Daily energy expenditure consists of three components: basal
metabolic rate (BMR), diet-induced thermogenesis (DIT) and energy
cost of physical activity.
Thermic effect of food
Resting metabolic rate
Thermic Effect of Food
- Energy required to digest, absorb, transport, and store food.
- Diet induced thermogenesis (DIT) is different for each nutrient
based on the amount of ATP required for the initial steps of
metabolism and storage.
DIT (% Energy)
Acheson KJ, 1983
Westerterp KR, 1999
- In healthy subjects with a mixed diet, where intake equals
expenditure, DIT represents about 10% of the total amount of
energy ingested over 24 hours.
Westerterp, KR (2004) Diet induced thermogenesis, Nutrition
& Metabolism 2004, 1:5
- Daily Activity
- Aerobic exercise
- Expends calories during exercise
- Anaerobic exercise can increase metabolism for hours after
exercise is finished
- 3-14 hours: dependent upon intensity
- HIIT study: for every calorie
expended during anaerobics, 9 times as much fat (per calorie
expended) was metabolized as compared to aerobic activity.
- Online calculators
Resting Metabolic Rate
- Energy expended to maintain the body during resting conditions.
- Metabolic rate of muscle is about 10 to 15 kcal/kg per day,
or 4.5 to 7.0 kcal/lb per day.
- Contributes about 20% to Daily Energy Expenditure versus
5% for fat tissue (for individuals with about 20% body fat).
- Combined energy expenditure of the heart, lungs, kidneys,
brain and liver represent about 80% of the Daily Energy Expenditure.
- Have a metabolic rate that is 15-40 times greater than their
equivalent weight of muscle and 50-100 times greater than fat
- May account a smaller proportion of the daily caloric needs
for those who have regular vigorous exercise.
- Also see Calorie
Requirement Calculator and Toning
Elia M (1999). Organ and Tissue Contribution to Metabolic
Weight. Energy Metabolism: Tissue Determinants and Cellular Corollaries.
Kinney JM, Tucker HN, eds. Raven Press, Ltd. . New York: 61-79.
- Neutral energy balance is when the calories you take in is
equal to the calories expended.
- Positive energy balance is when the calories you take in
is greater than the calories expended.
- Weight is gained and fat stores are increased.
- One pound of fat contains approximately 3500 Calories.
- Negative energy balance: calories you take in is less than
the calories expended.
- Adipose, glycogen, and muscle can be used for energy to make
up the caloric deficiency.
- Ideally weight is lost and fat stores are reduced.
- Appetite is increased in proportion to energy expenditure
over a broad range of exercise intensities and durations to maintain
- However, formerly sedentary individuals show a net loss of
appetite when exercise is introduced.
Titchenal, CA. 1988. Exercise and food intake: What is
the relationship? Sports Medicine 6:135-45.
- The metabolism adjusts to changes in diet
- If calories are increased
- Metabolism increases
- Muscle mass may increase
- If calories are restricted
- Metabolism decreases
- Muscle mass may decrease
- A cascade of metabolic / hormonal changes allow the body