chapter
chapter
85
Fluid
and
Energy
and
Electrolyte
Balance
Nutrient Balance
Prof Jennifer Broxterman, RD, MSc
FN3373: Nutrition for Physical Activity
Lecture 7
Author name here for Edited books
Introduction
• Most individuals maintain a stable weight
over time
– How is it possible to maintain a stable body weight
within such a narrow range, especially when we pay
little attention to the amount of energy we eat or
expend each day?
Energy & Macronutrient
Balance Equations
Energy Balance
• Energy balance equation:
– Energy intake (total kcals consumed) equals energy
expenditure (total kcals expended)
– Intakes of protein, CHO, fat, and EtOH must also
equal their oxidation rates to achieve energy balance
• Factors affecting energy balance:
–
–
–
–
–
Genetic makeup
Dietary intake and habits
Physical activity and activities of daily living
Environmental conditions
Lifestyle
Energy and Nutrient Balance Equations
Required for Long-Term Weight
Maintenance
Chocolate Chip Cookie Mystery
• What would happen if you consumed an
extra chocolate chip cookie (~100 kcal)
every day for 40 years?
Macronutrient Balance
Macronutrient Balance
• Energy intake / energy expenditure is only one
component of the energy balance equation
• Changes in the type & amount of macronutrients
consumed (CHO, protein, fat, EtOH) and the
oxidation of these nutrients within the body must
be considered
• Under normal conditions:
– CHO, protein, and EtOH are not easily converted into
body fat
Carbohydrate Balance
• CHO balance is tightly regulated by the body
– Ingestion of CHO stimulates both glycogen storage and
glucose oxidation and inhibits fat oxidation
– Glucose not stored as glycogen is oxidized directly in
almost equal balance to that consumed
– What happens when large amounts of CHO are
consumed?
Figure 5.1
Carbohydrate Intake &
Glycogen Storage
• Glycogen storage:
– The body’s storage sites for glycogen are limited to
the liver and skeletal muscle
– Glycogen storage fluctuates greatly in response to:
• Feeding – increases glycogen stores
• Exercise – depletes glycogen stores
– Becoming physically fit increases one’s ability to
store glycogen, making this carbohydrate
unavailable for conversion to body fat
Protein Balance
• Protein (nitrogen) balance:
– The body adjusts to a wide range of protein intakes
by altering the oxidation rate of dietary protein
– After anabolic needs are met, carbon skeletons of
any excess aa’s are diverted into the energy
substrate pool
– Inadequate intakes of either energy or CHO result in
negative protein balance and may adversely affect
the balance of individual aa’s
– Excess protein consumed may contribute indirectly
to fat storage by sparing dietary fat
Fat Balance
• Fat oxidation:
– As fat intake increases, fat oxidation does not
increase proportionally
– Body adipose stores are large
• Excess energy eaten as dietary fat is stored as triglycerides
in adipose tissue
• Little energy is consumed in the storage process
– What happens in long-term positive fat balance?
Figure 5.3a
Figure 5.3b
Figure 5.3c
Figure 5.3d
Figure 5.3e
Figure 5.3f
Alcohol Balance
• Alcohol (EtOH) oxidation:
– EtOH is a “priority fuel”
– Suppresses the oxidation of fat and to a lesser extent
that of protein and CHO
– EtOH is not converted to TG and stored as fat
– 7 kcal/g
Energy Expenditure
Components of Energy Expenditure
1. Resting Metabolic Rate (RMR)
Basal Metabolic Rate (BMR)
Resting Energy Expenditure (REE)
2. Thermic Effect of Food (TEF)
3. Energy Expended in Physical Activity and
Activities of Daily Living
(Thermic Effect of Activity – TEA)
Figure 5.5
Biological Factors that Influence RMR
• Age:
– RMR declines ~1-2% per
decade from the 2nd through
the 7th decade of life
• Gender:
– Men generally have larger RMRs
than women because on average
they usually weigh more and have
more fat-free mass
Biological Factors that Influence RMR
• Genetics:
– RMR has a genetic component
– Parent-child and twin studies
• Body temperature:
– RMR increases as body temp.
increases above normal (fever)
– What about the relationship
between RMR and body temp.
within normal temp. ranges?
Biological Factors that Influence RMR
• Reproductive hormones:
– Menstrual cycle
fluctuations in RMR
– Difference of 100-300
kcal/day
Physical Activity Factors
that Influence RMR
• Exercise can affect energy expenditure both
directly and indirectly:
– Metabolism increases during exercise, increasing
the amount of energy expended
– Exercise can also increase the
amount of FFM, elevating RMR
Physical Activity Factors
that Influence RMR
• Research questions:
– Does aerobic training increase RMR?
– For a given individual, does becoming more
physically fit increase RMR?
– Does metabolic rate stay elevated after exercise is
over?
Figure 5.12
Table 5.2
Factors that Influence the
Thermic Effect of Food
• Effect of food composition (macronutrients):
– Thermic effect of fat = 3-5%
– Thermic effect of glucose = 5-10%
– Thermic effect of protein = 20-30%
• Energy cost of storing macronutrients:
– Converting dietary CHO & protein to stored fat
requires more energy than converting dietary fat to
stored fat
• Meal size:
– A meal higher in calories will have a higher TEF
compared to a low-calorie meal
Predicting Energy
Expenditure
Equations for Estimating Resting
Metabolic Rate (RMR) in Healthy
Individuals
World Health Organization’s Equations for
Estimating RMR in Healthy Individuals
Equations for Estimating Resting
Metabolic Rate (RMR) in Healthy
Individuals
Figure 5.15