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Energy balance & Energy expenditure explained.

Updated: Jan 7

ENERGY BALANCE IS THE INTERPLAY BETWEEN ENERGY TAKEN INTO THE BODY (IN THE FORM OF FOOD AND DRINK) AND THE ENERGY SENT OUT THROUGH OUR BODILY FUNCTIONS AND DAILY ACTIVITY.


THIS IS REFERRED TO AS THE FIRST LAW OF THERMODYNAMICS. THE LAW STATES THAT ENERGY CAN BE NEITHER CREATED OR DESTROYED, ONLY TRANSFERRED FROM ONE ENTITY TO ANOTHER.


WE CONSUME FOOD AND DRINK WHICH CONTAINS ENERGY, MEASURED IN CALORIES (KCAL). THESE CALORIES HAVE THREE MAIN PATHS OF USE IN THE BODY: WORK, HEAT AND STORAGE.


WHEN THE CALORIES COMING IN ARE EQUAL TO THE CALORIES BEING EXPENDED, BODYWEIGHT REMAINS THE SAME.


WHEN THE CALORIES COMING IN ARE GREATER THAN THE CALORIES BEING EXPENDED, BODYWEIGHT WILL INCREASE OVERTIME.


WHEN THE CALORIES COMING IN ARE FEWER THAN THE CALORIES BEING EXPENDED BODYWEIGHT WILL DECREASE OVERTIME.

FACTORS AFFECTING ENERGY BALANCE


ENERGY INPUT

  • CALORIE INTAKE: How many calories enter the digestive system from food and drinks.

  • ENERGY DIGESTED AND ABSORBED (90-99%) How many calories are extracted from foods as they pass through the digestive system. For those with well functioning GI systems this is 90-99%. Gastric issues can impair energy absorption, often resulting in weight loss.

ENERGY OUTPUT

  • EXERCISE ACTIVITY THERMOGENESIS (EAT) The energy expended during exercise.

  • NON-EXERCISE ACTIVITY THERMOGENESIS (NEAT) The energy expended during daily activity & movement.

  • BASAL METABOLIC RATE (BMR) The energy expended fuelling bodily functions whilst at rest

  • THERMIC EFFECT OF FOOD (TEF) The energy expended during digestion & absorption


TOTAL DAILY ENERGY EXPENDITURE (TDEE)


THE COMBINED TOTAL OF YOUR EAT, NEAT, TEF AND BMR IS REFERRED TO AS TOTAL DAILY ENERGY EXPENDITURE (TDEE) AND IS THE AMOUNT OF ENERGY YOUR BODY BURNS EACH DAY.


NON RESTING ENERGY EXPENDITURE (NREE)

EAT = 5%

TEF = 10%

NEAT = 15


RESTING ENERGY EXPENDITURE (REE)

BMR = 70%


INFLUENCING TDEE


BMR

  • BMR IS THE LARGEST COMPONENT OF TDEE.

  • IT CAN BE INFLUENCED TO SOME EXTENT BY INCREASING OR DECREASING BODY MASS.

  • A LARGER BODY REQUIRES MORE ENERGY TO RUN THAN A SMALLER BODY SO BMR WILL INCREASE WITH WEIGHT GAIN AND DECREASE WITH WEIGHT LOSS (1).

  • MUSCLE TISSUE IS SLIGHTLY MORE ENERGY DEMANDING THAN ADIPOSE TISSUE TO KEEP AROUND (ADIPOSE ~2KCAL/ LB VS. MUSCLE ~5-6KCAL/ LB)(2) AND IS ENERGY COSTLY TO CREATE INITIALLY (3).

  • THERE IS A GENETIC COMPONENT TO BMR.


NEAT


THE SECOND LARGEST PORTION OF TDEE IS NEAT. WE CAN INFLUENCE THIS BY BEING ACTIVE IN DAILY LIFE. THIS COULD BE BY TAKING MORE STEPS EACH DAY OR REGULARLY ENGAGING IN NON EXERCISE FORMS OF MOVEMENT.


Examples:

  • Parking further away from work/ school or getting off the public transport one stop early to walk.

  • Walking to speak coworkers rather than emailing.

  • At work, using the bathroom that's the furthest away.

  • Pacing whilst on the phone rather than sitting.

  • Walking up stairs rather than using escalators or lifts.

  • Adding in a regular morning, lunch time or evening walk, perhaps link up with a walking buddy for accountability.

  • Walk to and from work or school.

  • Orienting weekends around movement such as by visiting a new city, going for a hike, checking out a museum etc.

  • Taking up gardening or another labour intensive hobby.

TEF


  • IN A MIXED DIET TEF TYPICALLY CONSTITUTES TO 5- 15% OF TOTAL DAILY ENERGY EXPENDITURE.

  • PROTEIN HAS A HIGHER THERMIC EFFECT THAN CARBOHYDRATE OR FAT SO A HIGHER PROTEIN DIET LENDS WELL TO INCREASING TDEE (4)

  • IF WE WERE TO CONSUME 25G OF PROTEIN CONTAINING ~100KCAL WE WOULD EXPEND ~20- 30KCALS DIGESTING, ABSORBING AND DISPOSING OF THAT FOOD.

  • FOR A DAILY PROTEIN INTAKE OF 100G THIS LOOKS LIKE 80-120KCAL TEF ENERGY LOSSES EACH DAY.

IMAGE/ TREXLER, E., SMITH-RYAN, A. AND NORTON, L., 2014. METABOLIC ADAPTATION TO WEIGHT LOSS: IMPLICATIONS FOR THE ATHLETE. JOURNAL OF THE INTERNATIONAL SOCIETY OF SPORTS NUTRITION, 11(1), P.7.


1/ HALL, K., HEYMSFIELD, S., KEMNITZ, J., KLEIN, S., SCHOELLER, D. AND SPEAKMAN, J., 2012. ENERGY BALANCE AND ITS COMPONENTS: IMPLICATIONS FOR BODY WEIGHT REGULATION. THE AMERICAN JOURNAL OF CLINICAL NUTRITION, 95(4), PP.989-994.


2/ WANG, Z., YING, Z., BOSY-WESTPHAL, A., ZHANG, J., HELLER, M., LATER, W., HEYMSFIELD, S. AND MÜLLER, M. (2011). EVALUATION OF SPECIFIC METABOLIC RATES OF MAJOR ORGANS AND TISSUES: COMPARISON BETWEEN MEN AND WOMEN.


3/ SLATER, G., DIETER, B., MARSH, D., HELMS, E., SHAW, G. AND IRAKI, J., 2019. IS AN ENERGY SURPLUS REQUIRED TO MAXIMIZE SKELETAL MUSCLE HYPERTROPHY ASSOCIATED WITH RESISTANCE TRAINING. FRONTIERS IN NUTRITION, 6.


4/ WESTERTERP, K., 2004. NUTRITION & METABOLISM, 1(1), P.5.



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