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If you want to lose weight, you've probably heard the term "calorie deficit" more than once. But what does it actually mean, and how do you figure out yours? Here's everything you need to know.
What Is a Calorie Deficit?
A calorie deficit happens when you burn more calories than you eat. Your body needs a certain amount of energy every day just to function. When you consistently consume less than that, it starts pulling from fat stores to make up the difference. That's how weight loss happens.
The opposite is also true. Eat more than you burn, and your body stores the excess as fat. It really is that simple.
How Many Calories Do You Actually Need?
This is where people get confused, because the answer is different for everyone. Your daily calorie needs depend on your age, gender, height, weight, and how active you are. A 35-year-old woman who works a desk job burns significantly fewer calories than a 25-year-old man doing physical work all day.
To get a starting number, most calculators use one of two formulas.
The Harris-Benedict formula has been around since 1918 and is still widely used:
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Women: 655.1 + (4.35 x weight in lbs) + (4.7 x height in inches) - (4.7 x age)
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Men: 66.47 + (6.24 x weight in lbs) + (12.7 x height in inches) - (6.8 x age)
The Mifflin-St. Jeor's formula is newer, and many nutrition professionals now prefer it, partly because it better accounts for today's more sedentary lifestyles:
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Women: (4.536 x weight in lbs) + (12.7 x height in inches) - (4.92 x age) - 161
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Men: (4.536 x weight in lbs) + (12.7 x height in inches) - (4.92 x age) + 5
Both give you your basal metabolic rate, which is the number of calories your body burns at rest. From there, you multiply by an activity factor to get your total daily needs.
Let's make it real numbers. For a 32-year-old woman, 5’5” tall, 150 lbs. Using Mifflin-St. Jeor:
(4.536 x 150) + (12.7 x 65) - (4.92 x 32) - 161 = 680.4 + 825.5 - 157.44 - 161 = 1,387 calories at rest.
Now consider a 35-year-old man, 5’10” tall with a weight of 180 lbs:
(4.536 x 180) + (12.7 x 70) - (4.92 x 35) + 5 = 816.48 + 889 - 172.2 + 5 = 1,538 calories at rest.
These are resting numbers only. To find out how many calories you actually burn in a day, you multiply by an activity factor:
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Sedentary (little or no exercise): x 1.2
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Lightly active (1-3 days of exercise per week): x 1.375
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Moderately active (3-5 days per week): x 1.55
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Very active (hard exercise 6-7 days per week): x 1.725
So, that same woman, a desk worker with light exercise three times a week, would multiply 1,392 by 1.375 to get roughly 1,907 calories per day. That's what her body needs to maintain her current weight. If she regularly eats less than that, she’s in a deficit.
How Big Should Your Deficit Be?
If you're short by 500 calories a day, you'll lose about half a kilogram of fat every two weeks. It's a common and reasonable goal for a healthy, gradual weight loss.
It is not advisable to consume less than 1,200 calories per day for women or 1,500 calories per day for men. Your body requires sufficient fuel to support muscles and organs and to maintain basic energy. Crash diets are difficult to maintain and can result in fat and muscle loss.
If you follow a moderate deficit with enough protein, then you have the greatest chance of maintaining the weight loss.
Two Ways to Create a Deficit
Eat less, move more, or do both.
The easiest ways to cut back on intake are to cut portions, steer clear of liquid calories, and limit intake of processed foods. Little things do add up. If you replace a large sweetened coffee with a black coffee, you will save 300 to 400 calories without making any other changes.
On the movement side, an extra 30 to 45 minutes of brisk walking each day will burn an additional 150 to 250 calories, depending on your weight. Strength training is also helpful since muscle burns more calories at rest than fat. The more muscle you have, the more calories you burn at rest.
Where Meal Prep Fits in
The challenge for people who cook from scratch every day is that it's very difficult to stick to a calorie goal when eating. Serving sizes differ, recipes adjust, and it's easy to underestimate how much is on your plate.
That's where a service like Ideal Nutrition comes in handy. Our menu includes more than 40 meal options to choose from, and each one is checked for nutritional accuracy by an executive chef team, so you can be sure of what you are eating.
We use fresh, locally grown ingredients - there are no artificial colors added. The containers are BPA-free and made from recycled materials. If you're looking for a meal prep service that will help you reach your daily calorie goal without spending hours in the kitchen, Ideal Nutrition is right for you.
What About Muscles?
One of the best long-term strategies is to build muscle while losing fat. The more muscle mass you have, the more calories you burn at rest. When you're lifting weights and following a moderate deficit, you're on two fronts at once.
Frequently Asked Questions
What does calorie deficit mean?
It means that you are eating less than your body burns in a day. This, when maintained over time, leads to fat loss.
How do I calculate my calorie deficit?
First, determine your basal metabolic rate (BMR) with the Mifflin-St. Jeor or Harris-Benedict formula. To find your total daily energy expenditure, multiply your activity level. Take 300-500 calories off of that amount to determine your deficit goal.
How fast will I lose weight with a 500-calorie deficit?
Roughly 1 pound of fat every two weeks, assuming the deficit stays consistent.
Can I create a deficit through exercise alone?
Yes, but it is more difficult to maintain than combining diet and exercise. It is easier for most people to reduce 300 calories from their diet and burn an extra 200 calories through their exercise routine than it is to exercise off the full 500.
Is a bigger deficit better?
Not necessarily. Extremely high deficits can lead to muscle loss, nutrient deficiencies, and burnout. A moderate and steady deficit is more effective in the long run.
