If It Fits Your Macros (IIFYM) is a diet and lifestyle that promises weight loss (and health) while still letting you eat anything.
IIFYM puts dietary flexibility first and foremost. It’s best known for not labeling any foods as “forbidden” or “allowed”.
But does this form of flexible dieting actually work?
Nearly a decade ago, I decided to try the diet myself to find out. Three years later, I noticed some definite pros and cons.
So in this article, I’ll share everything you need to know about IIFYM. How it works, the science behind the diet, the pros/cons, IIFYM alternatives, and a whole lot more.
By the end, you’ll know whether or not you should try this lifestyle.
What is IIFYM & How Does it Work?
IIFYM, or If It Fits Your Macros, is a personalized diet system that puts your macronutrient and calorie goals first. The three main macronutrients (”macros”) include protein, carbohydrates, and fats.
Every food we consume contains some ratio of these three.
The IIFYM theory states that as long as you consume the right quantities of each macro, then you can enjoy the freedom to eat any of your favorite “junk” foods and still make progress.
While it excels at flexibility, it has some drawbacks like overweighing the importance of quantity and underweighing quality.
The Basic Steps to Following an IIFYM Diet
The actual process of implementing IIFYM is pretty straightforward. Most of the work comes down to tracking your food.
Once you’ve done it for a while, you can estimate foods without needing to log anything.
Here’s a simple outline of how to follow IIFYM:
- Calculate your macros: Find your daily macronutrient needs based on factors like age, weight, activity level, and goals (more on this below).
- Track your food intake: Use a food diary or tracking app to monitor your daily intake of macros (proteins, carbohydrates, fats) and calories.
- Adjust as needed: Every month or so, review your progress and make adjustments to your macro goals based on results and feedback from your body.
This isn’t a quick-fix diet. You won’t drop 10 pounds every week.
Consistency is still key to great results. Share on XAlthough IIFYM allows flexibility, prioritize consuming nutrient-dense whole foods to support your overall health.
Many downplay the importance of food choice, but consuming enough micro-nutrients will reduce cravings and improve your long-term success.
In my opinion, optimizing micronutrients has a higher impact than macros.
Calculating your ideal macros & calories
When following IIFYM, you care the most about four metrics. These include total calories, carbohydrates, dietary fat, and dietary protein.
Your needs will vary dramatically from other people. Based on many factors, including:
- Age
- Gender
- Weight
- Goals
- Physical activity
- Genetics
- Health conditions
- Motivation
- Desired diet
- Height
Most people use a free online calorie & macro calculator to determine their needs. They generally account for many of the above factors.
Use one of these to calculate your approximate needs.
Note your results down, because they influence everything else.
While your results will vary, the approximate breakdown will look something like:
- Protein: 20-40% of total daily calories
- Fat: 20-35% of total daily calories
- Carbohydrates: 40-60% of total daily calories
That’s the easy part, next comes tracking your foods.
How to track your macronutrient intake
Logging, tracking, and optimizing your foods will seem daunting at first. Tedious too.
But you’ll quickly get the hang of it, and before long, won’t need to log everything.
Initially, I recommend using one of the following apps (from best to worst):
These apps have massive databases of foods, macros, and micronutrients. Cronometer’s the best because it has the most information about each food.
If you’ve read my guide on biohacking weight loss, you know that tracking your diet can boost your progress significantly.
You’ll probably want to grab a food scale and measuring cups to help you understand portions.
Again, once you learn to precisely quantify foods, you’ll be able to eyeball them and have an understanding of macros and calorie content.
When you start, you’ll probably be shocked at how hard it is to get enough high-quality complete protein. And how calorically dense restaurant foods are.
The Best IIFYM Foods For Each Macro
Most online guides allow low-quality foods, as long as you get enough of each macro.
So I’ve modified the general recommendations to include the most nutrient-dense (and least anti-nutrient) sources for each.
| 🍚 Carbs | 🥩 Protein | 🥑 Fats |
|---|---|---|
| Fruits | Beef | Avocado |
| Vegetables | Organ meat | Eggs |
| Root vegetables | Eggs | SMASH fish |
| White rice | Dairy | Olives |
| Legumes | Pork | Nuts (moderation) |
| Honey | Chicken | Seeds (moderation) |
| Seafood | Dark chocolate | |
| Whey | Full-fat dairy | |
| Spirulina |
I generally recommend focusing on protein as it’s the hardest to get adequate.
Clean sources of fat can be tricky too. Unlike protein and carbs, fat contains nine calories per gram (the former both contain four per gram). Going 50 grams of fat over your requirements will quickly put you in a caloric surplus (and weight gain).
Though these are some of the best food sources of each macro, you can use the tracking apps to make sure your meals align with your plan.
Benefits of the IIFYM Diet
The IIFYM diet and lifestyle have some advantages.
Here are the primary benefits and reasons people follow this way of eating.
Flexibility
The IIFYM diet gives you the flexibility to choose your desired foods. You only must meet your macronutrient and caloric targets. That’s all.
This makes it easier to stick to the diet long-term and accommodates your personal preferences.
Personalization
Like most modern diets, you can adapt it to match your goals and desired body transformation. All you do is adjust your macronutrient ratios and calories.
This allows you to use the same style of eating to both build mass/gain weight while burning body fat. Essentially, it’s a personalized approach to nutrition.
No restrictions
Unlike other diets, IIFYM does not restrict any specific food groups or particular foods.
As its name states, if the food fits into your macro plan, you can eat whatever you want. The flexibility and personalization of IIFYM make it more sustainable compared to restrictive diets.
Dieters often follow it long-term.
Psychological satisfaction
Food choice flexibility provides feelings of satisfaction and reduces the deprivation of traditional diets.
There’s a common saying that applies to all health topics… “that which we resist, persists”. That certainly applies here.
This can improve adherence and lead to a more positive relationship with food. It can also reduce unhealthy cycles of binge eating.
Education & awareness
To succeed with IIFYM, you must learn about calories, macronutrients, and their roles in the body. You also become great at approximating the nutrient levels of the foods you eat most often.
Here’s a quick guide to understanding food labels as additional information to your food tracking app.
Even if you stop following this way of eating, that nutritional knowledge will stay with you. Not only foods, but the impact of movement, metabolism, and much more.
Downsides of the IIFYM Diet
From my experience and research, IIFYM has far more drawbacks than benefits.
What follows are just a few of the most important considerations before starting this diet.
Dangerous nutrient deficiencies
Typical IIFYM diets lack nutrient density and often cause major vitamins, minerals, fiber, and micronutrient deficiencies.
In a pinch, we can easily get adequate macronutrients through meal replacement products. The exact right macros and calories to meet your needs.
However, try to live off those, and within a few months, your body will noticeably degrade.
Long periods without adequate micronutrients (and even fiber) can cause irreversible damage. Such as permanently eradicating keystone bacterial species from your gut microbiome.
Deficiency also makes you more susceptible to disease [R]. But it’s not just your health that can get damaged.
Long-term progress
Micronutrient deficiencies impair vital bodily functions.
Things like the production of brain chemicals (neurotransmitters), hormones, enzymes, cellular energy (ATP), protein synthesis, and fat burning (beta-oxidation).
Just a single deficiency can hurt your testosterone, growth hormone, and other anabolic processes throughout the body.
Since this diet completely neglects micronutrients, without special care, long-term issues often arise.
Even if it fits in your macros, IIFYM isn’t an excuse to make junk a large part of your intake.
Inaccurate targets
Influencers portray IIFYM as a scientific answer to the classic energy balance equation. The one that says:
Weight gain/weight loss = Calories Consumed Minus Calories Burned
AKA…
Weight change = CI – CO
Yet this is riddled with issues. First, macro calculators themselves are usually outdated, inaccurate, and lack scientific validity. So your entire personalized plan is built on a shaky foundation.
But then there’s the tracking itself. Apps suffer similar problems. Food and meal information in the app databases rarely match what you’re actually consuming.
Unless it’s highly processed food with a menu available online.
Even if you’re trying to eat clean at home, to get accurate results you need to manually weigh everything yourself.
Time-consuming
IIFYM takes time to learn. Especially when you’re just starting.
Fetching the food scale, taring the scale, weighing the food, and then logging everything consumes a ton of time.
Multiple times, for each food group, every day. As well as for drinks.
You’ll also want to track your energy expenditure.
That’s on top of IIFYM planning and adjusting.
It becomes less time-intensive over time, but it’s a lot of work upfront.
Obsession & disordered eating
Granular control and nutrition education is a double-edged sword. Helpful and empowering for most.
But like many diets, this way of eating can induce or exacerbate unhealthy relationships with food. If you tend to obsess or become fixated on things, IIFYM will likely make it worse.
If you’re unsure which camp you’ll fall into, tread lightly.
Ignores meal timing
IIFYM completely ignores one of the most important variables of healthy eating: timing.
The cleanest meal at a bad time (say, midnight) will cause more problems than a low-quality meal eaten during ideal hours (say, noon).
In fact, the same meal eaten at different times can elicit up to a 30% different blood sugar response.
And that’s just one parameter. Meal timing influences sleep, metabolism, growth, performance, and virtually every facet of optimal health.
Allows highly processed foods
The flexibility of IIFYM acts as both a pro and con. It doesn’t outright ban any particular foods or food groups. That’s also one of the downfalls.
IIFYM allows ultra-processed foods. That violates one of the only principles shared by virtually all successful diets that yield long-term results (for aesthetics and health).
Nutrition experts disagree about almost everything. They do, however, agree that ultra-processed food has no place in a healthy diet.
Even elite athletes see major health biomarker improvements when incorporating more whole, unprocessed foods.
While highly processed foods are fine for an occasional treat, they’re discouraged by virtually every successful long-term diet.
Variable satisfaction
Another item on both the pros and cons list. While allowing for junk foods daily, this diet also doesn’t satiate everyone.
This is because each macronutrient has a different effect on overall enjoyment and feeling full.
Carbohydrates, especially highly refined types, stimulate hunger again quickly. And many people experience “hangryness” if too much time passes between their final meal.
Protein induces long-lasting feelings of fullness. As does fiber. These each affect hunger hormones (ghrelin, leptin, PYY, CCK, GLP-1, insulin), energy levels, biomarkers like cholesterol, and your overall health.
When I ate high-carb, I hated the ravenous hunger driving me to find food every few hours.
Better Alternatives to The IIFYM Diet & Lifestyle
If IIFYM has more dangers and drawbacks than benefits, what simple ways of eating work better?
My favorite way of eating is to flip it around.
Instead, I prefer another form of IIFYM (“If It Fits Your Micros”).
By prioritizing micronutrients, you’re focused on choosing high-quality foods. The more nutrient-dense, the better.
One of the best reasons to do this comes down to hunger. Often, what feels like a ravenous hunger is really just the body seeking specific micronutrients.
Once you get enough, your appetite normalizes and you feel good. Making weight loss or muscle building far easier.
As a side effect, you’ll probably end up in a similar macronutrient ratio but without much effort. Macronutrient deficiencies are easy and much more obvious to fix too.
You can also remineralize yourself by adding in high-quality nutrients like:
The same apps that break down the macronutrient content of food (ie Cronometer) can also help you find the foods with the most micros.
Upgrading IIFYM for Health, Performance, & Optimal Body Composition
Lose weight while eating junk food?
Count me in!
IIFYM has plenty of appealing attributes.
I followed this way of eating for years. It’s certainly better than the Standard American Diet (ironically, abbreviated SAD).
For some people, it helps improve their health and transform their body.
Yet the progress usually plateaus as certain nutrient deficiencies worsen.
Doing it right requires attention to nutrient density. Which contradicts many of the top selling points of this diet.
When you get enough micronutrients, your entire body runs better and more efficiently. You feel and perform better too.
At the very least, if you decide to use IIFYM make sure to supplement micros. That way, you can offset the potentially irreversible long-term damage.
If you found this article helpful, I’d appreciate you sending it to a friend who’s considering IIFYM or sharing it on social media.
If you have any questions or personal experience, I’d love to hear from you. Drop a comment below!
