Understanding the Weight Loss Equation

1. You input energy when you eat.
2. The food you consume provides calories.
3. Calories are simply a unit of energy or heat.
4. The food you eat and the drinks you consume provide different amounts of energy. 

For example:
Protein and carbohydrates each provide 4 calories per gram, while fat provides 9 calories per gram.

Energy output happens when your body uses energy. It is often referred to as “burning” calories. 

Even when you’re sleeping, your body uses energy to perform basic functions like breathing and circulating blood. 

The rate at which your body burns calories at rest is called your basal metabolic rate (BMR). BMR makes up roughly 60% to 75% of the total number of calories you burn each day.

You also expend energy during activities of daily living, like washing dishes or shopping, and of course, through physical exercise.

Positive Energy Balance
 

A positive energy balance occurs when your energy input is greater than your energy output. 

That is, you eat more calories than your body uses. Your body stores excess energy or calories as fat. This results in weight gain.

Energy Input > Energy Output = Weight Gain

Example:
Calories consumed each day: 2,000
Calories burned each day: 1,750

2,000 (energy input) – 1,750 (energy output) = 250 calories

There is a positive energy balance of 250 calories per day. 

That doesn’t sound like much. But over the course of a week, the estimated balance would be 1,750 calories or about enough to gain a half pound of weight.

Negative Energy Balance

Weight loss occurs when you create a negative energy balance. 

That is, you burn more calories than you consume. When this imbalance occurs, your body burns stored energy (fat) in order to function and you lose weight. 

A negative energy balance is sometimes called a calorie deficit.

Energy Input < Energy Output = Weight Loss

Example:
Calories consumed each day: 1,800
Calories burned each day: 2,050

1,800 (energy input) – 2,050 (energy output) = -250 calories

There is a negative energy balance of 250 calories. 
Over the course of a week, the body will need to burn 1,750 calories of stored fat to meet its needs, meaning you could lose approximately one-half pound of weight.