Calorie-deficit diets can be effective but it's not for everyone, according to dietitians

• Being in a calorie deficit can be an effective way to diet but it's not a long-term solution.
• Benefits include weight loss, improved cardiovascular health, and reduced risk of chronic disease.

Nobody likes to diet but in the pursuit of losing a few pounds, eating in a calorie deficit is a tried-and-true way to get the job done. Research shows that a person's risk of obesity is determined by their total calorie intake and that putting your body in a calorie deficit for a consistent period of time can result in weight loss. But this form of restrictive eating has gotten some flack for being unsustainable — and unhealthy.

So, what exactly is a calorie-deficit diet, and is it a safe way to lose weight? I spoke with a few registered dietitians to get the lowdown on this eating style so you can determine if it's the right move for you.

What is a calorie-deficit diet—and how do you do it?

Calorie-deficit diets are exactly what they sound like: eating fewer calories than your body burns each day. It can be done in a variety of ways, including reducing portion sizes, eating low-calorie foods, and increasing physical activity.

Personal trainer and registered dietitian, Jesse Feder, says that while the amount of calories you need to burn depends on the person, the essence of the diet remains the same.

"If you burn 2,000 calories in a day, a caloric-deficit diet would have you eating less than 2,000 calories," he says. "The exact calorie intake will typically be around 1,500 to 1,700 calories per day, so the deficit would be 500 to 300 calories."

Feder says that several factors contribute to the number of calories an individual needs, including age, current weight, height, activity level, metabolic rate, and weight loss goals.

Here's how many calories certain folks might need each day, according to Feder:

When working with clients, Feder typically recommends a 250- to 500-calorie deficit, as this results in a steady and sustainable rate of weight loss over time. "I aim for a range that's not too drastic of a change that's hard to maintain," he says, adding that "it's just enough to make a difference in body weight."

Determining your own personal calorie deficit can be accomplished by working with a dietitian or adding your specifications to an online calorie deficit calculator such as the one offered by the National Academy of Sports Medicine. Apps like My Fitness Pal and LoseIt can also be helpful in finding your deficit and tracking your daily calorie intake.

Just don't reduce your food intake too much. Research shows that 1,200 to 1,500 daily calories for women and 1,500 to 1,800 daily calories for men is a suitable and healthy amount for sustainable weight loss. However, these numbers are not a catch-all for everyone. As mentioned above, daily calorie needs differ person-to-person. Always chat with your doctor before cutting your calories.

What kind of food can you eat?

One big appeal of a calorie-deficit diet is the notion you can eat whatever you want so long as you stay within your daily calorie limit. However, the old adage "a calorie is a calorie" isn't quite true. After all, 100 calories of broccoli are going to affect your body differently than 100 calories of chocolate.

Feder encourages his clients to choose nutrient-dense foods over any high-processed meals and snacks.

"Unhealthy foods are usually higher in calories," he says, adding that filling up on those items means you'll likely have to eat even less food to stay within your limit, which can be difficult to sustain.

"This is why it's much better to have lean proteins, whole grain carbohydrates, healthy fats, and a lot of fiber," he says. "These foods are typically lower in calories when compared to other foods."

Research also shows that eating a lot of refined carbs (commonly found in junk food and fast food) can contribute to more frequent hunger while eating protein helps you feel fuller longer.

That's why Feder suggests focusing on high-protein foods like beans, oats, yogurt, white meat chicken, turkey, vegetables, fruits, nuts, and seeds.

What are the benefits of a calorie-deficit diet?

Some of the scientifically backed benefits of eating in a calorie deficit include:

• Weight loss: According to multiple studies, calorie-deficit diets can be effective for both short and long-term weight loss. However, you will need to adjust your calorie intake as you lose weight to ensure continuous progress and to be able to sustain the weight you've lost.
• Reduced risk of chronic diseases: A study done in 2019 found evidence that cutting just 300 calories a day may significantly improve cholesterol, blood sugar levels, and blood pressure. All of which can reduce the risk of chronic diseases such as diabetes and heart disease. However, it's important to note that this result was only observed when combined with a relatively healthy diet.

What are its drawbacks?

Despite some potential benefits, calorie-deficit diets do come with a few drawbacks. These include:

• Slowing your metabolism: Eating in a calorie deficit may cause your metabolism to slow down, even after you start eating in a calorie surplus. This can make it harder to keep off the weight you've lost and may even increase your risk of gaining it back.
• Nutritional deficiencies: Restricting your calories — and carbs — means you may potentially miss out on key nutrients and vitamins your body needs to stay healthy.
• Lowers immunity: Eating too few calories can also lead to a weakened immune system, as your body isn't receiving the nutrients it needs to function. One study of women with obesity found that restricting calories reduced microbial defense cells.

Is it a long-term diet?

The short answer is no. Registered dietitian, Jenn Baswick, says that restrictive diets like being in a calorie deficit are not sustainable in the long term because being "physically undernourished" and "mentally deprived" can cause people to quit after a certain period of time.

"Both of those things can lead to almost a rebound-type of effect that brings people to eat more after not being able to keep up with a calorie deficit," she says. For her, the answer is clear: "Restrictive dieting just doesn't work for the large majority of people."

Beyond just not being sustainable, calorie-deficit diets can be downright dangerous, according to Baswick — especially if you restrict calories for too long.

"The biggest danger in my eyes, as someone who has worked with folks who've tried diets like this for years, is that any form of restrictive dieting can lead to disordered eating and even potentially eating disorders," she says. "Trying to maintain a calorie deficit can lead to having a very poor relationship with food."

Insider's takeaway

In the pursuit of weight loss, it's easy to see why calorie-deficit diets are appealing. However, it's not a sustainable way of eating and can come with a number of risks, including nutritional deficiencies, slowed metabolism, and even disordered eating. While it's possible to find success with this diet in the short term, it's not a healthy and safe long-term dieting strategy.

If you want to make permanent lifestyle changes, consider talking to a registered dietitian for help. They can create an individualized nutrition program that can fit your needs and goals, plus provide support and guidance to help you stay on track.