Fats and Exercise

Fats and Exercise Notes

Fats from Food

• Sources of dietary fats include:

  • Oils

  • Fried foods

  • Visible fat on meat

  • Nuts and seeds (some legumes)

  • Dairy products (milk, butter, cheese, yogurt)

  • Fatty fish

  • Butter, lard

  • Avocado

  • Coconut and palm oil

Functions of Body Lipids

• Body lipids perform multiple essential roles:

  • Cell membrane structure: Essential part of cell and nerve membranes, providing structural integrity.

  • Insulators: In adipose tissue, fats act as insulation and shock absorbers for organs.

  • Metabolism regulation: They assist in regulating metabolic processes.

  • Hormone synthesis: Cholesterol, a lipid, is a component of various hormones and is utilized by the liver to synthesize bile salts important for fat digestion.

  • Blood clotting: Phospholipids play a role in the clotting process.

  • Energy production: Free fatty acids (FFAs) are converted to acetyl CoA, which enters the Krebs cycle for energy production.

Lipids

• Definitions and forms of lipids:

  • Triglycerides (TG): Composed of glycerol and three fatty acids.

  • Phospholipids: Found in cell membranes.

  • Sterols: Include cholesterol, important for cellular functions.

Fatty Acids

• Classifications:

  • Saturated fatty acids (most animal-based foods):

  • Characteristics: Solid at room temperature.

  • Examples: Butter, cream, lard, meat.

  • Monounsaturated fatty acids (MUFA):

  • Characteristics: Liquid at room temperature.

  • Examples: Olive oil, canola oil, avocado.

  • Polyunsaturated fatty acids (PUFA):

  • Characteristics: Liquid at room temperature.

  • Examples: Safflower oil, sesame oil, soy oil, nuts, seeds.

  • Omega-3 and Omega-6 fatty acids: Important for various bodily functions.

  • Hydrogenated and partially hydrogenated fatty acids:

  • Trans fatty acids: Industrially altered fats that raise health concerns.

Omega-3 Fatty Acids

• Health benefits include:

  • Improved circulation

  • Enhanced vision and skin health

  • Reductions in inflammation

  • Support for neurological functions, including memory

  • May enhance blood flow, aiding endurance athletes.

  • Increased growth hormone secretion may promote muscle growth beneficial for strength/power athletes.

  • Useful for recovery from intense exercise bouts.

  • Potential benefits for head injury rehabilitation.

  • Improvement of lipid profiles and heart health.

  • Notable relationship between omega-3 and omega-6 fatty acids.

• Note on seed oils: "Relax!"

Glycerol

• Description:

  • Glycerol is a type of alcohol.

  • Dietary sources come from triglycerides.

  • Metabolized in the body as a by-product of carbohydrate metabolism.

  • Capable of being converted back to carbohydrates via gluconeogenesis in the liver.

Cholesterol

• Description:

  • Cholesterol is a sterol and is classified as non-essential (can be synthesized by the body).

  • Produced in the liver of animals.

  • Food sources include only animal products, with plant sterols being the exception.

Phospholipids

• Functions:

  • Emulsify fats and provide structure to cell membranes.

  • Considered non-essential, meaning they can be synthesized by the body.

  • Food sources include:

  • Egg yolks

  • Liver

  • Wheat germ

  • Peanuts

Fat Digestion & Absorption

• Complexity due to the insolubility of lipids in water.

• Occurs in the small intestine with assistance from:

  • Bile, released from the gallbladder.

  • Lipase enzymes from the pancreas.

Digestion & Absorption Process

• Digested fats are absorbed into intestinal mucosa cells and combined into chylomicrons (lipoproteins).

• Chylomicrons then:

  • Exit the intestinal cells

  • Transported to the lymphatic system (lacteal) before entering blood circulation.

• Lipids cannot float freely in blood and require lipoprotein "escorts" for transportation.

Fate of Fats in Muscle and Adipose Tissue

• Lipids serve multiple functions:

  • Energy source: Used directly for energy.

  • Storage: Stored as triglycerides in muscles or adipose tissue for later use.

  • Transport to liver: Glycerol and leftover chylomicron remnants are transported to the liver to assist in lipoprotein formation.

Types of Lipoproteins

• Very Low-Density Lipoproteins (VLDL):

  • Composed primarily of triglycerides.

  • Responsible for transporting triglycerides to tissues to provide fatty acids (FA) and glycerol.

• Low-Density Lipoproteins (LDL):

  • Contains cholesterol and phospholipids with minimal triglycerides.

  • The main function is to transport cholesterol to cells.

• High-Density Lipoproteins (HDL):

  • Higher in protein content (45-50%) with moderate cholesterol and phospholipid content, and minimal triglycerides.

  • Responsible for "reverse cholesterol transport", moving cholesterol away from cells.

Ketones

• Description:

  • Ketones, or ketoacids, are by-products of excessive fatty acid metabolism.

  • Can be produced during:

  • Fasting

  • High-fat diets

  • Diabetes

  • Serve as an alternative energy source.

  • Accumulation in the blood leads to acidosis, which is unhealthy and not recommended for athletes.

Ketogenic Diets: Performance Facts

• Studies on low-carbohydrate-high-fat (LCHF) or ketogenic diets report:

  • No significant difference in endurance capacity at low/moderate intensities (62-64% VO2max) when comparing ketogenic diets to mixed diets.

  • Smaller training adaptations were noted after 7 weeks on high-fat diets compared to high-carbohydrate diets.

  • Some reductions in peak power output and endurance performance in athletes consuming high-fat diets.

Fats and Exercise

• ATP Production: Two major sources during exercise are carbohydrates (CHO) and fats, with a mixture of both fuels utilized.

• Hormonal Response: During exercise, epinephrine is secreted, which stimulates:

  • Breakdown of triglycerides in adipose cells.

  • Release of free fatty acids into the bloodstream.

Fuel for Exercise

• Energy contribution changes with exercise intensity:

  • At 25% VO2 max:

  • 20% or less from carbohydrates, 80% from fat.

  • At 65% VO2 max:

  • Carbohydrates and fats contribute equally.

  • At > 85% VO2 max:

  • Energy contribution from fats drops below 25%, with muscle glycogen becoming the preferred energy source.

Effects of Exercise Training on Fat Metabolism

• Trained athletes exhibit:

  • Greater fat utilization compared to untrained individuals during standardized exercises.

  • Enhanced blood flow and capillarization in muscle, enabling better delivery of plasma-free fatty acids.

  • Increased sensitivity of muscle and adipose cells to epinephrine.

  • Enhanced ability to use ketones as energy sources.

  • Elevated activity of metabolizing enzymes for fat.

Interventions for High Cholesterol

• Strategies to manage cholesterol levels include:

  • Maintaining an appropriate amount of dietary fats.

  • Noting that dietary saturated fat raises blood cholesterol more than dietary cholesterol does.

  • Recommendations to reduce saturated fat intake to < 7-10% of total caloric intake (calculated in grams).

  • Encouraging increased consumption of monounsaturated and polyunsaturated fats.

  • Raising intake of omega-3 fatty acids.

  • Including more soluble fiber in the diet.

  • Addressing elevated triglycerides by assessing sugar and fiber intake.

  • Considering conservative treatment approaches in young athletes, especially those with genetic predispositions to high cholesterol levels.