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 is: 10 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.