Precision Nutrition’s Weight Loss Calculator: Here’s what it really takes to reach your goals.


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    It’s a question that comes up from new Precision Nutrition Coaching clients all the time:

    “I’ve been tracking my calories in and calories out religiously… but I’m not losing as much weight as I should. Why isn’t this working?!?”

    Yes, conventional wisdom states that reducing your calorie intake (or increasing the amount you burn) by 500 calories a day should lead to about 1 pound of fat loss per week. (Math: 500 calories a day x 7 days = 3500 calories a week = 1 pound.)

    But that conventional wisdom is wrong. As discussed in this article all about the myth of metabolic damage, your metabolism is adaptive. As you eat less, your metabolism slows, throwing off common assumptions about calorie balance.

    This excellent weight loss calculator—based on the NIH Body Weight Planner and adapted from research collected at the National Institute of Diabetes and Digestive and Kidney Diseases—takes into account the adaptive nature of metabolism and gives more accurate information on how hard you’ll have to work (and how long it may take) to reach your goals.

    (Keep reading below the calculator to learn why it’s more advanced than many others.)

    Body Weight Planner

    Starting Information

    Starting Weight in {{weightUnitsRadioGroupLbl}} Height in {{heightUnitsGroup}} % Uncertainty Range

    % Uncertainty Range

    510152025 Initial Resting Metabolic Rate as {{energyUnitsRadioGroupLbl}}


    Calories Kilojoules

    In order to maintain your current weight, you should eat:

    {{maintCalsField | number:0}}


    To reach your goal of {{goalWeight}} {{weightUnitsRadioGroupLbl}} in {{goalTime}} days, you should eat:

    {{goalCalsField | number:0}}


    To maintain your goal of {{goalWeight}} {{weightUnitsRadioGroupLbl}}, you should eat:

    {{goalMaintCalsField | number:0}}


    At the end of {{simulationLengthField}} days, you would weight:



    At the end of {{simulationLengthField}} days, your Body Fat % would be:

    At the end of {{simulationLengthField}} days, your BMI would be:

    Simulation Details

    Warning: Low BMI The goal weight you entered is below a healthy weight for someone of your height and age.
    A healthy weight range for you is between {{weightRangeLow}} and {{weightRangeHigh}} {{weightUnitsRadioGroup | lowercase}}. The lifestyle changes you entered resulted in a low BMI for someone of your height and age.

    Warning: High BMI The goal weight you entered is above a healthy weight for someone of your height and age.
    A healthy weight range for you is between {{weightRangeLow}} and {{weightRangeHigh}} {{weightUnitsRadioGroup | lowercase}}. The lifestyle changes you entered resulted in a high BMI for someone of your height and age.

    Dangerously Low Intake: Please adjust your lifestyle intake Daily intake must be at least 1000 calories/day. Food group targets and nutrient recommendations will not be met below 1000 calories/day.

    Dangerously Low Intake: Please adjust your goal The information you entered results in a {{energyUnitsLblSrt | lowercase}} level that is too low.
    Calorie goals must be at least 1000 calories/day. Food group targets and nutrient recommendations will not be met below 1000 calories/day.
    The last change you made has been reset so that you can enter a different value. Try giving yourself more time to achieve your goal, changing your activity level, or setting a different goal.

    Length of Simulation (days)

    Initial Weight ({{weightUnitsRadioGroupLbl}}):


    Initial % Fat:


    Initial BMI:


    Final Weight ({{weightUnitsRadioGroupLbl}}):


    Final % Fat:


    Final BMI:


    Note: If you have questions about how to use the calculator, check out this video tutorial.

    To understand why this calculator is so helpful, let’s use an example client: Vanessa. She’s 40 years old, 5’ 6” tall, weighs 185 pounds, has a very low level of activity at work, and a moderate level of activity outside of work.

    Based on this information, the calculator has determined that she needs around 2,445 calories per day to maintain her weight.

    Let’s say Vanessa would like to lose 40 pounds in a sustainable way over the course of the next year, without doing much additional exercise.

    The calculator suggests she’ll need to reduce her food intake to around 1,770 calories per day. (That’s 675 calories fewer than required for maintenance.)

    If you do conventional calorie math, these numbers don’t make sense.

    A daily calorie deficit of 675 calories would lead to a deficit of 246,375 calories over a full year. (Math: 675 calorie deficit x 365 days = 246,375 calories.)

    This would, theoretically, lead to a 70-pound weight loss for Vanessa. (Math: 246,375 calorie deficit / 3,500 calories in 1 pound of weight = 70 pounds lost.)

    But the body doesn’t work that way. Instead, Vanessa would lose only about 40 pounds. (Which is still awesome, obviously.)

    Why this very large disparity?

    As mentioned above, your metabolism adjusts as you eat less and lose weight. And conventional math doesn’t take this complex nature of human metabolism into account.

    That’s why it’s important to make sure your expectations about weight loss and body change are in line with how your body actually works.

    This calculator helps with that. It makes easier to set appropriate behavior goals, and gives you a more realistic view of what you potential progress could look like.

    But here’s what it can’t do: Predict all the other factors that affect your ability to lose weight. It doesn’t take into account your unique food preferences, lifestyle, or abilities.

    So while meticulously tracking calories can be a viable approach to weight loss for some, our experience coaching more than 100,000 clients says there are easier, more successful approaches to losing weight and keeping it off.

    That’s why at Precision Nutrition we coach the whole person, addressing all the factors that lead to sustainable and life-changing results.

    From learning to eyeball portion sizes and better gauge hunger, to improving sleep and managing stress, to finding easier ways to make time for exercise, we help every client build the array of skills they need to get in the best shape of their lives… no math required.

    Want to get in the best shape of your life?

    With Precision Nutrition Coaching, every clients works with a personal coach to achieve the lasting results they want.

    We’ll help you lose fat, get strong, and improve your health, no matter what challenges you’re dealing with. And we’ll meet you wherever you are right now: any body type, any fitness level, any goal. You tell us the results you want, and we’ll show you the way, with compassion and expertise.

    Join us and discover what’s really possible when you have the right help: a highly-skilled coach who’ll guide you every step of the way.

    (If you’re a health and fitness professional who wants to learn the Precision Nutrition method—which has been validated in multiple peer-reviewed scientific journals—explore what our Level 1 and Level 2 Certification programs have to offer you.)

    Interested in Precision Nutrition Coaching? Join the presale list; you’ll save up to 54% and secure a spot 24 hours early.

    We’ll be opening up spots in our next Precision Nutrition Coaching on Wednesday, January 13th, 2021.

    If you’re interested in coaching and want to find out more, I’d encourage you to join our presale list below. Being on the list gives you two special advantages.

    • You’ll pay less than everyone else. At Precision Nutrition we like to reward the most interested and motivated people because they always make the best clients. Join the presale list and you’ll save up to 54% off the general public price, which is the lowest price we’ve ever offered.
    • You’re more likely to get a spot. To give clients the personal care and attention they deserve, we only open up the program twice a year. Last time we opened registration, we sold out within minutes. By joining the presale list you’ll get the opportunity to register 24 hours before everyone else, increasing your chances of getting in.

    If you’re ready to change your body, and your life, with help from the world’s best coaches, this is your chance.

    [Note: If your health and fitness are already sorted out, but you’re interested in helping others, check out our Precision Nutrition Level 1 Certification program].


    Click here to view the information sources referenced in this article.



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