This document discusses various topics related to food energy and metabolism. It defines food and food energy, and explains that food provides nutrients that animals use through cellular respiration to produce energy. It then discusses several units and concepts used to measure food energy and metabolism, including calories, respiratory quotient, specific dynamic action, net protein utilization, basal metabolic rate, and body mass index.

1. Food energy
Dr.P.Nithiya
Assistant Professor
DSCAS(W)
Perambalur

2. Food
• Food is any substance consumed to provide
nutritional support for the body.
• It is usually of plant or animal origin, and
contains essential nutrients, such as fats,
proteins, vitamins, or minerals.
• The substance is ingested by an organism and
assimilated by the organism's cells to provide
energy, maintain life, or stimulate growth.

3. Food Energy
• Food energy is energy that animals (including
humans) derive from their food, through the
process of cellular respiration, the process of
joining oxygen with the molecules of food
(aerobic respiration) or of reorganizing the
atoms within the molecules for anaerobic
respiration.

4. Units of energy
• Calorie
• Respiratory quotient
• SDA
•

5. Calorie
• The calorie equals the amount of thermal energy
necessary to raise the temperature of one gram
of water by 1 Celsius degree, at a pressure of 1
atm.
• For thermochemistry a calorie of 4.184 J is used,
but other calories have also been defined, such
as the International Steam Table calorie of
4.1868 J.
• Food energy is measured in large calories or
kilocalories, often simply written capitalized as
"Calories" (= 103 calories).

6. Respiratory quotient (RQ)
• The respiratory quotient (or RQ or respiratory
coefficient), is a dimensionless number used in
calculations of basal metabolic rate (BMR) when
estimated from carbon dioxide production.
• Such measurements, like measurements of
oxygen uptake, are forms of indirect calorimetry.
• It is measured using Ganong's Respirometer.
• It can be used in the alveolar gas equation.

7. Respiratory quotient (RQ)
• The respiratory quotient (RQ) is the ratio:
• RQ = CO2eliminated / O2consumed
• where the term "eliminated" refers to carbon
dioxide (CO2) removed ("eliminated") from the
body.
• In this calculation, the CO2 and O2 must be given
in the same units, and in quantities proportional
to the number of molecules. Acceptable inputs
would be either moles, or else volumes of gas at
standard temperature and pressure.

8. Specific Dynamic Action (SDA)
• Thermic effect of food (abbreviated as TEF),
also known as specific dynamic action (SDA) of
a food or dietary induced thermogenesis
(DIT), is the amount of energy expenditure
above the resting metabolic rate due to the
cost of processing food for use and storage.

9. SDA
• Simply, it's the energy used in digestion, absorption
and distribution of nutrients.
• It is one of the components of metabolism along with
resting metabolic rate and the exercise component.
• A commonly used estimate of the thermic effect of
food is about 10% of one's caloric intake, though the
effect varies substantially for different food
components.
• For example, dietary fat is very easy to process and
has very little thermic effect, while protein is hard to
process and has a much larger thermic effect.

10. Net protein utilization
• The net protein utilization, or NPU, is the ratio
of amino acid converted to proteins to the
ratio of amino acids supplied.
• This figure is somewhat affected by the
salvage of essential amino acids within the
body, but is profoundly affected by the level
of limiting amino acids within a foodstuff.

11. Net protein utilization
• Experimentally, this value can be determined by
determining dietary protein intake and then
measuring nitrogen excretion.
• One formula for NPU is:
NPU = ((0.16 × (24 hour protein intake in grams) - (24 hour urinary urea nitrogen) + 2) - (0.1 × (ideal body
weight in kilograms) / (0.16 × (24 hour protein intake in grams))
As a value, NPU can range from 1 to 0, with a
value of 1 indicating 100% utilization of dietary
nitrogen as protein and a value of 0 an indication
that none of the nitrogen supplied was converted
to protein

12. Basal metabolism Rate
• Basal metabolic rate (BMR) is the minimal rate
of energy expenditure by warm-blooded
animals at rest.
• It may be reported in units ranging from
watts/hour to ml O2/min or kJ per hour per kg
body mass.

13. Basal metabolism Rate
• Proper measurement requires a strict set of
criteria be met.
• These criteria include being in a physically and
psychologically undisturbed state, in a
thermally neutral environment, while in the
post-absorptive state (i.e., not actively
digesting food).

14. Body Mass Index
• The body mass index (BMI), or Quetelet index, is a measure
of relative size based on the mass and height of an
individual.
• The index was devised by Adolphe Quetelet during the
course of developing what he called "social physics",
between 1830 and 1850.
• The BMI for a person is defined as their body mass divided
by the square of their height—with the value universally
being given in units of kg/m2. So if the weight is in
kilograms and the height in metres, the result is immediate,
if pounds and inches are used, a conversion factor of 703
(kg/m2)/(lb/in2) must be applied.
• Body Mass Index = or