How to Start and Maintain a Calorie Deficit Diet for Weight Loss, According to Experts

How to Start and Maintain a Calorie Deficit Diet for Weight Loss, According to Experts


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In the diet world, there’s one eating plan that’s been popular for ages: The calorie deficit diet.

The diet is basic at baseline: It doesn’t tell you which foods you can and can’t eat. Instead, it just focuses on calories, which are the amount of energy that’s released when your body breaks down food. The more calories food contains, the more energy it can give your body, explains Jessica Cording, R.D., author of The Little Book of Game-Changers.

Your body needs a certain amount of calories to function normally, but when you take in more calories that you need, the excess amount is stored in your body as fat, Cording says. And, if you get rid of those extra calories, you can, in theory, lose weight.

Meet the experts: Jessica Cording, R.D., author of The Little Book of Game-Changers; Dana Ellis Hunnes, Ph.D., MPH, R.D., adjunct assistant professor at the UCLA Fielding School of Public Health; Keri Gans, R.D., author of The Small Change Diet

That’s where the calorie deficit diet comes in. But how does the calorie deficit diet work and how can you know if it’s right for you? Nutritionists break it all down.

So, what is a calorie deficit diet?

The concept behind the calorie deficit diet is pretty simple: You try to eat fewer calories than you burn. “A calorie deficit is when we consume fewer calories than our bodies burn in a day, both in terms of our natural resting energy expenditure—your natural metabolic rate—and any exercise or physical activity we engage in on top of that,” says Dana Ellis Hunnes, Ph.D., MPH, R.D., adjunct assistant professor at the UCLA Fielding School of Public Health and author of the upcoming Recipe for Survival: What You Can Do To Live a Healthier and More Environmentally Friendly Life.

Can a calorie deficit diet help you lose weight?

If you calculate things right, a calorie-deficit diet should help you lose weight. “Calories are one of the primary factors in weight gain or weight loss,” Cording says. “If somebody is consuming fewer calories than they burn, that can result in weight loss.”

So, if you typically eat 2,200 calories a day, on a calorie deficit diet, you should lose weight if you strive to cut that back to 2,000 or so calories a day.

There’s a reason why this happens. “When we take in fewer calories than we burn, our body has to get the energy from somewhere to continue its natural functioning,” Hunnes explains. “This additional energy to maintain bodily functions comes from stored energy within our own bodies.” Your body will usually burn fat first, followed by glycogen, which is what carbs are turned into in your body after you eat them, Hunnes says. And, when that fat is burned off, you end up losing weight.

How to do a calorie deficit diet

There are a few ways to go about this. “The gold standard would be to find out how many calories you burn in a day,” Hunnes says. That can include having a test done known as indirect calorimetry, which measures the amount of carbon dioxide you exhale, combined with some complicated calculations to figure out how much energy you burn at rest (i.e. when you’re just sitting there, not doing anything). There’s also something called a Bod Pod that can measure how much energy you burn at rest, but both methods aren’t easily accessible to everyone.

So, you can use online equations like the National Institutes of Health’s Body Weight Planner to try to figure out what your daily caloric intake should be in order to help you reach a certain weight goal. To use it, you enter in basic information like your height, current weight, age, and activity level, and then enter your goal weight and how much time you’d like to take to reach it. From there, the planner will give you an estimate of how many calories you should eat to hit your goal weight in the amount of time you specified and how to maintain it.

But this isn’t an exact science and it doesn’t take into account things like how much muscle mass you have (muscle tissue burns more calories than fat) and your individual metabolism, Cording says. “There are so many factors that go into energy expenditure,” she points out. Still, it can give you a rough estimate to work with.

What should your calorie deficit be?

If you have a goal of losing about a pound a week, you can try to slash 500 calories from your existing dietary intake, says Keri Gans, R.D., author of The Small Change Diet. “Safe weight loss is considered at a rate of one pound per week lost,” she says. “One pound is equivalent to about a 500-calorie deficit per day for one week.”

But being able to cut that many calories and feeling comfortable with it depends on what you were eating before, Cording says. If you had plenty of high-calorie processed foods and sweets in your diet, swapping them out in favor of plenty of fruits and vegetables, lean proteins, and healthy fats may not feel like a huge deal in terms of your hunger levels, she says. If you were already following a nutritious meal plan, though, you may feel more comfortable cutting out 125 to 250 calories a day instead, with the understanding that it will likely take a little longer for you to lose the weight. “I’ve seen people do really well with that,” Cording adds.

How much of a calorie deficit is too much?

The Academy of Nutrition and Dietetics recommends that adult women have between 1,600 and 2,400 calories a day, while men should strive to have between 2,000 and 3,200 daily calories. (The lower end is if you do little to no activity every day.) Dropping below the minimum amount is not considered healthy, so you’ll want to be mindful of having too much of a calorie deficit.

You also could be having too much of a calorie deficit if the pounds you’re losing are “adding up too quickly, such as five pounds per week or more,” Gans says. Symptoms like fatigue, nausea, dizziness, and constipation can also be signs that you’ve gotten too overzealous with your weight loss pace, she says.

In general, Hunnes says, “I strongly encourage not cutting out more than 15 to 20% of calories.”

What can you eat on a calorie deficit diet?

Technically, you can eat anything on a calorie deficit diet—as long as you eat in a deficit, Cording says. “But, that said, whatever you’re eating needs to end up being less than the energy you expend,” she says.

Do macronutrients matter?

Macronutrients are proteins, fats, and carbohydrates—these nutrients are what contribute to the caloric value of the foods you eat. Certain diets value individualized macronutrient ratios over a simple calorie deficit approach, which can be helpful for some health and fitness-related goals. But when it comes to weight loss “macronutrients do not matter as much as overall calories,” Gans explains.

“However, one should consider not cutting back as many calories from nutrient-rich foods, especially those that aid in satiety, such as fiber and protein,” Gans adds. “Instead, consider cutting back on foods that are packed with added sugars and sodium, and provide minimal nutrition.”

What should you eat on a calorie deficit diet?

While you can eat whatever you want on a calorie deficit diet and still follow the “rules” of this eating plan, Cording says you’re likely to have the most success if you focus on nutrient-dense foods.

“You want to make sure you’re getting a lot of vitamins and minerals, along with adequate protein, health fat, and fiber,” she says. “That’s step one.”

But Cording also recommends that you “pay attention to blood sugar management” by getting a good balance of protein, fat, and carbohydrates at every meal and snack. This, she says, will help you feel fuller, longer, and can help you bypass blood sugar crashes that will leave you feeling hungry and cranky.

“A hundred calories of white bread is going to feel very different from 100 calories of fish or avocado,” Cording points out.

What’s a good way to cut excess calories from your diet?

Sure, you could just eat less than what you were having in the past, but Cording says a little extra thought and planning can help you feel less deprived on a calorie deficit diet.

“What I’ve found works really well for a lot of people is taking an honest, nonjudgmental look at your diet and getting a sense of if you’re having extra calories that are coming from foods that don’t provide much in the way of nourishment,” she says. This approach, Cording says, “gives you a clue of what foods to put on the ‘moderation’ list.”

Some typical easy ways to cut calories, she says, include ditching or cutting back on the following:

  • Bars

  • Cereals

  • Yogurt

  • Alcohol

  • Soda

It’s also important to pay attention to portion sizes, Cording says. “That can make a big difference for people,” she says.

What’s the healthiest way to do a calorie deficit diet?

In addition to not cutting out too many calories from your daily diet, experts say there are some other tips that can help you do a calorie deficit diet in a healthy way:

  • Focus on what you’re adding to your diet. “If you are adding more fruits and veggies to your diet, you might naturally wind up eating less foods with lots of added sugar and fat,” Gans says. “Therefore, you will lose weight.”

  • Strive for nutrient-rich foods. Those include fruits, vegetables, 100% whole grains, low-fat dairy, seafood, poultry, lean meats, and healthy fats, Gans says.

  • Minimize processed foods. “I recommend incorporating the most natural forms of foods into your diet as possible— single-ingredient, as close to nature as can be found foods,” Hunnes says. “The fewer things out of a package the better.”

  • Watch your portion sizes. While you could calculate exact calories at every meal, that can get stressful and time-consuming. “Keeping portion sizes in check is most likely one of the best tools to help,” Gans says.

  • Pay attention to your macronutrients. Macronutrients, aka “macros,” are the main components of food that you need to be healthy, Cording explains. “Make sure you’re getting enough protein, healthy fats, and calories that feels good to you,” she says.

  • Eat in. “Eating at home gives you greater control over what is in your food,” Hunnes says.

Should you exercise while cutting calories?

While cutting calories from your diet might be enough to reach your health or weight goals, “staying active is always a good idea no matter what,” Gans explains. Plus, “the more muscle you build, the more calories you may burn, even at rest.”

According to the Centers for Disease Control and Prevention (CDC), adults should strive to get 150 minutes of moderate-intensity physical activity plus two days of strength training per week. And there are a slew of overall health benefits associated with exercise, like increasing your life span, helping to treat anxiety and depression, and lowering the risk of cancer.

How hard is it to follow a calorie deficit diet?

It really depends on what your dietary habits were like in the past, Cording says. If you weren’t the healthiest eater and you’re ready to make a change, it may not be that hard to cut excess calories out of your life, she says.

But, she adds, it’s really important to take things slow and not get too excessive with the amount of calories you cut. “I wouldn’t recommend being overly restrictive,” she says. “Some people will resort to 1,200 calories—that’s what you’d give a toddler.” If you currently take in 2,500 calories a day, Cording suggests starting with 2,200 calories a day and seeing how you feel, along with what kind of results you get. If it’s doable, you may be able to get down to 2,000 calories a day. “I just don’t recommend starting with a huge deficit,” she says.

If you’re interested in doing a calorie deficit diet and aren’t sure where to start, check in with your primary healthcare provider or a registered dietitian—they should be able to help offer personalized guidance.

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