If you want to lose body fat, gain muscle or maintain your weight, there's an important health metric you should know about: your basal metabolic rate. Your BMR is the minimum number of calories that your body needs to function at rest. You may think you only need energy to exercise or complete tasks, but your body has a specific energy need just to complete basic functions like breathing and regulating your hormone levels.

Your BMR is not in itself a tool for weight loss, but it can be a helpful starting point for figuring out how to adjust your diet and exercise goals. The problem with a lot of diets and weight loss programs out there is that they are "one size fits all." But every person is different, so taking one meal plan and applying it to multiple people just does not work. Your BMR is calculated based on several different factors that are personal to you, like your age, gender, current weight and activity level.

Keep reading to find out about what BMR is, how to calculate it and how it can help you with your nutrition and exercise goals.

Read more: How Many Calories Should You Burn Each Day to Lose Weight?

BMR calculators use several different factors, like age and gender, to determine your BMR.

Many people use BMR as a starting point to calculate their daily calorie needs and how to best adjust them to reach their goals. In fact, many macro calculators, like the popular IIFYM, incorporate BMR into their calculations for telling you about your calorie intake and macro needs based on your goals.

One common misconception about BMR is that it is the amount of calories your body burns at rest, but that is a different metric -- resting metabolic rate or (RMR). Your BMR is what energy your body needs to perform basic functions, while RMR is the amount of calories that your body burns while at rest. Some people use the measurements interchangeably, but they aren't necessarily the same thing.

There are many different calculators available online that can calculate your estimated BMR. Note that some of them will ask you to enter your body fat percentage, which many people do not know. If you don't, you can make an estimate or use the images provided (like IIFYM does) to guess.

Some of the best BMR calculators:

Once you start learning about your BMR, you will likely also find information on total daily energy expenditure, orTDEE, since BMR is often calculated first to find TDEE.

Your BMR tells you your calorie needs, when you take that number plus how much you burn every day during normal activity and exercise, you get your TDEE. So really, TDEE is the number that you work off of for figuring out how to adjust macros or calories for body composition goals, according to IIFYM.

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Weight loss is tricky, but using calculators that factor in your BMR are helpful for taking a more customized approach for your calories and macronutrient needs. The way that most macros and BMR-based calculators work is by factoring in your TDEE with your goals.

If you want to lose weight, you have to be in a calorie deficit, meaning the calculator will set your daily food intake to equal less calories than what you burn. Sometimes when you take an online quiz to find this number, you will be asked how fast you'd like to lose weight. Then the calorie deficit will be adjusted accordingly. The faster you want results, the more extreme you will have to be with cutting calories. But many experts say that slow and steady is optimal compared to trying to lose a lot of weight quickly.

If you want to maintain your weight instead of lose or gain, then knowing your BMR and TDEE can help you know how many calories you should aim to consume each day to maintain your weight. On the flipside of weight loss is gaining muscle mass. This too requires that you strategically approach your nutrition and add calories into your day (likely in the form of protein and carbs) to make sure you can gain muscle.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.

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Your BMR Is the Key to Losing Weight or Gaining Muscle - CNET