If you’ve ever tried to lose weight, you’ve probably heard about the importance of a calorie deficit — but what does that mean?

Being in a calorie deficit simply means “you eat fewer calories than your body uses,” explains Dana Hunnes, PhD, MPH, RD, a senior dietitian at the Ronald Reagan UCLA Medical Center.

You can be in a slight calorie deficit or a significant calorie deficit, depending on how many calories you remove from your diet, says Emily Tills, MS, RDN, CDN.

Of course, that’s not as easy in practice as it is in theory, as you already know if you’ve ever tried to reduce your calorie intake. And if you run a calorie deficit long enough, Tills adds, your body may metabolically adapt to conserve energy.

Here’s what you need to know about creating a calorie deficit and avoiding potential pitfalls.

How Many Calories Do You Need to Eat Each Day?

Before you can create a calorie deficit in your diet, you’ll need to figure out how many calories your body needs each day to maintain your current weight.

According to the Dietary Guidelines for Americans, the average sedentary man between ages 21 and 50 needs between 2,200 and 2,400 calories per day. The average sedentary woman in the same age range needs between 1,800 and 2,000 calories per day.

However, the exact number of calories needed to lose or maintain weight is individual to you. It can be influenced by several factors, including muscle mass, fat mass, nutrition and dieting history, and overall health history, Tills says.

You don’t have to figure out all of those things alone. “There are predictive equations that can be used to approximate how many calories we need in a day,” Hunnes explains.

One good example is the National Institute of Health’s Body Weight Planner, which factors in your sex, height, current weight, and activity level. But while this can be a useful tool, your best bet is to consult with a registered dietitian who can give you their professional opinion and a personalized plan.

Once you have this number, figure out how close to or far from it you are by tracking what you’re eating and drinking for a week. From there, you can calculate how many calories you’ll need to cut from your typical eating plan each day to run a calorie deficit.

How Do You Run A Calorie Deficit?

According to Hunnes, you can run a calorie deficit in three different ways: through diet alone, through exercise alone, or through a combination of the two. (If you’re relying on exercise for part of your calorie deficit, be aware that we often overestimate calories burned during exercise, and cardio machine calculators aren’t always accurate.)

“Start with a mild deficit of 200 to 300 calories to help with fat loss and weight loss,” Tills suggests. For example, if you’re currently eating 2,000 calories per day, start your calorie deficit by aiming for 1,700 to 1,800 calories instead.

If you’re on the heavier side, you may be able to start with a more significant calorie deficit, Hunnes says.

However, before starting anything, consult with a registered dietitian and your doctor — and be sure you’re not under-eating so much that it takes a toll on your health.

The next step is to decide how long you plan to run a calorie deficit. Tills recommends setting a time-based goal — for example, you might plan to run a calorie deficit for four months, followed by a one-month break at maintenance calories.

This can be more helpful than a weight-based goal (“I’ll run a calorie deficit until I hit my goal weight”) because a weight-based goal doesn’t take into account any muscle mass you gain or hormonal fluctuations you experience along the way.

Even when running a calorie deficit, it’s normal for your weight loss to stall at a certain point. “Many people plateau at some point during their weight loss as their bodies adapt to a new energy intake,” Hunnes explains. If this happens, reassess the baseline of how many calories you need per day. When you lose weight, your body needs fewer calories, so you may need to recalculate how many calories you need to lose weight.

7 Ways to Decrease Your Calorie Intake

When you’re just starting out with a calorie deficit, you want to go for low-hanging fruit. That means prioritizing the easiest ways to decrease calories first. Here are seven simple tactics to help you run a calorie deficit.

Remove added sugar from your diet.
Cut back on “liquid calories” from juice, soda, and alcohol.
Measure out cooking oils. (These contain around 120 calories per tablespoon!) Or use a cooking spray instead, such as this avocado oil spray.
Bake, grill, or steam foods instead of frying them.
Use smaller portions of calorie-rich toppings like mayo, sour cream, and guacamole, and be more mindful when eating these sauces.
Swap in reduced-fat versions of dairy products.
Choose leaner cuts of meat.