Nutrition: Essential Fatty Acids and Metabolism

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Questions and Answers

What is the primary energy source during mild exercise at 25 percent VO2 max?

Protein

Amino acids

Carbohydrates

Fat (correct)

What limits fat oxidation during high-intensity exercise (≥85 percent VO2 max)?

Increased carbohydrate availability (correct)

High plasma FFA levels

Increased fat mobilization

Greater muscle triglyceride storage

Which hormone stimulates the release of fatty acids from adipose cells to muscle during exercise?

Insulin

Cortisol

Glucagon

Epinephrine (correct)

What happens to free fatty acid (FFA) oxidation as exercise intensity increases?

It decreases Signup and view all the answers

Which factor can inhibit fatty acid oxidation during exercise?

Increased muscle glycogen levels Signup and view all the answers

What is the role of triglycerides stored in muscle cells during exercise?

To serve as a rapid energy source Signup and view all the answers

How does carbohydrate intake affect fat oxidation during exercise?

It decreases fat oxidation Signup and view all the answers

What is the approximate caloric storage in triglycerides within adipose cells?

2,500 - 2,800 kcal Signup and view all the answers

What is the recommended adequate intake of linoleic acid for adult males?

17 g Signup and view all the answers

What might excessive consumption of dietary fat lead to in terms of physical performance?

Impaired physical performance Signup and view all the answers

How does dietary fat primarily enter the body?

As triglycerides Signup and view all the answers

What do very low-density lipoproteins (VLDL) mainly contain?

Triglycerides Signup and view all the answers

What are the consequences of a diet low in saturated fats for cholesterol intake?

It allows intake to be between 100 and 300 mg/day Signup and view all the answers

Which type of fatty acid is alpha-linolenic acid classified as?

Omega-3 fatty acid Signup and view all the answers

What role do bile salts and lipases play in lipid metabolism?

They digest dietary lipids Signup and view all the answers

What happens to lipids once they are absorbed into the intestinal cells?

They form chylomicrons. Signup and view all the answers

What effect does exercise training have on fat metabolism during exercise?

It enhances fat utilization and aerobic performance. Signup and view all the answers

Which factor is mentioned as a potential ergogenic strategy related to fat metabolism?

Medium-chain triglycerides (MCTs) Signup and view all the answers

How do high-fat diets theoretically help delay the onset of fatigue?

By raising serum fatty acid levels Signup and view all the answers

What is a notable finding regarding acute high-fat diets and aerobic endurance performance?

They may impair performance due to gastrointestinal distress. Signup and view all the answers

What is the percentage of energy that chronic high-fat diets typically provide from fat?

50% or more Signup and view all the answers

What happens to muscle triglyceride levels with chronic high-fat diets?

They increase, potentially affecting fat use during exercise. Signup and view all the answers

Which of the following is NOT a proposed ergogenic supplement associated with fat metabolism?

Creatine Signup and view all the answers

What is a key advantage of increased fat oxidation due to training?

Sparing of muscle glycogen Signup and view all the answers

What effect does HCA have on endurance performance in humans?

Has no effect on endurance performance Signup and view all the answers

What is the main conclusion about CLA supplementation in resistance-trained athletes?

Has no effect on body composition Signup and view all the answers

What is the impact of high-fat diets on exercise performance according to the findings?

May impair exercise performance Signup and view all the answers

Which of the following is a characteristic of coronary heart disease?

Obstruction of blood flow in coronary arteries Signup and view all the answers

What is suggested about the adherence to a high-fat diet?

Difficult to adhere to Signup and view all the answers

Which of the following diseases is classified as a cardiovascular disease?

Arteriosclerosis Signup and view all the answers

What is identified as a primary risk factor for chronic diseases related to dietary fat?

Type of fat consumed Signup and view all the answers

What has some research indicated regarding ketone supplements and endurance performance?

Effects vary, sometimes improving, sometimes impairing Signup and view all the answers

What is a critical factor associated with the development of atherosclerosis?

High levels of LDL-cholesterol Signup and view all the answers

Which cholesterol ratio indicates average risk for atherosclerosis?

TC/HDL of 4.5 Signup and view all the answers

How can lifestyle changes potentially affect serum LDL-cholesterol levels?

Reduce LDL-cholesterol leading to a correlated reduction in heart disease risk Signup and view all the answers

Which condition is characterized by high total cholesterol?

Borderline high: 200 to 239 Signup and view all the answers

Which statement is true regarding HDL-cholesterol?

Higher levels are protective against heart disease Signup and view all the answers

According to the guidelines, what is a desirable level of LDL-cholesterol?

Less than 100 Signup and view all the answers

What is the impact of triglycerides on atherosclerosis risk?

High levels are associated with increased risk Signup and view all the answers

What role do statins play in cholesterol regulation?

They inhibit an enzyme that regulates cholesterol Signup and view all the answers

Study Notes

Essential Fatty Acids

Linoleic acid is an essential omega-6 fatty acid with AI of 17g for males and 12g for females.
Alpha-linolenic acid is an essential omega-3 fatty acid with AI of 1.6g for males and 1.1g for females.
Cholesterol intake should be between 100-300mg/day when following a low-saturated fat diet.

Excessive Fat & Cholesterol Consumptions

May be linked to heart disease and obesity.
Can displace carbs in diet, leading to excess calorie intake and body weight.
Can cause gastrointestinal distress.

Fat Metabolism

98% of dietary fat is triglycerides, and 2% is made up of sterols and phospholipids.
Bile salts & lipases digest fats into free fatty acids (FFAs), glycerol, cholesterol, and phospholipids.
Digested lipids are absorbed into intestinal cells and form chylomicrons, entering lymphatic system.

Lipoprotein Schematic

Chylomicrons are formed in the intestinal cells and contain a core of triglycerides with phospholipids and cholesterol arranged around the outside.
VLDL, LDL, and HDL lipoproteins transport lipids throughout the body.

Lipid Absorption

Chylomicrons enter circulation for breakdown, delivering fats to muscle and adipose (fat) cells.
Some fats, like MCTs, are taken directly to the liver.

Lipid Circulation

Chylomicrons circulate in the body to deliver lipids.
Body cells store lipids as triglycerides in adipose cells and muscle cells (IMTG).
Liver continually modifies lipoprotein composition.

Lipoprotein Types

Very low-density lipoproteins (VLDL) are primarily triglycerides and deliver fatty acids and glycerol to cells.
Most fat is stored in adipose cells for energy.

Fat as an Energy Source

Plasma chylomicrons & triglycerides are a minor source of energy for exercise.
Adipose cells have hormone-sensitive lipase which releases FFAs, raising serum FFA for muscle delivery.
Muscle cells have enzymes that release FFAs for use during exercise.
Epinephrine increases FFA release from adipose triglycerides to muscle.

Fat Use During Exercise

Mild exercise (25% VO2 max) uses ~80% of energy from fat, mostly from adipose tissue.
Up to 65% VO2 max, fat and carbohydrates contribute equally to energy expenditure.
Intensity ≥85% VO2 max relies on carbohydrates more heavily, dropping fat use to ≤25% as muscle glycogen becomes primary source.
Overall, FFA oxidation decreases as carbohydrate oxidation increases with higher exercise intensity.

Fat Use Limitations

Inadequate FFA mobilization can limit delivery to the muscle.
Impaired intramuscular metabolism can limit fat oxidation.
Increased carbohydrate oxidation can inhibit fatty acid oxidation.

Dietary Effects on Fat & Exercise

Lower carbohydrate intake decreases fat oxidation due to increased insulin inhibiting lipolysis and FFA oxidation.
Carbohydrate intake optimizes endurance performance.
As carb stores decrease and FFA use increases, exercise intensity must decrease.

Sex and Fat Use

Some studies show females oxidize more fat than males during submaximal exercise.
Other studies show no difference in carbohydrate or fat metabolism during exercise in equally trained individuals.

Exercise Training and Fat Metabolism

Exercise adapts the body to enhance fat utilization and aerobic performance.
Increased gene expression in skeletal muscles improves the capacity for fat oxidation.
With training, more energy from fat is used in exercise, sparing muscle glycogen.

Ergogenic Supplements

High-fat diets, fasting, lipid infusion, MCTs, lecithin, glycerol, omega-3s, hydroxycitrate, conjugated linoleic acid, phosphatidylserine, ketones, and caffeine have all been proposed as ergogenic supplements but research is mixed.

High-Fat Diets

Theory is that high-fat diets elevate serum FFAs and muscle triglyceride levels for increased fat use and glycogen sparing.
Acute high-fat diets (fat loading) do not enhance aerobic performance and may impair it if GI distress is caused.
Chronic high-fat diets don't enhance endurance performance and may not affect fat metabolism in sedentary or trained cyclists.

Conjugated Linoleic Acid (CLA)

CLA is marketed as a fat loss and muscle gain aid for athletes.
Limited research suggests no impact on body mass, fat mass, fat-free mass, or strength in resistance-trained athletes.

Ketone Supplements

Research is mixed, with some suggesting improved performance while others show impaired performance.
Poor gastrointestinal tolerance.

Ergogenic Fat-Burning Strategies Conclusion

Increased serum FFA availability and fat oxidation does not improve endurance exercise capacity.
High-fat diets may impair exercise performance.
Adherence to high-fat diets is challenging.

Dietary Fats & Cholesterol Health Implications

Dietary fat as a risk factor for chronic disease is associated with the type and amount of fat consumed.
A moderate fat diet reduces risk of chronic disease, emphasizing moderation.

Cardiovascular Disease Development

Many cardiovascular diseases exist, including coronary heart disease (leading cause of death), stroke, hypertension, rheumatic heart disease, and congenital heart disease.

Heart & Coronary Arteries

Coronary arteries supply the heart with blood.
Blockage of coronary arteries restricts blood flow and can cause heart attack.

Coronary Heart Disease

Arteriosclerosis is the thickening and loss of elasticity in arterial walls.
Atherosclerosis is the formation of plaque in arterial walls.

Atherosclerosis Development

Plaque buildup leads to narrowing of arteries and potentially blockage, causing thrombosis (blood clot formation).

Serum Lipids and Atherosclerosis

Total cholesterol, LDL-cholesterol, and triglycerides should be low.
HDL-cholesterol should be high.
Cholesterol ratios: TC/HDL (4.5 average risk) and LDL/HDL (3.5 average risk) should be low.

Risk Factors for Atherosclerosis

High Total Cholesterol
High LDL-cholesterol
High Dense LDL
High IDL-cholesterol
High Lipoprotein (a) (abnormal form)
High Apolipoprotein B
High Triglycerides
Low HDL-cholesterol
Low HDL-2-cholesterol
Low Apolipoprotein A-I

National Cholesterol Education Guidelines

Total Cholesterol: <200 desirable, 200-239 borderline high, ≥240 high
HDL Cholesterol: <40 low, ≥60 protective
LDL Cholesterol: <100 optimal, 100-129 near optimal, 130-159 borderline high, 160-189 high, ≥190 very high
Triglycerides: <150 normal, 151-199 borderline high, 200-499 high, ≥500 very high

Reversing Atherosclerosis

Each 1% reduction in LDL cholesterol can decrease risk of coronary heart disease by 1%.
Lifestyle changes, diet, exercise, and statin drugs are important in managing cholesterol levels.
Statins inhibit enzymes that regulate cholesterol.

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Description

This quiz explores the vital concepts surrounding essential fatty acids, their recommended intakes, and their role in fat metabolism. Additionally, it covers the health implications of excessive fat and cholesterol consumption, including risks associated with heart disease and obesity. Test your knowledge on these important nutritional topics!