If your goal is weight loss, you must burn more calories than you consume. This principle is known as energy balance, which compares the energy you take in from food and drink against the energy your body expends daily. Weight loss requires the body to use more energy than it receives, forcing it to access stored energy reserves, primarily body fat, to make up the difference. This process provides the scientific basis for all successful weight management strategies.
The Fundamental Principle of Energy Balance
The simple equation of “Calories In versus Calories Out” (CICO) dictates the direction of your body weight over time. Calories consumed represent the “energy in,” while your Total Daily Energy Expenditure (TDEE) represents the “energy out”—the sum of all calories burned to stay alive and move.
There are three states of energy balance. Caloric maintenance occurs when calories consumed equal calories expended, keeping weight stable. A caloric surplus (consuming more energy than you burn) leads to weight gain as excess energy is stored.
For weight loss, a caloric deficit is mandatory, meaning energy expenditure must exceed energy intake. Achieving this deficit is the non-negotiable requirement for reducing body mass. The body must be forced to mobilize stored energy, and a deficit is the only signal that triggers this mobilization. While food quality is important for health, the net energy difference is the factor that drives weight loss.
Components of Daily Caloric Expenditure
The “burn more” side of the equation, your Total Daily Energy Expenditure (TDEE), is complex. TDEE is composed of several distinct factors, with the largest portion dedicated to simply sustaining life.
Basal Metabolic Rate (BMR)
BMR represents the energy required for the most basic, life-sustaining functions, such as breathing, circulation, and cell production, while the body is at complete rest. BMR typically accounts for 60 to 75 percent of the average person’s total daily calorie burn, making it the largest component of expenditure.
Thermic Effect of Food (TEF)
TEF is the energy your body uses to digest, absorb, and process the nutrients from what you eat. This process generally accounts for about 10 percent of your total calories burned each day.
Physical Activity
The remaining portion of TDEE is related to physical activity, which is divided into two categories. Non-Exercise Activity Thermogenesis (NEAT) includes all the calories burned from movement that is not formal exercise, such as fidgeting, standing, walking, and maintaining posture. The final component is the calories burned during planned Exercise Activity Thermogenesis (EAT), which is the energy expended during structured workouts.
The energy burned through NEAT and EAT combined is the most variable part of TDEE. While exercise is often the focus, small, consistent increases in NEAT throughout the day can also contribute significantly to the overall energy expenditure.
Strategies for Achieving a Safe Caloric Deficit
Creating the necessary caloric deficit can be accomplished by reducing energy consumed, increasing energy expended, or combining both strategies. A sustainable goal is a daily deficit of approximately 500 calories. This reduction is estimated to result in the loss of about one pound of body fat per week, which is considered a safe and healthy rate of progress.
To achieve this 500-calorie deficit, you might cut 250 calories from intake and burn an extra 250 calories through increased physical activity. This balanced approach is often easier to maintain than making extreme changes to diet or exercise alone.
Reducing intake involves monitoring portion sizes and making nutrient-dense food choices that promote satiety. Increasing expenditure means engaging in regular, structured exercise and consciously raising your NEAT by moving more throughout the day. Consistency is the most important factor, as the deficit must be maintained daily for the body to tap into its energy stores. Monitoring progress and making small adjustments ensures the deficit remains appropriate for long-term success.