Why the 90/10 Diet Plan is the Most Realistic for Runners

This guest post was written by Heather Caplan

There’s no rule saying you have to wait until the new year to step back and reevaluate whether or not the way you eat is fueling your running goals.

Now is as good a time as any!

If you feel ready to try something new, there are a variety of options to test out.

But proceed with caution and patience.

With or without the guidance of a nutrition professional, it’s common practice to go all in with dietary changes, to try to eat according to the rules 100% of the time without any exceptions or even a single cheat meal.

Even with the right idea, these 24-7 100%-on diets rarely, if ever, yield the desired weight loss result we hope for, especially if you are running to lose weight.

Today we are going to look at one runner diet that is realistic, and show you why the 90 10 diet plan might actually be the way to go for runners, especially as it allows daily cheats, and no foods that are completely banned.

We all know what happens when we are told we can’t have something…we want it more!

Learn how to use the 90 10 nutrition guidelines, and make this the first time where you reach your goal weight without sacrificing your running goals, and still get to enjoy your favorite foods.

Why the 90/10 Diet Plan is the Most Realistic for Runners


It’s worth noting that this lack of follow-through isn’t unique to diets altogether.

It’s a common consequence of doing too much too soon.

Runners know that the too much too soon approach to training is risk factor for injury, bringing any endurance or strength progress or goals to a halt.

Runners often follow the increase by 10% rule, easing into distance and speed slowly, not 100% right away.

Yet when it comes to drastically changing what, when, and how much we eat, it’s more common to do do too much too soon.

Instead of going all in with dietary changes, eating by dietary rules 100% of the time, I suggest using the 90/10 rule.

What does it mean to eat with a 90 10 diet?

Embracing a 90/10 mindset with food means you don’t put pressure on yourself to perfectly follow any given diet rules.

You allow yourself some flexibility and are okay with the occasional “junk” food (we all know what’s junk and what’s not).

But you do eat nourishing foods—fruits, vegetables, animal and/or plant-based proteins, high fiber grains, fish, fats, etc.—most, or about 90%, of the time.

The remaining 10% gives you room to enjoy a drink, dessert, mid-afternoon treat, or whatever your vice of choice may be.

Here’s the deal:

The 90/10 rule means relaxing the pressure to eat well all day every day, 100% of the time.


When you look at most definitions of “healthy”, trying to eat healthy 100% of the time is not a sustainable mindset.

Being 100% clean often leads to feelings of deprivation, and sometimes desperation, which eventually backfires, meaning you don’t lose weight, even during marathon training, have elevated stress levels, suffer from mood swings, and many other negative side effects.

Runners think of food as fuel for training, but it should also be something you enjoy.

This is important:

Notice we are calling this a 90/10 (or 80/20!) mindset, not a calculation.

In order to have success with this diet, you don’t have to start adding up everything you eat and calculating which percentage (90 or 10, 80 or 20) any given meal or snack contributes to.

Think of this as a general food philosophy that will help you have a more sustainable relationship with food and fueling for your training.

Try following the five steps below to relax the strict diet mentality, but still make a few changes to your daily food habits, and to embrace this 90/10 mindset.

Avoid the urge to cleanse your diet

One of the popular diet approaches right now is cleansing.

Some people use this as a way to jump-start major dietary changes, some use it to “feel better” after a period of indulging (e.g. holidays,, travel, etc.), and some just to lose weight quickly.

There are plenty of products and tips online for cleansing, but few of them are anything less than an extreme way to restrict food intake and/or eliminate whole food groups at a time.

This may lead to a restrictive diet mentality and a tendency to continue avoiding food groups, which eventually leads to nutrient deficiencies with extreme calorie deficits.

Both energy and nutrient deficiencies are detrimental to a runner in training, especially if you are following a marathon training schedule, or even habitual runners who are looking to reach their optimal mileage.

Without a food allergy or medical advice to avoid a certain food or food group, there’s no reason to go the elimination, or cleansing, route.

What’s the bottom line?

Avoid the urge to start any dietary changes with any sort of extreme cleanse, or to use this tactic as a reset button.

Instead, start with step number two.

Identify small changes, and start with one at a time

Change your nutrition at the same pace you would increase your running: slow and easy, just a little bit at a time.

Start small and build on those changes, bringing you to the 90/10 mindset gradually.


Either keep a food log for a few days or simply think back to what you’ve had to eat for the past twenty-four hours.

Look it over and think about each meal and snack, why you ate what you did, whether or not you were actually hungry at the time, or whether you were just bored (which we are all guilty of eating in this way sometimes).


Identify what habits, or meals specifically, you want to work on.

These are often obvious; you may find yourself observing things with the “I should have” lens.

For example:

I should have had more vegetables yesterday.

I should have drank more water in the afternoon.

I should have had a snack so that I wasn’t famished before dinner.

In those three observations you have three nutrition goals to start with!


Choose one goal to work on at a time, for at least three to five days.

Take the “more vegetables” as an example.

First, break that down into a more specific (S.M.A.R.T.) goal, such as, “have a small side salad with lunch everyday” or “snack on sliced peppers and hummus in the afternoon.” (1)

Try to do that every day until it starts to feel normal.

It may take a few days; it may take one or two weeks.

This is important:

Don’t put expectations on every other meal or snack, just that one. This helps you ease into the 90/10 mindset.

Take it slow and easy, just like a long run.

What’s the bottom line?

Allow yourself time to adjust to this change in your diet, just like you give yourself weeks to gain fitness.

Don’t try to change everything in your diet at once

This goes back to tip number one: even if you do plan to make a lot of nutrition changes, don’t try to change everything.

Avoid the urge to change everything about your current routine.

It’s not only hard to change your habits, but also hard to break them.

Think about what fits into your 10% bucket, and be OK with those things.

You may need to repeat the process outlined in tip number two (food log for a day, review, identify small changes to make, start with one at a time) a few times, and it may help to enlist the services of a nutrition professional.

But it’s OK to keep a few vices that you enjoy as part of your daily diet.

Fill up that daily 90% bucket with balanced meals (carbohydrates, proteins, and fats) within the two optimal windows for recovery following a run, include three to five servings of fruits and vegetables, high-fiber foods (grains, vegetables, nuts), and meals/snacks portioned to your needs.

Keep your 10% open for nights out with friends, celebratory desserts or meals, indulgent weekend brunches.

What’s the bottom line?

The goal in adopting a 90/10 mindset is to practice moderation and avoid extremes. You do not want to change everything about the way you eat.

Trying to go back to square one with food will be overwhelming, and is probably unnecessary.

Eat when you’re (physically) hungry

Diet or not, one frequently overlooked aspect of nutrition is physical hunger.

We eat for a variety of reasons—snacks or meals may be triggered by stress, time of day, boredom, or some other emotion—but are not always physically hungry.

Start to pause before you eat a meal or snack to assess your physical hunger level.

You could try using the hunger scale (2), or simply ask yourself,

“Do I feel hungry?”

If you are not sure if you are really hungry, here are some things to consider:

Do you have an empty feeling in your stomach?

Low energy levels?

Slight trouble focusing?

Intense concentration on food or what to eat?

If you answered yes to these, then have a meal or snack.

If you don’t feel the physical signs of hunger above, try to identify the emotion you do feel.

Is it stress, boredom, anxiety, fear, you are feeling?

Take a moment to think about what may be a better way to cope with that emotion, instead of food.

If you are struggling with your caloric balance for running, there are other indicators you can use.

On the flip side, it can be just as common for people to ignore physical hunger signs (for a variety of reasons, one of which may be a weight loss goal).

In this case, becoming famished, moody, maybe even slightly dizzy or unable to concentrate, is a form of stress to the body, and will cause your body to cling on to any fuel you do put in, as it will be in fear of starvation.

Try to eat before reaching this level of intense of hunger.

You could do this by having snacks on-hand or planning meals and snacks ahead of time if you know you usually get hungry two to three hours after a meal.

What’s the bottom line?

One key to eating enough to fuel your training is being aware of physical hunger, and honoring it with nutritious foods.

In a 90/10 mindset you teach yourself to eat when you’re hungry, instead of trying to stick to certain calorie, meal time, or diet rule.

Diet plan feedback

After a training run or workout you may log it Strava, or send your coach a note, with how it felt.

Try doing the same with your nutrition.

You could use a pen-and-paper or online journal to check in regularly with how your nutrition changes feel to you.

This does not have to be a daily food log, just a regular nutrition or health journal.

Here are a few examples of things you could track:

Your energy levels, mood, sleep patterns, maybe some meals and recipes you love, and how you feel emotionally.

Other things to consider:

Are you running well?

Do you have energy throughout the day?

Are you sleeping well?

Are you experiencing any indigestion?

Do you have regular bowel movements?

These things are notable because a dramatic change in mood, trouble with sleep, low energy on the run or throughout the day, and daily bowel movements could be indicators that you are on the verge of overtraining.

If you reach this point, you can eat yourself out of overtraining, but it will take a long time to bounce back.

What’s the bottom line?

When you’re eating enough to fuel your training and enjoy a variety of foods within the various food groups, you should be sleeping well, have stable energy levels throughout the day, and sleep soundly.

(Of note: many stressors may affect sleep, food is only one of them!)

The goal with this type of feedback journal is to stay balanced, to make sure you’re fueling enough for your training and sticking to the 90/10 mindset instead of resorting to extremes.

Why Should Runners Try the 90/10 (or even an 80/20) Diet?

Many commercial diets present an all-or-nothing strategy, which often leads to extreme cravings, fluctuations in weight (both down and back up), and a low chance of successfully improving health and fitness.

Rather than trying to go all in, all the time, take a step back and try the 90/10, or 80/20, mindset with your nutrition.

Again, this is not to suggest you start calculating the percent of time you spend eating the “right” things, or “junk” foods.

The approach I endorse is that in which you ease up a bit on the food rules of right vs. wrong, healthy vs. unhealthy, clean vs dirty, or whatever categorical system of choice.

Fill up your 90% bucket with foods that nourish you and fuel your training, and use the 10& bucket to stay flexible and relaxed with your diet mentality.

The 10% of your favorite foods gives your brain a rest period and brings joy to your eating, which is equally as important for mental health, as Lanni Marchant, Canadian Record Holder discovered when she restricted her food intake in her 20s.

Without rest, we have no gains.

Without a break from drastic changes, we have no chance to check in with ourselves.

Approach changes to your diet as you would a new training schedule; start with small changes first, and build on them to get to your goal.

Once you hit your stride with foods that give you energy, help you recover, and adequately fuel your health and training, take notice of what works for you.

Finally, don’t take your diet too seriously.

Keep in mind that taking a training cycle too seriously, 100% of the time—no matter what level you run or race at—often leads to mental and physical burnout; nutrition is no different.

Experiment with foods to see what works best with you, and start with small changes.

Don’t take your diet too seriously, leave some room for the treats and experiences you enjoy most.

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Heather Caplan is a registered dietitian and marathon runner in the DC area.She coaches runners for Team Amazing Day, and can be found through her website, heathercaplan.com, for all coaching and nutrition inquiries.

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University of Virginia, Human Resources: S.M.A.R.T. Goal Setting
MIT Medical: The Hunger Scale

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