ENERGY METABOLISM An overview for 7th and 8th grade students attending a Montessori Farm School Viola Holmes, MS, RD

What is Metabolism? The chemical changes in living cells by which the body grows, maintains itself, and breaks down tissue

2 Metabolic Processes: Anabolism – the building up of body tissues Catabolism – the breaking down of body tissues

Metabolism of Food Begins with eating (or ingestion) The food is broken down The products of digestion + O2 = energy Getting rid of waste materials

The 3 Dietary Sources of Fuel Cho = 9 calories/gram Pro = 4 calories/gram Fat = 4 calories/gram

Body fuel sources are: CHO --- Glucose PRO --- Amino Acids FAT --- Fatty acids Once digestion is completed we have these three

Carbohydrates to Glucose Provides our fastest and most efficient source of energy Absorbed from the digestive tract as glucose Glucose is maintained in the blood at constant levels so that it can be catabolized for energy when needed Produces CO2 and H2O waste products

Glucose Storage Glucose converts to glycogen for storage Glycogen is stored in the liver and muscles The body has limited glycogen stores When glycogen stores are filled excess glucose is converted to fat and deposited in adipocytes

Fats to Fatty Acids Fats are converted to fatty acids for fuel Alternate source of energy if cho stores are depleted Ketones are the waste product of fats and can be effectively eliminated by the urinary system (as long as they are not over produced)

Fat Storage Almost all cells can store fatty acids The body generates adipocytes for storage Adipocytes can be created but not destroyed Once fats are in these tissue, it is very difficult for the body to use them as an energy source

Proteins to Amino Acids Proteins are broken down to amino acids in the intestines and then go to the liver Broken down into 20 amino acids, which are required for cellular anabolism May undergo further chemical change to form hormones and digestive enzymes Alternate source of energy if cho stores are depleted Produces energy and nitrogen-containing waste product called urea

Amino Acid Storage Throughout the body amino acids are bunched up as proteins or they are freely available A.A.s have huge uses If excessive protein is consumed, there will be increased levels of protein in the urine

What is our preferred energy source? CARBOHYDRATES Breads, cereals, rice, pasta Fruits and fruit juices milk

The final step of food to fuel Once converted and stored, “foodstuffs” are available for use Glucose, fatty acids, and amino acids still need to be converted to ATP before they are used as energy ATP is the energy ATP = adenosine triphosphate

The Role of Vitamins Vitamins are accessory organic compounds They are essential to enhancement of the metabolism of cho, pro, and fats

An individuals energy needs depends on: Their basal metabolic rate (BMR) To maintain body temperature, to pump blood, for brain activity Their body composition Lean tissue requires more fuel than fat tissue Their activity level changes daily

Basal Energy Expenditure (BEE) Formula for males: 66+(13.7xwt kg)+(5.0xht cm)-(6.8xage) Formula for females: 655 + (9.6xwt kg)+(1.7xht cm)-(4.7xage)

Activity Factors Sedentary Adolescent – 1.3 Moderately Active – 1.4-1.5 Very Active – 1.5-1.7 Multiply BEE x Activity Factor = Daily Calorie Needs

A Balanced Diet Fuels Fitness 55-60% carbohydrates 15-20% protein 25-30% fat Fiber is also important