the combustion of food?

The heat released Signup and view all the answers

Which of the following best explains the relationship between food combustion and metabolism?

The heat released from food combustion is equivalent to that during metabolism Signup and view all the answers

What is the main purpose of measuring the respiratory quotient (RQ)?

To identify the type of macronutrients being oxidized Signup and view all the answers

What is the primary action of Leptin in the body?

Decrease hunger and increase energy expenditure Signup and view all the answers

Which orexigenic peptide is identified as the most potent in stimulating food intake?

Neuropeptide Y (NPY) Signup and view all the answers

What initiates the signaling for hunger when fat stores are low?

Decreased leptin signaling Signup and view all the answers

Which neurons does Leptin modulate to exert its anorexigenic effects?

AgRP and POMC neurons Signup and view all the answers

Which gene is involved in the production of the leptin hormone?

ob gene Signup and view all the answers

What is the effect of increased leptin levels in the body?

Both B and C Signup and view all the answers

What role does Neuropeptide Y (NPY) play in energy regulation?

It is a potent appetite stimulant Signup and view all the answers

Which of the following peptides is secreted from the lateral hypothalamus and is orexigenic?

Melanin-concentrating hormone (MCH) Signup and view all the answers

What is a characteristic feature of ob/ob mice?

Mutation of the gene encoding leptin Signup and view all the answers

What contributes to leptin resistance in obese individuals?

Change in leptin receptor signaling Signup and view all the answers

Which treatment directly targets the feeding centers in the brain?

Amphetamines Signup and view all the answers

What is one method of non-surgical treatment for obesity that acts on the gut?

Orlistat Signup and view all the answers

What is the primary function of sodium-glucose transporter 2 (SGLT2) inhibitors?

Prevent glucose and water reabsorption Signup and view all the answers

What type of surgical procedure involves the removal of a large part of the stomach?

Vertical sleeve gastrectomy Signup and view all the answers

Which drug is known to decrease hunger by stimulating POMC neurons?

Synthetic GLP-1 agonists Signup and view all the answers

Inanition is best defined as what?

The opposite of obesity Signup and view all the answers

What happens to leptin levels when adipose stores are enlarged?

Leptin levels increase significantly Signup and view all the answers

What is one potential outcome of dysregulation in leptin expression?

Development of obesity Signup and view all the answers

Study Notes

Energy Available in Foods

Nutrients that provide energy include carbohydrates, proteins, and fats.
Stored chemical energy is released through cellular respiration.

Determining Energy Content of Food

Calorimetry measures energy through the combustion of food, producing heat that raises water temperature.
Specific heat of water: 4.2 J or 1 calorie (cal) raises 1 g of water by 1ºC.
1 dietary calorie (Cal) = 1000 calories (1 kcal).
Energy obtained from food combustion parallels energy utilized by the body during metabolism.

Respiratory Quotient (RQ)

RQ = Volume of CO2 produced / Volume of O2 consumed indicates which macronutrient is oxidized.
Carbohydrates: RQ = 1 (complete oxidation).
Fats: RQ = 0.7 (more O2 required for oxidation).
Proteins: RQ = 0.8.
Mixed diet RQ approximates to 0.8; RQ decreases in conditions like Diabetes Mellitus.

Basal Metabolic Rate (BMR)

BMR represents minimum energy needed for physiological functions at rest (12-14 hrs post-meal).
Average BMR: 2000 kcal/day; expressed as Cal/m²/hr.
Factors affecting BMR include height, weight, surface area, sex, age, muscular exertion, and environmental temperature.

Hypothalamic Networks in Feeding Regulation

Neuropeptidergic networks in the arcuate nucleus regulate appetite.
Orexigenic (hunger-inducing) neuropeptides: Agouti-related protein (AgRP) and Neuropeptide Y (NPY).
Anorexigenic (appetite-suppressing) neuropeptides: Pro-opiomelanocortin (POMC) and Cocaine-and-amphetamine-regulated transcript (CART).
Hypothalamic second-order neurons produce orexigenic peptides (orexin) or anorexigenic factors (oxytocin, TRH, CRH).

Influential Neurotransmitters & Hormones

Anorexigenic: α-MSH, Leptin, Serotonin, Insulin, CCK, CRH.
Orexigenic: NPY, AgRP, MCH, Orexins, Endorphins, Cortisol, Ghrelin.
NPY is the most potent orexigenic peptide, activated by decreased leptin levels.

Role of Leptin in Energy Regulation

Leptin is a peptide hormone from white adipose tissue signaling energy storage levels.
Low leptin indicates reduced fat stores, promoting hunger and energy conservation; high leptin signals increased energy expenditure and decreased hunger.
Genes involved: ob gene (leptin production) and db gene (leptin receptor signaling).

Leptin and Obesity

Obesity leads to leptin desensitization; weight gain is linked to leptin resistance.
Leptin resistance causes include disrupted receptor signaling, altered leptin production, and impaired transportation across the blood-brain barrier.
Mouse models: ob/ob mice (leptin gene mutation) and db/db mice (leptin receptor mutation).

Treatment of Obesity

Pharmacological:
- Amphetamines to inhibit feeding.
- Bupropion (Dopamine and NE reuptake inhibitor) stimulates POMC neurons for satiety.
- GLP-1 agonists.
- SGLT2 inhibitors prevent renal glucose reabsorption.
- Orlistat reduces lipid absorption (lipase inhibitor).
Surgical options:
- Gastric bypass, vertical sleeve gastrectomy, and gastric banding.

Inanition, Anorexia, and Cachexia

Inanition represents the extreme opposite of obesity, indicating a state of starvation or severe weight loss.

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Description

This quiz covers the regulation of energy balance, food intake, and body weight with a focus on obesity. It explores concepts such as energy yielding nutrients and the method of calorimetry for determining energy content in foods. Test your understanding of these vital nutrition principles.