What Is a Calorie Deficit? How It Impacts Weight Loss

You may have heard the saying “calories in versus calories out” when it comes to weight loss. This is referring to a calorie deficit. But what is a calorie deficit, exactly?

Basically, you need to take in fewer calories than you burn to lose weight.

While it’s true that a caloric deficit helps drive weight loss, it’s not the only thing. Rather than striving to start a calorie deficit, we recommend taking the spotlight off calorie counting and opting for a more holistic approach.

Still, using trusted online calculators to learn about your energy needs can come in handy and may help lead to healthier choices.

We’ll dig into what it means to create a calorie deficit to lose weight and other critical factors of healthy, sustainable weight management.

A calorie deficit essentially means eating fewer calories than your body burns. In more technical terms, it’s the state in which your energy intake is lower than energy expended (also known as total daily energy expenditure — TDEE, for short — which we’ll explain in more detail shortly).

A calorie deficit prompts your body to tap into stored energy reserves — primarily fat — to make up for the shortfall. This is what ultimately leads to weight loss.

Creating a calorie deficit is a factor in many weight loss strategies, whether through changes in nutrition, increasing daily activity, or a combination of both. There are healthy ways to approach it, but remember, it’s not everything.

Why We Don’t Recommend Calorie Counting

Obsessing over the amount of calories you eat makes weight loss — and eating, in general — an unsustainable chore. What’s more, it can have lasting negative effects on mental health.

Food should provide nutrition while bringing you joy.

We’d argue that it’s more crucial to have a general idea of your daily energy needs. Instead of counting calories, focus on mindful eating, making nutrient-dense food choices, practicing portion control, and listening to your body.

These skills — paired with exercise and other healthy lifestyle habits — work together for healthy weight management. Plus, you can keep using them in your everyday life even after reaching an initial weight loss goal.

As for how to do a calorie deficit — or if you’re wondering what calorie deficit is recommended for weight loss — you can aim to get 300 to 700 calories below your estimated needs. This is typically recommended as a healthy calorie deficit for weight loss. But, again, it varies for everyone.

Wondering, How many calories do I need a day? or What is a healthy calorie deficit for me? You’ll need to do some math (or use an online calculator).

Let’s go over how these calculations work.

Your body’s needs are going to be different from someone else’s. Learning how to calculate those needs with science can help you reach a point where you’re neither getting too much nor too little food.

When all’s said and done, online calculators can help you figure out these details without having to do the math yourself.

You can use a formula that accounts for your basal metabolic rate (BMR) — your daily energy expenditure at rest — and your activity level.

There’s no shortage of online calculators for BMR, but not all are created equal. The Harris-Benedict equation is often used to estimate BMR based on gender, age, weight, and height. Once you have your BMR, multiply it by an activity factor to determine your total daily energy expenditure (TDEE).

TDEE is the number of calories your body burns a day (aka daily calorie burn). You can also think of it as how many calories you need to maintain your current weight based on your activity level. From there, you can adjust your calorie intake to create a deficit for weight loss.

For instance, let’s say your BMR is 1,800. If you’re moderately active, your activity factor might be 1.2. Multiple 1,800 by 1.2 to get your TDEE, which would be 2,160. To create a 500-calorie deficit, you’d want to aim to eat 1,660 a day.

Is a calorie deficit healthy? It depends. A calorie deficit can be an effective tool for weight loss, but it’s not without its risks.

When considering how to go on a calorie deficit, don’t overlook the potential risks for:

• Nutrient deficiencies. Eating fewer calories or following very low-calorie diets may lead to an inadequate intake of certain vitamins, minerals, and protein.

• Muscle loss. In severe or prolonged deficits, your body can start breaking down muscle tissue for energy, leading to a loss of lean muscle mass and reduced strength.

• Decreased bone density. Inadequate calorie intake, along with low calcium and vitamin D intake, can increase the risk of bone fractures over time.

• Reduced metabolism. Ongoing calorie deficits can slow down your energy burn. This can make losing weight or maintaining weight loss more challenging. 

• Fatigue and weakness. When you’re not eating enough calories to sustain your energy, you’re more likely to feel tired. This can impact your mental performance and ability to be physically active.

• Hormonal imbalances. Calorie deficits can disrupt hormones, especially those involved in metabolism, appetite, and reproductive functions.

• Impaired immune function. Inadequate calorie intake can weaken immunity, making you more likely to get sick.

• Mental health effects. Ongoing calorie restriction could probably make anyone irritable. Not eating enough can lead to mood swings and increase stress.

• Disordered eating. Unsustainable calorie deficits could end up making someone overeat from hunger or cravings for restricted foods, potentially leading to long-term mental health issues.

Risks of Eating Too Few Calories

Is a calorie deficit safe? It depends on the circumstances. There’s often a focus on how not to overeat calories, but not eating enough calories is also problematic — perhaps even more so.

Eating too few calories can pose risks to your physical and mental health. Severely restricting calories can eventually lead to nutrient deficiencies and side effects like weakened immunity, fatigue, brain fog, or trouble concentrating.

It can also result in muscle loss and a slowed metabolism, making it harder to maintain a healthy weight and reach your weight loss goals. Finally, extreme calorie restriction can contribute to an unhealthy relationship with food.

Sustainable weight loss goes far beyond a calorie deficit. Rather than counting calories, we recommend prioritizing nutrient density (like high-fiber and high-protein foods), mindfulness of portion sizes, and the quality of the foods you’re eating. In other words, aiming for a healthy, balanced diet.

Some healthy foods to incorporate into your meals and snacks:

• Lean proteins

• Whole grains

• Fruits

• Vegetables

• Nuts and seeds

Nutrition is a vital component of healthy weight management that’s often overlooked when the focus becomes calories.

Besides nutrition, we suggest focusing on four factors for healthy weight loss:

• Being active

• Staying hydrated

• Getting enough high-quality sleep

• Considering weight loss medication, if necessary

Keep scrolling for more tips and insight.

1. Movement

Exercise has countless benefits, such as improved mood and a lower risk of things like heart disease, type 2 diabetes, and certain cancers. It’s important for weight loss because it helps create a calorie deficit by raising your energy expenditure.

Regular physical activity boosts metabolism so you keep burning calories even after a workout. Exercise also helps preserve lean muscle mass while you burn excess body fat.

Researchers recommend a minimum of 150 minutes of moderate-intensity exercise or 75 minutes of vigorous-intensity aerobic exercise per week, plus resistance training at least twice a week for general health. For weight loss, this goes up to 200 to 300 minutes a week.

But these are just recommendations. It’s okay to start where you’re at and fit what you can into your schedule.

Find enjoyable ways to move your body that you can do long-term, like: 

• Jogging with your dog

• Walking around your neighborhood after dinner

• Playing basketball or soccer with friends

• Joining a group fitness class

• Lifting dumbbells or using weight machines and resistance bands for strength training

Remember, all movement counts.

2. Hydration

Hydration is essential for wellness. It supports bodily functions involved in metabolism, fat loss, and digestion.

Drinking water, especially before meals, can also help curb your appetite and prevent overeating. Stay hydrated during and after exercise to replenish fluid stores and support energy expenditure.

Keep a reusable water bottle with you to sip throughout the day. If you get bored of plain water, flavor it with lemon or cucumber slices. Or opt for unsweetened seltzer water or herbal teas sometimes.

3. Sleep

Better sleep supports sustainable weight loss by regulating hunger and appetite hormones like leptin and ghrelin.

Experts recommend adults get seven to nine hours of sleep nightly. To improve your sleep, try:

• Creating a sleep-promoting environment in your bedroom, using things like comfy PJs, breathable bedding, blackout curtains, and white noise if needed

• Avoiding technology close to bedtime, as the blue light emitted from screens disrupts melatonin production and can make it harder to doze off

• Going to bed and waking up around the same time every day

Adequate shut-eye helps restore energy levels for the next day’s activities. It also improves brain function and decision-making abilities.

Moreover, sleep deprivation is associated with increased energy intake (i.e., eating more because your hunger hormones are out of whack).

4. Weight Loss Medications

Not everyone loses weight from diet and exercise alone. Genetics and health conditions can make weight loss more difficult for some.

Many people with obesity or overweight may benefit from extra support to jumpstart the process. That’s where medications come in.

Combined with nutrition, exercise, and other healthy lifestyle habits, weight loss medications can be a helpful tool.

Some suppress appetite by targeting brain chemicals and reducing hunger. Others might increase calorie expenditure by boosting metabolism or limiting how much fat or carbs your body absorbs.

Some of the most effective weight loss medications include:

• Glucagon-like peptide-1 agonists. GLP-1 weight loss drugs mimic the action of GLP-1, a naturally occurring hormone that regulates appetite and glucose metabolism. They decrease appetite, slow digestion, and increase satiety. Examples include semaglutide (Wegovy®, Ozempic®) and liraglutide (Victoza®).

• Topiramate. Topiramate helps with weight loss by reducing appetite and increasing feelings of fullness. It might also affect certain brain chemicals involved in regulating food intake and metabolism, ultimately contributing to decreased calorie consumption.

• Metformin. This medication is primarily prescribed to manage type 2 diabetes. By helping the body use insulin more effectively, metformin may decrease hunger and promote modest weight loss over time.

• Contrave®. This is a combination of bupropion (an antidepressant) and naltrexone (a drug used for alcohol and opioid dependence). It reduces appetite and cravings by targeting reward centers in the brain.

To find out if weight loss medications might be an option for you, take our free online assessment. If you’re a good fit, you’ll get a customized treatment plan from a healthcare provider.

We’ve rounded up some of the most commonly asked questions about calorie deficits.

How Many Calories Do You Naturally Burn in a Day?

The number of calories burned naturally in a day depends on factors like age, gender, weight, and physical activity level. On average, an inactive adult may burn around 1,600 to 2,400 calories a day, while those with higher activity levels can burn more.

How Much of a Calorie Deficit Does a Person Need to Lose 1 Pound?

When it comes to how many calories to eat to lose weight, everyone is different. To lose one pound of body weight, you typically need to create a calorie deficit of roughly 3,500 calories. This can be achieved through reducing calorie intake, increasing physical activity, or both.

Also, keep in mind the average calorie intake for men can be different from calorie intake for women. As noted, caloric intake by age can vary too.

How Much of a Calorie Deficit for Weight Loss Is Safe?

The safety of a calorie deficit for weight loss depends on things like your starting weight, overall health, and unique nutritional needs. In general, a gradual calorie deficit of 500 to 600 calories a day is considered safe and sustainable for most people, leading to a weight loss of about one to two pounds a week.

What is a calorie deficit? Creating a calorie deficit is a factor in weight loss because, in order to lose weight, your body has to be taking in fewer calories than it’s burning.

If you’re starting a weight loss journey and considering how a calorie deficit fits into it, keep these things in mind:

• Weight loss is more than just calories. We all have general calorie needs to lose weight — but this isn’t the only piece of the puzzle. The nutritional quality of your meals and snacks, exercise routine, sleep habits, and hydration are also important. Rather than being laser-focused on calorie intake, we recommend a holistic approach for sustainable, safe weight loss that incorporates these other key components.

• Getting too few calories also poses risks. There’s often a focus on eating more calories than you need. However, eating too few calories can be dangerous, posing numerous health risks. Not only can it prevent you from getting the nutrients you need, but it can also leave you fatigued and irritable — and eventually, it might alter your metabolism in a way that leads to a weight loss plateau.

• Don’t be afraid to ask for help. Weight loss is personal. We all have different needs, preferences, and challenges. It can be overwhelming to develop a weight loss plan on your own. Reach out to a healthcare provider for support, or meet with a registered dietitian nutritionist who can help create a nutrition plan that works for you.

Curious about what a personalized weight loss plan might look like for you? Start by taking our free weight loss assessment.