ENERGY - CCEA - AS 2 NOTES

Needed for :

• internal functions
• external functions
• growth & repair
• maintenance

Water = facilitates chemical reactions that make energy from food

Calories vs Joules

Energy can be measured in : Kcal / C / J

Labels on food must have energy value given in both Kcal and KJ

1 Kcal = 4.184 KJ

ENERGY BALANCE = Intake = Expenditure ( ratio of input to output )

Intake = Energy in = Food & Drink

Expenditure = Energy out = Exercise

Eat more = Store excess kcal as fat  ( input > output )

Eat less = Use excess fat during exercise ( output < input )

Healthy weight = Balance output & input 

Appetite & Satiety center  ( nerve & chemical stimulation )

No exercise = Mechanism controlling input & output = less accurate = upset input & output = ENERGY IMBALANCE

+ ve      

Input > Output

• Excess fat accumulated ( Overweight )
• Large portion  + Ignore true appetite

______________________________________

-ve

Input < Output

• Fat stored used ( Weight loss )
• Fatty tissue depleted

Intake = Amount of energy absorbed through food intake

• BMR = Basal Metabolic Rate = Energy burnt when the body is at rest ( needed for proper functioning of organs )

What can affect the BMR:

• Body size = Big body needs more energy ( female = less lean tissue & more fat = lower BMR / male = more musscle - most metabolic tissue = ^ BMR - need more energy )
• Age ( Children = ^ BMR = small body / Adults = muscle deter - lower BMR )
• Thyroid = Secrete iodine into blood ( Thyroxin controls BMR - ^ BMR = overactive - underweight )
• Thermogenic effect = ^ BMR after food ( body create heat = help digest )
• Activity = oxygen uptake
• Growth = growing tissues and cells
• Mental energy = brain needs energy = support & protect brain cells ( stress drains energy )