Energy Balance
a) Positive energy balance- when energy consumed is greater than energy expanded-results
in storage of energy mostly in form of TG. This is necessary
during pregnancy but also for infants and children-it leads
to weight gain.
b)Negative energy balance -Energy consumed is less than energy expanded-weight loss
occurs.
c) Energy balance -equilibrium-Energy intake equals energy output
Energy content of food is estimated by means of BOMB CALORIMETER
Use of nutrients
1) We use for energy mainly CHO We have limited ability to store CHO as Glycogen.
Beyond that we transfer CHO to fat and store it as TG
2) We have unlimited ability to store fat as TG in adipose tissue
3) We use protein for tissue synthesis, beyond this need it is used for energy , extra
protein is stored as fat .We have no ability to store amino acids.
Why are we hungry
Hunger-physiological need based on internal cues-Liver ,Gastrointestinal tract and brain
can give initiation for intake of food
Appetite-psychologically based intake of food. It is triggered by external cues-
birthday , time of the day-12 o’clock = lunch. Simply said it is a signal that
guides your dietary selections- you want something.
Satiety-refers to the state of fulness-no desire to eat any more food.
Internal forces regulating satiety
a) Distention of stomach and presence of food in small intestine.
B) Hypothalamus regulates satiety-hunger center
- satiety center
c) Nutrients in the blood-their presence after meal signals fullness-liver plays here
great roll .It signals brain through the Vagus nerve when
there are no more nutrients to be metabolized.
D) Neurological components-increased level of serotonin -neurotransmitter synthesized
from amino acid tryptophan decrease hunger and craving for
CHO.
-increased level of histamine- synthesized from from amino
acid histidine decreases food
intake and hunger.
e) Hormonal influences-Intestinal hormones-CCK, Secretin, Gastrin increases satiety
-increase in endorphin -natural pain killers,
insulin and cortisol leads to increased
feeding.-Insulin =high level contributes to
satiety, low level nincreases hunger.
-cortisol-increased level stimulates hunger
-leptin -secreted by adipose cells -high level
in blood=satiety
-low level
in blood = hungry
Psycho social factors influencing eating
- time of the day- lunch time , dinner time
-cold weather-increases appetite
-warm weather- decreases appetite
-Energy use
Body uses energy for 3 general purposes
1) Basal metabolism
2) Thermic effect of food
3) Physical activity
Basal metabolism -it is the minimum amount of energy needed to keep the resting awake
body alive. Includes heart beat, respiration Doesn’t include energy
need for physical activity and digestion
Women=0.9 kcal/kg/hour =21.6kcal/kg
Man =1kcal/kg/hour =24kcal/kg
BMR usually accounts for about 60-70% of daily energy expenditure in people of average
physical activity.
What influences BMR:
-body surface area ( the greater the greater BMR)
-gender ( males have higher)
-fever (increases BMR
-thyroid hormone-higher concentration increases BMR
-age (with advanced age BMR decreases-2% every decade after 30y)
-nutritional state (eating less slows BMR in short term. Eating 150-300kcal less
decreases BMR by 10-20%
-pregnancy-(increases BMR)
-caffeine and tobacco (increases BMR)
Thermic effect of food TEF
It is the extra energy used by the body during digestion, absorption, metabolism and
storage of energy yielding nutrients. It equals to 10% of total energy consumed. To
supply body with 100kcal person must thus eat 110kcal.
Physical activity
It contributes somewhere between 20-50% of total energy.
Estimating energy needs
Harris Benedict Equation
It is a way of estimating resting metabolic rate based on persons weight, height and age.
Estimating a desirable body weight.
Body mass index BMI
-It is the weight -for height standard used to define desirable body weight
-It is the most prevalent method to estimate healthy weight. Based on BMI we can
determine whether our current weight can be used as our desirable body weight
BMI-19-25 acceptable
26-28 low risk
30 and more way of determining obesity
40 and more very high risk
BMI is used for - adults
- Not for adults over 65
-Increased muscle mass doesn’t represent correct reading-athletes may
be overweight but not over fat. We are looking at fat ratio not muscle.
Formula to calculate BMI= Wt (lb) x 703.1
Ht (inch)
We define obesity either as-BMI over 30
-20% excess body fat
We define overweight as- excess of body fat by 10%
Body fat distribution
a) Android- apple shaped
-mostly in men
-due to high concentration of cortisol and testosterone as well as consumption of alcohol
-fat is mostly distributed around waist and belly- “pot belly”
-increases risk for -diabetes
-heart disease
-hypertension
-
b) Gynoid -pear shape
-mostly in women
-due to high concentration of estrogen and low concentration of cortisol
- fat is mostly deposited around buttock and thighs-they have skinny waist
1 lb of body fat =3500kcal. If you want to loose one pound of fat you need to create
deficit of 3500kcal. This can be done through deficit of 500kcal a day and will lead to
loss of a pound in a week.
