Lipids, fat and exercise

                                                Fats

n     a wide group of compounds that are generally soluble in organic solvents and largely insoluble
in water



n     solid (fats) or liquid (oils)



n     Subset of the class of lipids

      n    Simple lipids - fats (triglycerides) and wax

      n    Complex lipids – phospholipids, glycolipids, lipoproteins

      

n     Source of energy

    n   1 g fat = 9 kcal = 38 kJ

                                         Chemical structure

                                    Fatty acids –classification

n    The length of the carbon chain

    n   SCFA (< 6C) - butter

    n   MCFA (6 – 10 C) – butter, coconut and palm oil

    n   LCFA  (12 – 24C) – meat, fish, oil, seeds, nuts

n    The degree of unsaturation

  n    Saturated (SFA)

      n   fully loaded with hydrogen atoms, only single bonds

  n    Unsaturated

    n   Monounsaturated  (MUFA)  - 1 double bond

    n   Polyunsaturated (PUFA) - > 1 double bond

                                    Saturated FA – Stearic acid

                                         Monounsaturated FA

                                        Polyunsaturated FA 

                                    Fatty acids –classification

n     The location of double bonds (only PUFA)

  n    According the position of the double bond nearest the methyl end of the carbon chain

      n   Omega-3 fatty acids

      n   Omega-6 fatty acids

                                         Trans-fatty acids

                                            Cholesterol

n      Sterols

    n    Plant 

    n    Animal contain cholesterol (animal fat)

n      Roles of sterols

    n    Vitally important body compounds - bile acids, sex hormones (testosterone), sdrenal hormone
    (cortisol), vitamin D, cholesterol

n      Cholesterol – function

    n    Starting material for the synthesis of these compounds

    n    Structural compounds of cell membranes

n      Cholesterol – sources

  n     Endogenous – made in the body  0,8 – 1,5 mg per day

  n     Exogenous – form outside of the body (from food)  0,3 mg per day

  

n      Harmful effects of cholesterol

  n     It can form deposite in the artery walls (atherosclerosis => heart attacks, strokes)

                                       Roles of triglycerides

n     Fat store – store of energy (50 000 kcal)

n     Insulate of body, maintaining body temperature

n     Cover inner organs

n     Help body use carbohydrate and protein efficiently

n     Help absorption of fat soluble vitamins (A,D,E,K)

n     Source of essential fatty acids – linoleic and linolenic acid

n     Importance role in healthy skin and hair

n     Source of energy – FA and glycerol

                                     Digestion of triglycerides

n    Mouth and salivary glands

    n   lingual lipase

n    Stomach 

    n   lipid digestion by lingual lipase

n    Small intestine

    n   Fat by bile => emulsified fat

    n   Emulsified fat by pancreatic and intestinal lipase  =>  monoglycerides, glycerol, fatty
    acids





                                          Lipid transport

n     Lipoproteins

  n    Chylomicrons (CL)

    n   transport vehicles for fat from the intestine to the rest of body

  n    VLDL (very low density lipoproteins)

    n   Make from CL

    n   Transport TG to other part of the body

  n    LDL (low density lipoproteins)

    n   Transport cholesterol to the cells of all tissue

    n   Bad cholesterol – is linked to heart disease

  n    HDL (high density lipoproteins)

    n   Transport cholesterol  from the cells back to the liver

    n   Good cholesterol  - a protective effect

                                         Metabolism of fat

n    Storing fat as fat

  n    In adipose tissue

n    Making fat form carbohydrates or protein

  n    FA can be made form 2C fragments derived from carbohydrates or protein

n    Making fat from fat

n    Using fat for energy 60 % 

  n    During prolonged light  to moderate  intense exercise

                                      Health effects of lipid

n     Heart disease - ↑ chol  - major risk factor

n     Risks from saturated fat – ↑ LDL chol

n     Risks from trans-fats  =>  ↑ chol

n     Benefits from MUFA - ↓ risk for heart disease

n     Benefits from ω-3 PUFA - ↓ chol and prevent heart disease

n     Cancer – total fat intake (saturated) is associated with c.

n     Obesity – high-fat diets

                                     Recommended intakes of fat

n      Total fat < 30 % of energy intake

n      SFA < 10 % of energy intake

n      Cholesterol <  300 mg daily

n      Example

  n     A person 2000 kcal a day, 600 kcal and less form fat (65 g), 200 kcal and less form SFA (20
  g)

  

n      Select lean meats and nonfat milk

n      Eat plenty of vegetable, fruits and grains

n      Use fat and oils sparingly

n      Look for invisible fat

n      Read food labels

                                    Fat metabolism and exercise

n    Source of energy

      n   FA – oxidation in several types of tissue

      n   Glycerol – for glycolysis, gluconeogenesis

n    Fat mobilization

  n    Adipose tissue

  n    ↑ glucagon, epinephrine, cortisol 

      n   => hormone sensitive lipase (HSL)   - TG → FA

  n    ↑ FFA in the blood =>  ↑  oxidation FFA in the muscle (during exercise and
  fasting)

    

                                   Fat metabolism during exercise

n      Sources of FA  for muscle

  n     FA inside a muscle fiber

  n     FA outside a muscle fiber -  addipose tissue in muscle, in the body, circulatin lipoproteins

n      Hormonal influence

  n     Glucagon, kortisol =>  ↑  HSL (hormone sensitive lipase) => lipolysis

  n     Insulin =>  ↓ HSL => inhibition of  lipolysis

  n     Concentration of glucose in the blood

    n    ↑  =>  ↓ HSL

    n    ↓ => ↑  HSL

n      Time of oxidation 

  n     15 – 30 min. after start

                             Intensity of exercise and fat utilization

                                    Fat energy expended per hour
                                     and intensity of exercise