Nutrients and Energy in Food Macronutrients Micronutrients Energy

n Micronutrients Nutrients – are need to effectively extract energy from the macronutrients via catabolism macronutrients via catabolism n Macronutrients – Protein, Carbohydrate and Lipids –Contain stored energy n Vitamins and Minerals Vitamins and Minerals Vitamins and Minerals

Energy Content Energy Content n Carbohydrate contain 16 kj/gram Protein contain 17 kj/gram Protein contain 17 kj/gram Fat contains 37 kj/gram Fat contains 37 kj/gram n Alcohol contains 29 kj/gram

How is energy content of food measured? –Bombcalorimeter –Bomb calorimeter n Measures the energy released when the food is burnt food is burnt. n This includes energy from indigestible foods as well as digestible food. n The energy content of this "fibre" must be subtracted from the bomb calorimeter subtracted from the bomb calorimeter measurement. measurement.

Bomb Calorimeter Food Sample Thermometer Water Ignition fuse Bomb Water Tank Stirrer

The extraction of energy from food l Repackaging energy in ATP packets – Glucose = approx 100 ATP – But catabolism maximum yield is 38 ATP / glucose – as little as 0 ATP as in Brown Adipose Tissue The rest is lost as heat n Catabolism

Energy Needs of the Body n n Total Kilojoule Requirements Total Kilojoule Requirements The average day can be dived into three stages The average day can be dived into three stages : Rest, Energy need for each stage are about: Energy need for each stage are about: Rest, 2000kj Rest, 2000kj Work kj Work kj Play kj Play kj Over all per day = from 6000kj for total bed rest Over all per day = from 6000kj for total bed rest to 14,000 for a very active individual to 14,000 for a very active individual The need depend on body mass and sex The need depend on body mass and sex Work and Play

Basal Metabolism – The energy needs of the body at complete rest Is not really “basal” as it can change due to: Is not really “basal” as it can change due to: temperature and diet. o Used for all Internal energy needs oRecycle tissue oImmunity oBody warmth oReduced by Tissue decrease

Measure of energy needs of the body n Indirect Calorimetry measuring the amount of CO 2 breathed out measuring the amount of CO 2 breathed out. People can have a respirometer attached while moving n Whole body: people can be housed in a room people can be housed in a room connected to CO 2 monitors for air In and out

Which nutrients are used first for energy? n n Actually all macronutrients are used for energy all the time. Different material in different tissues eg.: The brain needs glucose Aerobic Muscles use fat The liver uses mainly excess protein The liver uses mainly excess protein.

Ideal Body Weight Obese

Calculate Body Mass Index (BMI) n n From % Body fat – –Measured with n n Skinfold thickness n n buoyancy n n Electrical conduction

Desire % Body Fat n n Body ConditionFemale Male n n Unhealthy <15% <10% n n Lean 17-22% n n Normal 22-25% 15-18% n n Above Average 25-29% 18-20% n n Over weight 29-35% 20-25% n n Obese 35+% 25+%

Dangers of Under and Over weight n n Framington study – – indicated obesity increased n n chance of early death n n cardiovascular disease n n diabetes

Framington Study From Kennel and Gordon 1974

Underweight n n Framington study indicated underweight increased – –chance of early death – –infectious disease – –cancer n n Anorexia nervosa and bulimia nervosa

Energy Use In Body

Weight Loss

Dieting

Fat distribution

Effect of fat distribution type n n Andomorphs – –More likely to suffer cardiovascular disease n n Gynomorphs – –Less likely to suffer cardiovascular disease

Benefits of Obesity n Obese people do not get osteoporosis n Obese people do not get osteoporosis. This may be due to their higher insulin secretion reducing calcium lost in the urine.

Causes of Obesity – –Nurture versus Nature

Nurture Theories Eating to satisfy : Eating to satisfy : Boredom Boredom Parents Parents Stress Stress Culture Culture Effect of age Effect of age Ego Ego s Most obese adults were slim when young Obesity may be caused by phycology

Nature Theories n n Obesity caused by physiology Dieting does not help Ageing Muscle tone Diet induced Thermogenesis Diet induced Thermogenesis Glycogen storage variations Glycogen storage variations Need large food intake to maintain Nitrogen Balance

Benefits of Obesity n Obese people do not get osteoporosis n Obese people do not get osteoporosis. This may be due to their higher insulin secretion reducing calcium lost in the urine.

Causes of Obesity – –Nurture versus Nature

Why Dieting Doesn't Work n Reduced energy intake causes the body to adapt: lowers “basal metabolism ” lowers “basal metabolism ” l burns up fat l reduces energy using tissue – lean body mass l When you go off the diet s use less energy s get fatter than before