Understanding Energy Balance and Its Impact on Weight
Energy Balance
Energy balance: E = E consumed – E expended
This equation states that body weight is kept constant when caloric intake (potential chemical energy of food eaten daily) equals energy expenditure (energy expended during the course of the day).
Types of Energy Balance
- Energy Balance: Occurs when the approximate calories consumed equal the calories expended during the course of the day, thus maintaining a stable weight.
- Positive Energy Balance: In this case, you eat more calories than are expended, and consequently, gain weight because the excess calories are stored as fat in the body’s fat deposits. It has been estimated that for every 3,500 calories consumed in excess, one pound of fat (0.45 kg) is stored in the body. In summary, weight increases (by accumulation of excess calories) if there is an increase in caloric intake or a decrease in human movement (exercise or physical activity).
- Negative Energy Balance: If, on the contrary, the total calorie intake is smaller in relation to expenditure, the individual loses weight. If the energy deficit is 3,500 calories, one pound of fat is lost. Weight loss may be caused by increased exercise or decreased calorie consumption.
Components of Energy Expenditure
Energy Consumption at Rest
The minimum amount of energy consumed that is compatible with life. The amount of energy used in 24 hours when a person is lying down, in physical and mental rest for at least 12 hours after the last meal, in a thermoneutral environment. Energy is spent on activities necessary to maintain normal body functions and homeostasis.
Basal metabolism, basal energy consumption (BMR)
- Includes breathing, circulation, synthesis of compounds
- Body temperature maintenance
Factors Affecting Energy Consumption at Rest
- Age
- Gender
- Body Composition
- Hormones
- Fever
- Fasting
- Surface Area
- Other factors
BMR is higher in:
- Young people
- Larger surface area
- Stress, Hyperthyroidism, fever
BMR is lower in:
- Fasting
- As we age
- Hypothyroidism
- Malnutrition
Diet-Induced Thermogenesis (DIT)
Mandatory Component: It is the energy required to digest, absorb, and metabolize nutrients. 6-10% of total kcal
Optional Component: The energy that is consumed in excess can be eliminated by activating metabolic inefficiency through a system of uncoupling proteins of oxidative phosphorylation.
Factors affecting DIT:
- Type of macronutrient: it is greater after carbohydrate intake than fat and protein.
- Regularity of meals
- Some nutrients stimulate DIT (carotenoids, retinoic acid, amino acids)
- Other: spicy foods, caffeine, etc.
Energy Expenditure for Physical Activity
The cost of energy by voluntary movement is the body’s overall energy component that presents greater variability between individuals, and until recently, the most difficult to determine. It depends on:
- Number of muscles involved
- Weight
- Time
Measurement Units:
- Kcal / weight / time
- VO2 / weight / time
Calorimetry Measures Energy Expenditure
Direct Calorimetry
Requires calculating all the heat that enters or exits the chamber. Easily understood but difficult to perform.
- Heat of vaporization of water from lungs and skin
- Heat/freshness of food and drink
- Hot urine and feces
- Other sources of heat in the chamber: lights, televisions
The individual is situated in an airtight chamber, and the heat produced is determined.
Indirect Calorimetry
It is based on the fact that the combustion of nutrients consumes oxygen in an amount proportional to the energy released as heat.