How to Figure Out Exactly How Many Calories You Need to Lose Weight, According to a Nutritionist

This simple trick cuts the confusion.

Now that January is well underway and new year resolutions have been made, many of us are vowing to save more money, get enough sleep, and, you guessed it, get healthier or feel better by losing some weight. Shedding extra pounds is always a top resolution shared by millions of people. If it's yours too, one question is likely running through your mind: How many calories should I actually take in every day if my goal is to lose weight?

On average, a moderately active woman between the ages of 26 and 50 should take in about 2,000 calories per day to maintain a healthy weight, according to the USDA's Dietary Guidelines for Americans. But when it comes to weight loss, calories aren't a one-size-fits-all thing. How many to consume depends on factors like your age, height, sex, and activity level.

If you've Googled this question, you've probably seen weight loss websites or apps that use a formula taking these variables into account. After you've entered your personal data, voila—it spits back the magic number of calories you need daily to reach your desired healthy weight. Sound too good to be true? Health contributing nutrition editor Cynthia Sass says it probably is.

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How Weight Loss Apps Calculate Daily Intake

When you sign up with a weight-loss app like MyFitnessPal, for example, you'll be asked a number of specific questions to help the app set goals for you: your current weight, height, goal weight, sex, age, activity level, and the speed at which you want to lose weight (anywhere from one half to two pounds per week).

Sass says most of these apps use a formula that calculates the number of calories you need to maintain your current weight, and then it subtracts 500 calories per day if you want to lose one pound per week (or subtracts 1,000 per day if you want to lose two pounds per week). If you think that sounds like a huge number of calories will be cut from your daily meal plan, you're right. "The problem is that it will reduce calories below what is needed for someone to achieve and stay at their ideal weight," she explains.

The idea behind this formula is that 3,500 calories equal one pound, meaning if you cut 500 calories each day for seven days, you'll create a 3,500 calorie deficit and, in turn, lose one pound. "There are all kinds of problems with that," says Sass. "If you take someone below the number of calories needed to get to their healthy weight or their goal weight, they may slow down their metabolism, lose muscle tissue or lean tissue, and have other side effects, like intense cravings or hunger, irritability, mood swings."

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Basing Intake On Your Goal Weight

So how can you determine how many calories you actually need to lose weight without hurting your health? Sass has a hack: Instead of entering your current weight and your goal weight into the app or formula, enter your goal weight in the box that asks for your current weight, and check "maintain current weight" as your goal instead of "lose one pound per week." For example, if you weigh 150 pounds but you want to weigh 130, enter your current weight as 130, and your goal as "maintain current weight."

"That will give you the number of calories needed to get to and stay at 130," she says, "and you'll never undercut your needs or create all of those other side effects."

We tried this approach on MyFitnessPal, first entering a 150-pound current weight and a 130-pound goal weight for a 35-year-old, lightly active woman who exercises four times a week for 60 minutes per session. We marked her goal as "lose 1 pound per week." The app then suggested she eat 1,400 calories per day to reach her goal. Next, we entered the same information, but we said the woman's current weight was 130 pounds and her goal was to "maintain current weight." Her daily calorie allowance came out to 1,780. That's a huge difference.

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Sure, this approach will have you losing weight a little slower than if you were cutting 500 calories per day, but it's unlikely you'll mess up your metabolism, burn muscle, or experience mood changes like irritability. Plus, cutting 500 calories per day isn't sustainable for most people. You'll likely get so hungry or fatigued at some point, that you'll have to increase your calorie intake, which could make you gain the weight right back.

Tracking Calories Is Not for Everyone

Though consuming the number of calories needed to maintain your goal weight is Sass's preferred method when it comes to tracking your intake, she's adamant that counting calories aren't for everyone. "You have to know your personality," she says. "Some people are very data-driven, and they like using numbers and trackers, and they can simply look at that as data. For people who have a more emotional relationship with their bodies and numbers and feel anxiety around counting, it can actually be overwhelming."

Never force yourself to track calories if it stresses you out. Sass says it could end up being counterproductive and drive you to overeat out of frustration or totally give up on your goal. When it becomes all-consuming, it can even trigger a surge in levels of the stress hormone cortisol, which has been shown to increase belly fat, she adds.

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Other Ways to Reduce Calorie Intake

Luckily, if tracking your food intake isn't your thing, there are plenty of other ways to reduce your calorie intake, such as focusing on portion size instead of calories. For example, increasing your portions of non-starchy veggies, like spinach, broccoli, and mushrooms while decreasing your portions of starchy, simple carb foods (think white bread or pasta), will automatically reduce your calorie intake, Sass says.

Some people might also want to try using a tracker just at the beginning to get a feel for what it would be like to eat a healthy number of calories for their goal weight. Sass says she's had patients who didn't think they were overeating, but in reality, they were 400 or 500 calories over where they needed to be.

One more thing to remember: Not all calories are created equal. If you're hitting your daily calorie goal but you're eating fast food all day every day, you might lose some weight, but you won't feel good doing it. If you want to lose weight, whole foods are the way to go.

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