Cutting Calories = Weight Loss, Right?

This post is a reprint with some changes of a prior post.  I’m re-posting this with some changes because there is an epidemic going on. The epidemic is athletes thinking they need to eat 1200 calories/day to lose weight. Athletes are different from Sam and Sally Couch-Sitters. Sam and Sally Couch-Sitters may need only 1200 or 1500 calories/day to lose weight. Athletes need more. Often WAY more. How much more?

You start by determining you estimated Resting Metabolic Rate (RMR). Your RMR is the base number of calories your body needs to live if you stayed in bed all day. Your RMR is your zero point for the number of calories your body needs to live. If your RMR is 1500 calories that means you don’t eat less than 1500 calories. If you eat less than 1500 calories for a period of time (2 – 4 weeks lets say), your RMR will get slower. A slower RMR means it is easier to gain weight. Not what most people want. (The details of calculating your RMR are further down.)

Next, you multiply your RMR by an activity factor. I use an activity factor based on your daily, non-workout activity. If you sit at a desk all day and don’t walk around much, I’ll use 1.3 or 1.35. If you’re walking around a lot, I’ll use 1.4 or 1.5 depending on how much time you spend sitting down. (Again, more details are below.)

Then, you add calories for workouts. Most of us wear gadgets that give us an estimate of how many calories we’ve burned. You can plug in that number to the number of your RMR x activity factor. This is the number of calories you need to maintain your weight. Next, you subtract 500 to 1000 calories for weight loss. However, if this number is less than your RMR, your base number of calories is your RMR (remember, we don’t want that to slow down – right?).  I don’t like athletes to have greater than a 1000 calorie deficit per day. To me that’s just too many calories to not have for your body’s fuel. You’ll be hungry, sluggish, and won’t have good workouts.

Remember, if you’re an athlete, you need to fuel your body with food. I have clients who have an RMR of 1500 calories, and need 1800 calories without workouts, then need  another 1200 for workouts. This means they need 3000 calories a day. Then, they eat 1200 calories a day and don’t lose weight. Their bodies are mad and are holding on to everything they are eating because it is trying to have enough calories to live, much less do the workouts. When they start eating more, they start losing weight, putting on muscle, and getting happy with how they look in the mirror.

If this sounds familiar (or even if you just want to know), take a few minutes and follow the steps below to determine your calorie needs. Please, help me stop the epidemic! If you’re an athlete, feed your body to perform (and make the body composition changes you want to happen).

How to Determine Your Calorie Needs

Determining how many calories you need can be tricky. If you google “how many calories do I need” you get hundreds of results with all sorts of different calculators. How do you know which is right for you? The thing to remember is that the calculations are a best guess. If you really want to nail down your calorie needs, then you can have your Resting Metabolic Rate (RMR) measured. However, if you can not have it measured, the formulas are a good place to start.

When I’m calculating calorie needs, I prefer the Mifflin-St. Jeor equation. This equation has been found to be most accurate in a variety of people.  The formula is below. The weight is in kg and height in cm. To convert your weight to kg, divide your weight in pounds by 2.2. To convert your height to cm, multiply your height in inches by 2.54. Here is the Mifflin-St. Jeor formula:

Men: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5
Women: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161

This gives you an estimate of your RMR – which is, basically, how many calories you would need if you hung out on the couch all day. Since that is not the case for most of us, I multiply the RMR by an activity factor. The way I do it for my clients is to choose an activity factor for their day that does not include their workouts. Here are the activity factors:

  • Sedentary (little or no exercise) = 1.2
  • Llightly active (light exercise/sports 1-3 days/week) = 1.375
  • Moderately active (moderate exercise/sports 3-5 days/week) = 1.550
  • Very active (hard exercise/sports 6-7 days a week) = 1.725
  • Extra active (very hard exercise/sports and physical job) = 1.900

Finally, I add in the calories for workouts. Most athletes have a Garmin or heart rate monitor that gives them calories expended in a workout.

Here’s an example. Sandy is a marathoner who has a desk job. When she is home and not working out, she is playing with her two small children and doing house work, washing clothes, etc. She doesn’t sit much when she is at home. She is 32 years old, 5’5″ tall and weighs 140 pounds. She does not want to change her weight or body composition.

  • 65 inches  2.54 = 163.15 inches
  • 140/2.2 = 63.6 kg

The Mifflin-St. Jeor equeation for women is10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161

Sandy’s RMR would be (10 x 63.6) + (6.25 x 163.15) – (5 x 32) – 161 = 1337 calories per day. Given her work and at home (non-workout activities) I wouldmultiply her RMR by 1.35 (1337 x 1.35 = 1805 calories per day). Her workouts range from short runs when she burns 400 calories to long runs when she burns 1200 calories. This means that:

  • On Sandy’s off day, she should eat about 1800 calories.
  • On her short workout days, she should eat about 2200 calories.
  • On her long workout days, she should eat about 3000 calories.

For most people, this gets a little overwhelming. To make it easier, we look at a seven day average. It is OK to move some calories (200 – 500) from your long workout day to the day before or after to pre-fuel and get you over being extrahungry on your day off.

I hope this helps you determine how many calories you need. If you have questions, let me know.


  1. Bob Matthis says:

    But, if Sandy wants to lose 1 pound a week she should eat 1800-500=1300 calories a day. Plus whatever she burns in her workouts. Right? or no?

  2. Bob Matthis says:

    Ok. I commented too fast. You clearly said she should not eat less than her RMR which is 1800. And, she should add in her workout calories. I don’t get how she loses weight this way.

  3. Hi Penny,

    Found my way here from one of your posts on EN…so interesting! I’ve been using MyFitnessPal to track intake/goals and it gave me a 1500-ish target to lose 1.5 lbs a week. The formula above gives me a RMR of 2096!! I have lost about 13 lbs starting at the November OS just tracking intake and burn, but have plateau’d since upping my training volume. FWIW my profile: 5’11, 188lbs, desk job (so I used 1.2 for activity factor), 48 years old, recent body fat measurement at 23.2%.

    Your comments above make sense and I am going to try fueling my day per your guidelines, especially since my IM build starts now and I would like to drop another 8-10 before Lake Placid. Thanks for posting the explanation

    • Hi Rich,

      I’d up your activity factor. The normal is 1.25 if all you do is sit on the couch all day. For a desk job, I usually use 1.3 or 1.35 depending on how much you get up and move around.

  4. Bob Matthis says:

    Penny, thanks! I also have been using Myfitnesspal. It had me on 1200 calories/day (to lose 2 pounds/week). Then you add to that whatever calories you burn and you eat those additional calories,too. I’ve lost weight slooooowly. If I reset the app to lose a pound a week it gives me a daily calorie goal of 1600. This is basically my RMR with no factor for activity. (59 years, male, 190 pounds, 5’10”). I try to exercise 6 days a week. I don’t always manage it.
    I have reset it and I’ll try it with the higher daily calories.
    Thanks again!

  5. sakinagroth says:

    I just don’t understand how this works! I’ve been eating my RMR + anywhere from 100-600 cals a day for over a year. I’ve been monitoring what I eat, what I burn, everything. I run or strength train 4-5 days a week, but never have a deficit of more than 1000 calories. I very slowly lost about 5 lbs, then somehow put them ALL back on in one week on my honeymoon (and I did the math, there is no way I ate enough to warrant that), and now they just won’t come back off. What the heck do I need to do? Has my body adapted to the exercise? When I talk to nutritionists/trainers at my gym, half tell me I need to eat more, and the other half tell me I need to eat less (stick to 1200 calories). Then of course there’s all the controversy about carbs or no carbs. BTW I had my metabolism tested and my RMR is 1122.

    • Oh, I feel your pain! Sometimes I feel like I can look at food and gain weight.

      Have you had a physical lately and your thyroid checked?

      Carbs vs. no carbs really is starch vs. no starch. It depends on the person and what’s going on with them as to if this is an OK approach or not. I do find that for a lot of my clients limiting starches (anything grain-based, potatoes, sweet potatoes, corn and peas) does help bring weight down.

      Let me know if this helps or if you have more questions!

  6. Obviously athletes burn more fats / calories daily compared to couch persons so it’s really not right to eat as less as couch people do in their diet plan, I think if athletes do, they’ll end up fainting. I mean, their agenda needs energy which they wont get if they wont eat enough.

    • Good point Harry! They may or may not faint, but they won’t perform as well during their workouts or during the day. A lot of times, they’re very sleepy.

      • Hi Penny, I’m 6’1″ 208 lbs and 35 years of age. I’ve been consuming around 2200 – 2500 calories and have very slowly lost 13 lbs in the course of 2 years. My weight lifting is very strenous. Lately I’ve been very sleepy during the day. Then I came across your site and performed the calculations which shows I must consume about 3200 calories. The fact that you mentioned how someone can feel lethargic or sleepy during the day was like a light bulb just went on. My workouts are awesome due to consuming 2 medjool dates a bananana, whey protein, Dannon Greek yogurt and creatine 30 minutes before training, which boosts my energy big time. However, from morning until that time I’m just sleepy and have been wondering why, so I guess I need to consume 3200 calories to start burning fat the right way, correct?

        • Penny Wilson says:

          Hi Mike: Two main things come into play when you want to burn fat. First, are you eating enough calories. Second, what zone are you working out in. It does sound like you need to eat more. You can always increase it and see what happens. I actually see people start leaning out when they start eating more. I’d try that first and see what happens. I’d bring it up to 2800, then 3200 and see where your personal “sweet spot” is. Keep me posted!

  7. Katherine Parks says:

    Hi Penny,

    My husband keeps telling me I don’t eat enough. My RMR is 1377 and I generally eat around 1200 calories. I have come to a dead halt as far as losing any more weight and I actually started to gain weight despite the fact I work out 6 days a week close to 90 minutes (40 to 50 cardio, rest HIIT or Circuit training with weights (Insanity or Spartacus workout). I am 37 and 5’1. I also have two small kids and I do play with them quite often. I do sit during the day for about 4 hours at most. The rest I am up and moving around doing housework or chasing kids. I was down to 130 and I have put back on around 8 pounds. I know it’s not a lot but according to the “guidelines” I am overweight due to my height. I do have a lot of muscle too. The doctor did check my thyroid and I am ok in that area. According to your calculations I should eat the same as Sandy basically.

    Is it possible that I am not eating enough? Let me add that I do like sweets but I limit myself to small amounts on a daily basis so it could be a small piece of dark chocolate or a cookie. I am very frustrated at this point and would appreciate a few pointers!

    • Hi Katherine,

      Yes, it sounds like you are not eating enough. If your RMR is 1377 and you’re eating 1200 calories you’re asking your body to exist and do all the other things you want on less than it needs to live – 1377 calories. What happens when you eat under your RMR is that your body starts slowing all the metabolic processes down to conserve energy, maintaining or putting on fat because your body thinks it is starving, and starts to get rid of muscle because muscle requires more calories to maintain than fat. Not losing weight and putting on weight would make sense in this scenario.

      Here’s what I’d recommend: start bringing up your calories 100 – 200 calories every three to four days until you reach the number of calories your body needs.

      Does that help? Let me know if you have other questions!

  8. Hey I am so thrilled I found your weblog, I really
    found you by mistake, while I was searching on Aol for something else, Regardless
    I am here now and would just like to say cheers for a marvelous post and a all round
    entertaining blog (I also love the theme/design), I don’t have time to read through it all at the minute but I have bookmarked it
    and also included your RSS feeds, so when I have time I will be back to
    read much more, Please do keep up the great work.

  9. Hey! I know this is kinda off topic but I was wondering if you knew where I could get a
    captcha plugin for my comment form? I’m using the same blog platform as yours
    and I’m having problems finding one? Thanks a lot!

  10. I have a question, I an seeing a dietitian, I had a RMR done and was told it’s at 1600. I was advised to eat no more than 1100 calories a day. I was doing the optifast program but after 8 days and losing 4 1/2 lbs I realized I couldn’t afford to stay on the program. I drank 5 shakes a day plus 64oz of water. She now had me drinking 2 shakes a day and taking in no more than 700 calories the shakes are 160 each. I am 53 5ft 6in and 46 lbs overweight, I just finished going through the change of life. I am so confused about the calories I am suppose to take in to lose weight. My activities vary from day to day depending on rest and energy. Please give me your thoughts on this. Thank you.

    • Penny Wilson says:

      Hi Susan and thanks for your question. Honestly, I’m not a fan of very low calorie diets like OptiFast for a number of reasons. If you’ve gone through the change of life, I’d first check to be sure your hormone levels are optimal with your doctor. Once you are sure your hormones are fine, then I’d start tinkering with the macronutrients in your diet. I’ve had success taking people up to 40-50% fat with less carbs and a good amount of protein. This provides your body with fat to use as an energy source and to produce more of enzymes needed to burn fat as fuel – both the fat you’re eating and have stored. If you want to talk further, you can send me an email using the “Contact” button on the website. Have a great day!

  11. Hi Your blog is great and very informative. I am a Female 5 Feet 4 inch tall, 84 KGs, 29 Years old. My RMR is 1555*1.55(activity 3 to 5 times a week). But 2400 calories per day looks like too much for me 🙁 How many grams of protein do I need to take a day considering I am vegetarian. Also my fat % is 42 and it isnt coming down. Currently taking 1500 to 1600 calorie diet and around 60 grams average protein per day.

    • Penny Wilson says:

      Hi Elena,

      I’m not really comfortable giving nutrition advice through my blog. Let me know if you’d like to setup a quick phone call to talk about what’s going on.

  12. So I have calculated my body needs 2634 calories (I have 60 kilos to lose). If I cut my calorie intake to 1800 per day, will this help lose weight or should I cut to 1500?

  13. Hi penny
    I am 44 years old and 5 ft 3″ and weigh about 251 pounds . My RMR is 1512 . I want to loose weight . Oh and I have sedentary life style. To loose weight with diabetes type 2 difficult please can you suggest how many calories per day for weight loss of 2-3 pounds per week. Thanks in advance .

    • Penny Wilson says:

      Hi! Honestly, I’d recommend you start by increasing how much you move. Start walking and increasing the number of steps you get daily. It is hard for me to answer this question in a commend. Really, we’d need to talk so I’m sure I understand all that is going on with you.

  14. My husband is urgently trying to lose weight for an upcoming surgery. He’s on Optifast which has been very effective. However, he’s not following it exactly and has gone down to sometimes 500 calories per day or less. He’s also working out 6 days a week (1 hour fast walking on the treadmill). Today, he passed out when he got out of bed. He was 130kg and today he us 121kg. He stumbled and I tried to catch his fall, but failed to, and both of us had quite a bad fall, and were just inches away from hitting our heads on the edge of the bedside table. I have hurt my right shoulder badly after falling under his weight and he has a sore back from having fallen on the edge of the arm of a chair too. So I hope anyone who is looking to lose weight will think seriously about calculating the right amount of calories needed to function properly, particularly with workouts thrown in. Fainting isn’t the most dangerous thing, it’s having a bad fall (and bringing someone else down if you are overweight). The journey is a long one for weight loss, and sometimes it’s frustrating when the scales don’t budge. But we just listen very closely to what our bodies tell us. Every one of us is different and our physical requirements are very different regardless of similar heights etc.

Speak Your Mind