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How to Run on a Calorie Deficit

With the winter coming to a close soon enough, many people are possibly in the midst of their base building phase and approaching more specific work to prepare for racing.

For many, race weight is likely on their mind.

If you’re looking to lose weight for health reasons, this article may not be for you. If you want to lose weight to run faster, read on!

Why a Race Weight?

If you’re looking to improve your personal records, losing some excess weight can be worth a lot.

Specifically, for each pound lost you could simply increase your pace by 1-3 seconds per mile depending on your starting weight.

To put this into a real-life example, a 150 pound man dropping to 140 would increase their pace by about 10 seconds per mile. That’s :30 over a 5k and a few minutes for a marathon simply by losing weight.

How weight loss improves your speed is two primary reasons. First is you simply have less mass to carry forward and up. Second is your body will dissipate heat more efficiently and cool you better.

What’s your ideal race weight?

Warning: This is going to be a low number!

It’s also not a number that anyone, even the elites, will weigh year round. They may only weigh this for the racing season and then will gain back some in the off-season. It also will depend on your goal races and muscle mass. Shorter distance runners tend to do better with more muscle and weight.

Running Shoe Guru’s writer Peyton Hoyal details what your ideal race weight is, quite well. Peyton suggests to take your height in inches, double it, then based on your frame:

  • Small Frame– Double the inches, then subtract 5-10lbs to establish an optimum running weight for health and performance.
  • Medium Frame– The formula works! Keep it the same.
  • Large Frame– Double the inches, then add 5-10lbs.

For a 67 inch tall person with a medium frame, that come to 134 pounds at race weight.

  • Females could subtract 0-10 pounds from this number as they typically weigh less.
  • Males could add 0-10 pounds to this number, as they typically weigh more.

How to reach Race Weight?!?

There is a bit of a method to running in a caloric deficit, or bringing in through diet less calories than you are using up through activity.

Even some Kenyans will spend at least the month or so before a competition in a caloric deficit, in an attempt to drop a bit of weight before the goal race.

The balance must be found in eating enough food to both lose a bit of weight slowly over time but still fuel your training so you can continue running at your high level. There are many things can can be taken into consideration for this to be done:

High Quality Food

While eating less food, focusing on nutrients is important.

Foods that are more nutrient dense basically include everything but grains and food with added sugar/fat. An issue with calorie restriction is it also restricts nutrients such as essential fat, protein, vitamin, and minerals. High quality food also tends to be rather low calorie, so you can eat more volume of food for fewer calories.

Pre-Workout Fuel

When on a calorie deficit, it’s important to fuel the exercise properly.

Try not to go into long or hard workouts without some sort of pre or intra run fueling.

The purpose here is to both fuel your body so you can perform at your max during these quality sessions, but also to prevent your body’s glycogen from getting too low during these runs. Fasted easy morning workouts are ok, however for harder sessions being in a caloric deficit may hinder your training ability.

Post Workout Food Timing

Research has shown that for recovery and most people, total daily calories is much more important than eating within that 30 minute post workout window when your body is sucking up nutrients like a dry sponge absorbs water. However, if you’re in a calorie deficit or doing another longer workout within 6-8 hours of your previous one, food timing becomes much more important.

This importance comes from a number of factors. Your primary fuel while running in fat and glycogen. Fat is a near endless supply, but glycogen needs to be restocked. Immediately after a workout your body is primarily repairing muscle and restoring glycogen better than at any other time during the day. If you eat take some food right after the run, it will go towards these two purposes, setting you up for your next workouts. Not letting your glycogen stores get too low is key, as if they get low your body will not be able to train at its fullest.

Calorie Reload Day (or weekend, or week)

This serves two purposes.

First, it gives you a higher calorie day to bump up your weekly food intake. No need to go crazy here, just don’t be in a deficit.

Second, it gives you a chance to eat some higher calorie food, a cheat meal. I suggest your cheat meal be your next full meal after your long run, as much of the calories taken in will go to glycogen replenishment (keeping it off your butt, and fueling future runs!)

You can simply do calorie reloading during periods of recover, be that easy days where you do not run as much or full weeks that you run at a lower than typical volume.

How much of a deficit?

Really, as little as possible of a deficit, this could change based on how far out you are from the goal race.

3,600 calories lost is a pound. 400-600 calories daily is a good range. Any less and your weight loss will be nil. Any more and you’re risking sacrificing your quality workouts.


There are a couple tools that make tracking calories easier.

First, is apps like LoseIt! that easily record calories intake and burned. You can scan barcodes and it will even bring up the food!

Second are measure devices. Measuring makes tracking easier! 1c rice, .5c chickpeas, etc. You don’t realize how small a tablespoon is until you can only eat 1 tablespoon of peanut butter.

There are also a couple more methods of weight loss that can be used while training, that may not necessarily require much of a calorie deficit.

Intermittent Fasting

This is, simply put, waiting longer to eat. There are different methods, but many will fast overnight for 12 hours, some longer, some shorter. Fasting does not necessarily mean you eat less total daily calories, only that you may eat less in the morning and then larger lunches and dinners.

Doing easy runs on an overnight fast may increase the fat burning during the workout, which could make you more economic. (one of the theories for why women bonk less than men is because women are better fat burners). If you go into a workout fasted the fuel for that run is coming from body fat and stored glycogen, the next meal you eat will then go towards first restocking those glycogen stores. Doing harder workouts fasted may make the run more of a stress to the body and could then cause more adaptation and fitness gains.

There are also numerous other potential benefits as well.

Standing Desk

This is another “hack” that you can do to burn an extra few calories, if you wish. Calculations suggest that 4 hours of standing vs sitting burns an extra 100-150 calories. Not a lot at once, but over time it adds up!

The Post-Workout Window of Opportunity

Commonly you hear of the PWO Window of Opportunity as a time to eat within 30 minutes after training since your body is absorbing nutrients like a dry sponge absorbs water.

It’s true getting a carb beverage in right after (or even during) a workout does help maximize your glycogen stores. However, if you’re not doing another hard or long run within about 8-10 hours of the last workout total daily calories and nutrients matter much more than getting in food within 30-60 minutes after running.

Using this window of opportunity to lose weight by not eating right away can be a easy method of reaching race weight after time. This will help increase your insulin sensitivity, which means your body is better at lowering blood glucose back down to base level. You’ll also probably eat less overall. Note that you should never sacrifice fueling for weight loss after a key workout!