Why Flexible Dieting Is the Ultimate Method for Improving Health and Fitness

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It's time to talk about flexible dieting. Have you heard of it? If not, here's the gist of it:

Flexible dieting is the least restrictive way of dieting.

It allows people who follow it the most amount of freedom to choose what foods they eat (autonomy) so they can truly make a lifestyle change, rather than following another "only eat these things, never eat those things" type of diet that nobody but people with disordered eating are willing to follow for more than a few months. 

It's the basic premise behind one of the most effective weight loss programs in the world (you've probably heard of it): Weight Watchers.

I see their Freestyle program advertisements while catching up on my favorite shows on Hulu (Modern Family, Broad City, Superstore, The Mick, and Shameless, in case you were looking for hilarious shows).

How can this be possible? Why are most folks absolutely killing themselves trying to gut it out with hyper-rigid diets when Oprah is having a taco party in her kitchen and enjoying a great time with her friends? 

Is it fantasy? Just another fitness industry gimmick to separate consumers from their cash?

Let's take a closer look at what it actually is, and why it works so well...

First off, the science behind our motivation for healthy choices (self determination theory) tells us that we're more likely to give more priority to, be consistent with, and pour more effort into choices that we make on our own (opposed to choices that are imposed upon us, like by a particular diet filled with a lot of don'ts and shouldnt's

The same is true of exercise, by the way.

If we allow ourselves the freedom to make our own informed choices, based on empirical data rather than speculation and unfounded demonization of certain foods/food groups, then we afford ourselves the gift of lifelong (not on-again, off-again) health and fitness.

But can you really eat anything you want, with no consequences?

No, of course not. Even too much "healthy" food will make us fatter. However, that's the straw-man that opponent's of flexible dieting prop up and attack in order to justify their ideology.

It stems from the early days of flexible dieting, when a thing called "IIFYM" (or "If It Fits Your Macros") came onto the scene and 17 year old fitness guru's (that's an oxymoron, in case my sarcasm isn't translating digitally) were getting ripped to shreds eating pop tarts and ice cream and telling everyone else that they could, too. 

Obviously, there was a huge backlash from the opposite end of the health-and-fitness spectrum (the uber-healthy juggernauts that won't "poison their temples" with such things) that still echoes to this day. 

Fortunately (or unfortunately for the pop tart fiends), that isn't what flexible dieting actually is. No serious proponent of a flexible lifestyle is out on the streets with a megaphone telling people to eat more processed foods for better health. 

Why It Works

What flexible dieting does say, however, is very similar to any healthy diet: eat a variety of mostly whole, unprocessed foods. 

And when life happens and you find yourself up s***t creek with an unfortunate lack of paddles, you don't have to say "f**k it" and eat ALL OF THE PIZZA. You can just have a piece, feel no guilt or shame about it, and get right back on track as soon as possible. 

From a psychological perspective, flexible dieting looks to be the obvious choice. But what does the research say about its effects on body composition? 

  • Can you eat carbs and still lose weight?

  • Do you have to reconfigure your entire life just to follow some bastardized version of the ketogenic diet because that's what everyone else is doing these days?

  • Do you have to eat all of your food in an 8-hour window in order to see results, or do you have to eat small, frequent meals throughout the day?

The scientific consensus is that most diets work, when they adhere to a few key points:

  1. Calories must be accounted for (in some way). This doesn't necessarily mean busting out MyFitnessPal at every meal, but creating a caloric deficit through diet and exercise is the prime directive of any successful weight loss endeavor. The opposite is true for weight gain (creating a consistent caloric surplus). This isn't a theory--it's established science.

  2. Protein is sufficient to preserve lean body mass while in a sustained caloric deficit (anywhere from 1.4 grams of protein per kilogram of bodyweight, up to 3.1 grams of protein per kilogram of fat free mass).

So if calories are controlled and protein is equilibrated between diets--it doesn't seem to matter much if the rest of your calories come from mostly carbohydrates, mostly fats, or any combination that still allows for a caloric deficit (for weight loss) or a caloric surplus (for weight gain). 

And it doesn't seem to matter much whether you do intermittent fasting or eat more frequently throughout the day. 

When it comes to changes in body composition, energy balance reigns supreme. 

Optimal vs. Practical

There's a lot of talk these days about "optimization" and doing things in the "best way possible."

But let's be real...the vast majority of us aren't in a position to be optimizing. 

We need to be practical, first.

We need to be consistent.

We need to be able to be flexible and adapt to life's ever-changing demands. 

THEN, if we still want to, we can get fancy and "optimize." Though I'd argue that something that if something isn't practical, it isn't optimal, either. 

This doesn't mean that there's no value to trying a ketogenic diet, or to trying intermittent fasting.

I have a client who lost around 100lbs on an intermittent fasting/modified ketogenic protocol.

I have friends who have cleaned up autoimmune issues and are enjoying a much higher quality of life by switching to a ketogenic diet. 

Side note: making recommendations for nutritional interventions to aid with medical issues is outside of the professional scope of practice of a personal trainer. We simply don't have the requisite education to make those types of changes safely.

It's easy to see why guru's are pitching keto as a cure-all; but it isn't really that cut-and-dry, as evidenced by the scientific literature (not some "expert's" blog or infographic, void of citation and, y'know...any evidence to support their claims).

According to the Journal of the International Society of Sports Nutrition's Position Stand on diets and body composition (referenced earlier): "A wide range of dietary approaches (low-fat to low-carbohydrate/ketogenic, and all points between) can be similarly effective for improving body composition, and this allows flexibility with program design."

Bikini pro/health psychology Master's candidate/all-around flexible dieting badass Sohee Lee won her pro card in Bikini competition while eating a snickers bar every day of her prep leading up to the competition. Go figure. 


Live your damn life how it works best for you. Just because someone leaner than you told you that you have to do things a certain way, doesn't mean that it's the only way.

You can make health and fitness fit into the already-established rhythm your life (rather than making your entire life about health and fitness for as long as you can before burning out and then going back to the old way).

  • If you want to burn through your body fat, your primary objective should be to create a sustained caloric deficit through a combination of diet and exercise. The opposite is true if you want to gain weight.

  • Aim to eat a variety of mostly whole, unprocessed foods.

  • If you find yourself in a situation where the only choice is to eat a slice of pizza or to suffer in the corner while sipping water and eating nothing--eat the damn pizza without shame or guilt. Then get right back to your whole foods as soon as you can.

The Caveat...

In the very beginning stages of transitioning to living a healthier lifestyle, some people find it more helpful to be extremely structured and rigid in their approach to diet and training. 

They need to be told exactly what to do, how to do it, and when to do it. They don't care much about why they're doing it, though they should. 

If you're just starting out and you feel like you need more structure than what flexible dieting provides, there's nothing wrong with that.

If you're in a place where you literally cannot believe that you can have your cake and eat it too (in controlled amounts, once-in-a-while), then you're not ready for flexible dieting. 

Do what you think you need to do. If it works for you, keep doing it until it doesn't work anymore. That time will come. 

Start where you are and work with what you have. But don't stay there. You can't stay there forever. Life is always changing, and we must change with it. We're either moving forward or moving backward.

As you evolve, your approach to improving your health and fitness needs to evolve as well.

Flexible Dieting In Action:

My puppy mama/girlfriend/life partner Emily is vlogging about her flexible diet lifestyle leading up to her best friend's wedding in April. If you want practical examples of how to apply this stuff in the real world, check it out:



  1. Ng, J Y, et al. “Self-Determination Theory Applied to Health Contexts: A Meta-Analysis.” Perspectives on psychological science : a journal of the Association for Psychological Science., U.S. National Library of Medicine, July 2012, www.ncbi.nlm.nih.gov/pubmed/26168470.

  2. McSpadden, Kate E., et al. Appetite, U.S. National Library of Medicine, 1 Jan. 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC4684708/.

  3. Aragon, Alan A., et al. “International society of sports nutrition position stand: diets and body composition.” Journal of the International Society of Sports Nutrition, BioMed Central, 14 June 2017, jissn.biomedcentral.com/articles/10.1186/s12970-017-0174-y.

  4. Patel, Examine.com Kamal. “Is low-Carb really the best weight loss diet?” Examine.com, Examine.com, 3 Sept. 2014, examine.com/nutrition/is-low-carb-really-the-best-weight-loss-diet/.

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