How to Safely Use a ‘Calorie Deficit’ To Lose Weight

Losing weight is all about numbers — and we’re not just talking about pounds. That’s because the formula for weight loss typically comes down to burning more calories than you’re eating, a math equation called a “calorie deficit.”

We asked registered dietitian Beth Czerwony, RD, LD, how to make the process add up to a slimmer and trimmer you.

What is a calorie deficit?

A “calorie deficit” means that you’re taking in fewer calories through food and drinks than your body burns during the day. There are basically two ways to work the numbers to create a calorie deficit.

• Reduce your daily calorie intake below what you burn.
• Increase your calorie burn above what you take in.

But getting to that point of action is a process: “If you want to use a calorie deficit to lose weight, I suggest tracking the calories you’re currently eating and burning before making any changes,” says Czerwony. “It’s good to understand your starting point.”

Using a calorie deficit to lose weight

A daily 500-calorie deficit should allow you to lose about 1 pound per week. That may not sound like a lot in an instant-results sort of world, but Czerwony notes that slower weight loss is more likely to stick in the long term.

It’s also easier for your body to adjust to a smaller calorie deficit than a larger one. (Nobody wants to feel hangry, right?)

“Eating 500 fewer calories per day is a good place to start if you’re looking for weight loss,” notes Czerwony. “You can also do a smaller reduction in calorie intake — 200 or 300 calories a day — combined with an increase in exercise that burns more calories.”

And even with a 500-calorie deficit, it can take your body time to adjust. You may not lose any weight for the first week or two.

“If you do lose weight in the first week, you’re probably dropping water weight,” she explains. “This is usually due to cutting some of the junkier carbs and salt from your diet. After that, the fat loss begins.”

How to calculate calorie deficit

To do your calorie deficit math, it helps to know your body’s daily calorie requirements. Basically, you’re looking for a basic measurement of how many calories you typically burn in a day.

Czerwony prefers the Mifflin-Saint Jeor formula for calculating daily calorie fueling needs. The formula considers factors like your height, weight, sex, age and activity level to come up with a total.

Once you know your daily calorie requirement, subtract your target calorie deficit from that number to get your new calorie intake goal.

So, if your daily calorie need is 2,000 calories and you want a 500-calorie deficit for weight loss, your new calorie-intake target would be 1,500 calories a day. (To show the math: 2,000 – 500 = 1,500).

Are there risks to running a calorie deficit?

Taking in fewer calories than you burn can lead to some unpleasant side effects. A high calorie deficit can lead to issues like:

• Fatigue
• Nausea
• Dehydration
• Constipation
• Headaches
• Crabbiness

And if you have existing health conditions, running a calorie deficit may bring unexpected complications. Subtracting from your diet can affect blood sugar levels, blood pressure and fluid levels.

“You can harm yourself with a calorie-deficit diet in certain situations,” warns Czerwony.

Take extra caution if you have:

• Type 2 diabetes
• Kidney problems
• High or low blood pressure
• Eating disorders

“It’s best to talk to your healthcare provider before starting a calorie-deficit diet for weight loss,” says Czerwony. “They can work with you to set up a program that keeps you safe while meeting your goals.”

Does a calorie deficit guarantee weight loss?

It seems logical that you should see results on the scale if you’re burning more calories than you’re eating. But changes to your metabolism could prevent weight loss even with a calorie deficit, notes Czerwony.

Outside factors that might impact your metabolism include:

• Medications
• Poor sleep
• Stress
• Hormonal changes (like menopause)
• Underlying health conditions

In addition, cutting too many calories from your diet may slow your metabolism as your body works to conserve resources. That can make it more difficult to lose weight even as you’re eating far less.

Tips to see results from a calorie deficit

So, what can you do to improve your chances of achieving a calorie deficit and melting away a few pounds? Czerwony offers these suggestions.

• Stay hydrated. Sometimes, what feels like hunger is actually your body signaling thirst. Drinking plenty of water also helps your body adjust to taking in fewer calories.
• Get enough protein. Eating protein is beneficial on multiple levels. For one, it can limit total calorie intake by making you feel fuller. But it’s also critical for maintaining muscle mass that keeps your metabolism firing.
• Focus on fruits and veggies. Aim to eat five servings of fruits and vegetables per day to meet your vitamin and nutrient needs. A bonus? The bulk and water in the plant-based foods can help keep you from feeling hungry.
• Take a multivitamin. A multivitamin can fill in any nutrition gaps that might develop as your cutting calorie consumption. Talk to your healthcare provider about what supplement might be right for you.

Also, know that you’re not alone in your weight-loss journey. Talk to a healthcare provider for advice or encouragement.

“Weight loss can be complex and difficult even if you’re doing everything right when it comes to maintaining a calorie deficit,” supports Czerwony. “Ask questions. There’s no reason to go at it alone.”