Energy

Principles of nutrition - NIN 1232Prof. Chandrani Liyanage

Objectives Sources, and needs of energyEnergy expenditure and measurementEnergy balance and regulationEnergy requirements

Body needs energy For - Repair of body tissues continously

- Growth

- Work

Food sources of energyCarbohydratesFatsProteins (in starvation)Alcohol (but not recommended as harmful)

Atwater factors Single energy value for each of the source

Carbohydrates 4.0 kcl/gFats 9.0 kcl/gProtein 4.0 kcl/gAlcohol 7.0 kcl/g

Energy expenditure The total energy expenditure from the body is on

1. Basal metabolism 2. Physical activity3. Thermogenic effect of foods

1. Basel Metabolic Rate (BMR) Amount of energy required by a normal healthy person at complete rest and at post absorptive state (12 hours of fasting) for - activity of the internal organs (muscle contraction, heart beat, cell growth and multiplication) Single largest contributor (accounting to 60-70%) to TEE (total energy expenditure) During sleep the overall metabolic rate approximates to BMR.

BMR depends onAgeGenderBody weight

For a 65kg man BMR is 7.56 MJ/dayFor a 55kg woman BMR is 5.98 MJ/day

Factors affecting BMRAge - increased BMR in young age due to more lean massSex - increased BMR in malesBody composition increased BMR due to more lean massPhysical activity - increased BMRGrowth - pregnancy, childhood increased BMRStress - increased BMR

Starvation decreased BMR

2. Physical activityOnly 25-35% of nutrient energy is used for mechanical work

3. Thermogenic component The energy expenditure through the physiological response following ingestion of food, and exposure to cold or stimulants

About

Energy balance Energy balance Energy consumed = energy expended + change in body weight Energy consumed = TEE ( BMR, PA, TEF)

Positive energy balance Energy intake energy expenditure = +ve valueSeen in : Weight gain Growing children Pregnant women Obesity & over weight

Regulation of body weight Depends on - balance between nutrient intake and utilization - amino acid oxidation is adjusted to AA intake - CHO oxidation is adjusted to CHO intake Glycogen reserves are maintained at a balanced amount (excess CHOs are channeled into lipid stores) - Fat balance is not regulated, therefore, excess goes to stores (fat oxidation and metabolism are not dependant on fat content of the meal). Fatty meals lead to fat accumulation and obesity.

Negative energy balance Occurs when:

Energy intake less than energy expenditureWeight lossStarvationPatientsExcess physical activity in sports activities

Basel Energy Expenditure (BEE)Consists of 3 components:

Resting metabolism E cost of normal metabolic processes of the bodyAdaptive involuntary E expenditure - to cope with cold conditionsEnergy associated with absorbing and metabolizing food

Measurement of BEEUsing Harris Benedict equation

For men: BEE = 66.473 + (13.7516 x wt in kg) + (5.0033 x ht in cm) (6.775 x age in y)

For women:BEE = 655.0955 + (9.5634 x wt in kg) + (1.8496 x ht in cm) (4.6756 x age in y)

E expenditureLight work: (2.5 kcl/minute) PAL for men 1.55 and for women 1.56Moderate work: (5-7.4 kcl/minute) PAL for men 1.78 and for women 1.64Heavy work: (10-12.5 kcl/minute) PAL for men 2.10 and for women 1.82

Energy for activityDaily E expenditure = BMR x (time in bed) + (time at work x PAR) + (non- occupational time x PAR)PAR (physical activity ratio) - is an estimate based on the duration and type of physical activity PAR = E cost of an activity per minute E cost of BMR per minute For relaxation - 1.4 x BMRFor gentle walking - 4 x BMRFor sleeping - 1 x BMR For light & domestic work - 2 x BMRFor heavy household work - 4 x BMRFor very heavy breathless activities - 7 x BMR

Measurement of E outputHeart-rate monitoring - simple method for measuring TEEDirect calorimetry - measures heat produced and excretion of water & CO2Indirect calorimetry - Heat production is determined from the O2 and CO2 productionDoubly labeled water method most accurate method,

E requirementsTotal calorie requirements = BEE x sum of the stress and activity factorsTEE = BMR x PALPAL (physical activity level) Ratio of overall energy expenditure to BMR PAL of 1.9 reflects very active work pattern PAL of 1.4 minimum activity at work

E requirements In young children: For boys at 3 years 1.7MJ (450 kcl/kg/day) 9 y - 1.2 MJ (290 kcl/kg/day) For girls at 3 years - 1.6 MJ (385 kcl/kg/day) 9 y - 1.1 MJ (255 kcl/kg/day)In adolescents and adults with PAL of 1.4: For males - 10.6 MJ (2550 kcl/day) For females - 8 MJ (1900 kcl/day) PAL is characterized by a description of life style

In pregnancy: Energy cost for changes in tissue mass 167 MJ (40,000 kcl) Total increase in BMR - 126 MJ (30,000 kcl) Overall total energy requirement - 293 MJ (70,000 kcl)

Estimated adequate requirement (EAR) - 0.8 MJ/day (200 kcl/day) above the pre pregnant EAR

Women who are either underweight, or do not reduce their activity, or teenage mothers need extra calories.In lactation: Additional E requirement 1.9 - 2.4 MJ (450-570 kcl/day)