Calories In vs. Calories Out
DEFINITION
Calories in vs. calories out refers to the basic principle that weight loss occurs when you burn more calories than you consume, while weight gain occurs when you consume more calories than you burn.
EXPLANATION
- Your body requires a certain number of calories each day just to perform basic bodily functions like breathing, cell repair, digestion, etc. This is known as your basal metabolic rate (BMR).
- Any additional physical activity will burn extra calories above your BMR.
- If you consume the exact number of calories needed to maintain your current weight, you will remain the same weight.
- To lose weight, you need to create a calorie deficit by consuming fewer calories than you burn on a daily basis. The larger the deficit, the faster the weight loss.
- To gain weight, you need to consume more calories than you burn consistently. The excess calories will be stored as fat or muscle.
EXAMPLES
- A sedentary 150 lb person has a BMR of about 1600 calories per day. If they consume 1600 calories, they will maintain 150 lbs.
- If that same person starts exercising and burns 300 calories through exercise, their daily calorie needs increase to 1900 calories (BMR + exercise calories).
- To lose 1 lb per week, they need a daily deficit of 500 calories, so they should aim to consume just 1400 calories per day (1900 – 500 = 1400).
RELATED TERMS
- Basal metabolic rate (BMR)
- Calorie deficit
- Calorie surplus
- Macro nutrients (protein, carbs, fat)
COMMON QUESTIONS
- How many calories should I eat to lose/gain weight? Calculate your BMR and adjust based on your activity level and weight goals.
- What about metabolism differences between people? Metabolic differences only account for a couple hundred calories. The principle still applies.
- Isn’t weight loss more complicated than calories in vs out? Hormones, genetics, etc. do play a role but calorie deficit is still required for weight loss.
DO NOT CONFUSE WITH
- Starvation mode – severe calorie restriction can cause adaptive metabolic slowdown. Mild calorie deficits for weight loss do not.
- Body recomposition – losing fat while gaining muscle. Calorie balance affects scale weight, not body composition.
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