Jay Snaric

What Affects Metabolism and Energy Expenditure

There are 3 Components of Energy Expenditure. They are Basal Metabolism, Physical Activity, and the Thermic effect of food. If you spend more energy on these components then you take in (i.e. eat food), then you will lose weight. 

Components of Energy Expenditure

            1. Basal Metabolism

            2. Physical Activity

            3. Thermic effect of food 

1. Basal Metabolism

            -2/3 of energy expenditure

            -energy used to support basic processes of life

                        -breathing, heart pumping, brain functions, kidneys, etc.

            -Basal Metabolic Rate (BMR) - rate at which person spends energy at rest

            -Factors affecting BMR

                        -lowest during sleep  

                        -lean muscle mass - weight of body minus fat

                                    -­ lean muscle, ­ BMR

                                    -males have higher BMR than females

                        -¯ w/ age, because of ¯ lean muscle mass

                        -­ w/ height, because of ­ surface area to radiate off heat (energy)

                        -Growth --- ­ growing child, ­ pregnancy

                        -­ fever - production of heat (energy)

                                    -speeds metabolism of immune system, fight infections

                        - ­ caffeine and nicotine

                        - ­ stress and disease

                        - ¯ fasting and starvation      

2. Physical Activity

            -Voluntary movement - skeletal muscle

            -most variable component of energy expenditure

                        -­ influence on weight loss/gain

            -Amount of energy needed for activity depends on:

                        -muscle mass - ­ muscle used, ­ energy used

                        -body weight - ­ body weight, ­ energy used

                                    -need more energy to move larger body

                        -activity

                                    - ­ (duration, frequency, and intensity), ­ energy used

                        -an obese person may spend more overall energy doing a task, but

generally will have a lower BMR than a person who weighs less and has a greater lean body mass            

3. Thermic effect of food

            -energy required to process food - digestion, absorption, movement, etc.

            -10% of energy intake

Estimating Energy Requirements

Basal metabolic rate – estimating with age, gender, weight, and height

            What this does not take into account is body composition.

1. Convert weight from pounds to kilograms

            * 2.2 lbs = 1 kg

* weight in lbs / 2.2 lbs/kg = ______kg

2. Convert height in inches to cm

            * 1 inch = 2.54cm

            * height in inches x 2.54 cm = _________ cm

3. Plug into Harris-Benedict equation

Male

            BMR = 66 + (13.7 x wt. in kg) + (5 x ht in cm) – (6.8 x age in yrs)

Female

            BMR = 655 + (9.6 x wt. in kg) + (1.8 x ht in cm) – (4.7 x age in yrs)

To estimate energy values for physical activity.

            *Multiply activity factor by BMR

-Very light – multiply by 1.3.

                        -driving, typing, sewing, cooking

-Light – multiply by men (1.6) and females(1.5)

            -housecleaning, golf, carpentry

            -Heavy – multiply by men (2.1) and females (1.9)

                        -heavy exercise, running, weightlifting

Body Mass Index (BMI) – weight to height relationship

            -BMI = weight (lb) / height (inches)2 x 705

BMI < 18.5 = underweight

BMI 18.5 to 24.9 = normal

BMI 25 to 29.9 = overweight

BMI > 30 = obese

Article Tags: Physical Activity            

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