Nutrition 202 - Module 7/Metabolic Pathways

Taught by Christian Lynch @ Texas A&M

What is the relationship between kcals consumed and kcals expended for weight maintenance?

Kcals consumed = kcals expended

What is the relationship between kcals consumed and kcals expended for weight loss?

Kcals consumed < kcals expended

What is the relationship between kcals consumed and kcals expended for weight gain?

Kcals consumed > kcals expended

What are some of the largest sources of added sugar in the diet?

Sugar-sweetened beverages (SSB)

In what 3 ways are calories expended?

1. Resting energy expenditure (REE)

2. Physical activity

3. Thermic effect of food (TEF)

What is total energy expenditure?

The combination of calories burned from REE, physical activity, and TEF

Basal metabolic rate (BMR)

Energy metabolism that occurs after waking up or at least 12 hours after the last meal

What functions make up BMR?

Involuntary life-sustaining functions (e.g. breathing, blood circulation, digestion)

Where are most of our calories burned?

During REE, especially when sleeping

Physical activity

Energy expenditure through voluntary physical effort

Exercise activated thermogenesis

Calories that are burned during moderate to intense activity

Non-exercise activated thermogenesis

Calories that are burned during light activity

Thermic effect of food (TEF)

The process of burning calories as you digest, absorb, transport, store, and metabolize food

What percentage of calories consumed from a meal does your body burn?

10%

What is the thermic effect of protein?

30%

How do you calculate TEF from a meal?

Calories from the meal - 10% of the calories from the feel = calories you actually get after TEF

What is the BMR for women?

665.1 + (9.563 x weight in kg) + (1.85 x height in cm) - (4.676 x age)

What is the BMR for men?

65.1 + (13.75 x weight in kg) + (5.003 x height in cm) - (6.775 x age)

Body mass index (BMI)

A measure of weight relative to height

What is the formula for BMI?

Weight in kg/(height in meters)²

Is BMI a good metric for a population?

Yes

Is BMI a good metric for an individual?

No, it depends

If your BMI is under 18.5, you are __

underweight

If your BMI is between 18.5 and 24.9, you are at __

normal body weight

If your BMI is between 25 and 29.5, you are __

overweight

If your BMI is over 30, you are __

obese

What is the relationship between BMI and mortality?

As BMI increases, your mortality increases. However, there is also an increased risk of mortality with being underweight.

What are some consequences of being obese?

Risk for heart disease, hypertension, type 2 diabetes, stroke, gallbladder disease

What are some consequences of being underweight?

Decreased overall energy, respiratory complications, heart irregularities, infertility, delayed wound healing, weakened immune system, osteoporosis

Osteoporosis

A condition associated with decreased bone mass and bone density

What groups of people are at greater risk of getting osteoporosis?

Older people, women, underweight people, tobacco users, people who aren’t physically active

What hormones drive bone mineral deposition?

Sex hormones

What makes up your total body mass?

Lean tissue mass + fat mass + water

Essential fat

Fat required for normal physiological functions

Where is storage fat located?

In adipose tissue, in tissue under the skin (aka subcutaneous), and around essential organs

Why does body fat usually increase with age?

Less physical activity

Gynoid pattern

Fat that is located over muscle and under the skin at the hips and thighs

What fat makes up the gynoid pattern?

Subcutaneous fat

What is your body shaped like if you have a gynoid pattern?

A pear

Android pattern

Body fat is stored under the abdominal muscle around the internal organs

What fat makes up the android pattern?

Visceral fat

What is your body shaped like if you have an android pattern?

An apple

What receptors cause fat to be stored in the stomach?

Adrenergic receptors

Obesity is affected by what factors?

Physiological, psychological, lifestyle behaviors, social and economic

What factor mostly affects obesity?

Psychological

Set point theory

The theory that the body is programmed to gravitate toward a certain weight

How does your body ensure that you maintain a stable weight?

Your metabolism may adjust upward or downward to ensure that weight is neither gained nor lost

When a person gains weight in the form of fat, what happens to the number and size of adipocytes?

Both the number and size of adipocytes increase

Hypertrophy

The increase of cells’ size

Hyperplusia

The increase of the number of cells

Atrophy

The decrease of cells’ size

Where are G-cells located?

In the stomach

G-cells function

They secrete gastrin

Gastrin function

It encourages the stomach to contract, which then stimulates parietal cells to secrete HCl

Where are I-cells located?

In the duodenum

I-cells function

They secrete CCK (cholecystokinin)

CCK function

It stimulates the gallbladder to release bile into the small intestine and stimulates the pancreas to release pancreatic amylase, lipase, and protease

Where are S-cells located?

In the duodenum

S-cells function

They secrete secretin

Secretin function

It stimulates the pancreas to secrete alkaline bicarbonate

Where are L-cells located?

In the duodenum

L-cells function

They secrete GLP-1 and peptide YY

GLP-1 function

Increases insulin secretion and delays gastric emptying

Peptide YY

Promotes the feeling of satiety in the brain

Leptin

Hormone released by fat cells to signal to the brain that the body has had enough to eat

Which cells secrete leptin?

Adipocytes

What do increased levels of leptin result in?

Increased energy expenditure and a decrease in food intake

What do decreased levels of leptin result in?

Decreased energy expenditure and an increase in food intake

What 3 hormones are associated with satiety?

GLP-1, peptide YY, and leptin (primary)

What 2 hormones are associated with hunger?

Neuropeptide Y, ghrelin (primary)

Hunger

The physiological need to eat

What can hunger be triggered by?

Low blood sugar and low glycogen

Appetite

The psychological desire to eat

What can appetite be triggered by?

The sight or smell of food

Neuropeptide Y

Neurotransmitter that increases food intake and blood glucose levels, promotes the storage of energy in fat cells

Ghrelin

A hunger-stimulating hormone produced by cells that line the stomach when it is empty

What people are candidates for weight loss surgery?

People whose BMI is > 40 kg/m² and people whose BMI is > 35 kg/m² with health conditions

Vertical sleeve gastrectomy

Surgical procedure in which part of the stomach is removed

Vertical banded gastroplasty

Surgical procedure in which bonds and staples are used to create a small stomach pouch

Adjustable gastric band procedure

Adjustable band fits around lower esophageal sphincter

Gastric bypass

Small pouch created from stomach so food can bypass, results in malabsorption of nutrients

Substrate

Anything that can be acted upon by an enzyme

Substrate level phosphorylation

Metabolic process where a phosphate is transferred to a high-energy substrate (in this case, usually an active form of a B vitamin) to ADP, which forms ATP

Oxidative phosphorylation

Metabolic process in which nutrients are oxidized to produce ATP

Oxidative decarboxylation

Produce CO2

Vitamin B1

Thiamin

Active form of vitamin B1

TPP

Vitamin B2

Riboflavin

Active forms of vitamin B2

FADH, FMN

Vitamin B3

Niacin

Active form of vitamin B3

NADH

Where does glycolysis occur?

Cytosol

In what state does glycolysis occur?

A fed state

When does glycolysis occur?

As soon as glucose goes inside a cell

What kind of process is glycolysis?

Anaerobic

What kind of phosphorylation occurs in glycolysis?

Substrate level phosphorylation

What is the starting reactant in glycolysis?

Glucose (C6H12O6)

What is the final product of glycolysis?

2 pyruvate

What enzyme determines the rate of glycolysis?

Phosphofructokinase

What active form of B vitamin is present in glycolysis?

NADH (Vitamin B3)