I eat burgers almost every day. Sometimes two for dinner. With the bun, cheese, mayo. Everything.
And I'm at 14% body fat.
Before you scroll away: no, it's not genetics. Not Ozempic. Not some 30-day crash diet. It's nearly two years of a method I learned through trial and error — one that permanently changed my relationship with food.
That method has a name: flexible dieting.
In this post I'll explain what it is, how it works in practice, and why I believe it's the smartest approach for anyone who wants to lose fat, build muscle, or simply live well without giving up the foods they love.
What Is Flexible Dieting
Flexible dieting is a nutritional approach built on a simple premise: what matters isn't the food itself, but what it represents in terms of macronutrients and calories within your plan.
In other words: you know your macros, you set your targets, and you have complete freedom to choose the foods that fill those numbers. Chicken and sweet potato or a homemade burger? Both work — as long as they fit your strategy.
This is radically different from traditional diets that hand you a list of allowed and forbidden foods. In flexible dieting, nothing is forbidden. Everything can be fitted in.
Why Restrictive Diets Fail (And Flexible Dieting Doesn't)
Before getting here, I spent years trying increasingly restrictive diets. Cut carbs. Cut fat. Intermittent fasting. I'd lose weight fast — and gain it all back within weeks.
I wasn't weak-willed. The problem was structural.
Here's what happens in your brain when you restrict too much: the greater the caloric and dietary restriction, the greater the urge to break the diet. And when you break it, it's usually with exactly the most calorie-dense, hyper-palatable foods you were avoiding.
Flexible dieting solves this in two ways:
First: when you know you can eat what you love tomorrow, eating well today becomes much easier. Food loses the emotional power that restriction creates.
Second: having a planned free meal in your cycle — weekly or bi-weekly depending on your stage — isn't weakness. It's strategy. It increases plan adherence and, as I'll explain further ahead, has a real physiological role for anyone in prolonged caloric deficit.
The result? More consistency. And consistency is the only factor that truly determines long-term results.
The 3 Pillars of Flexible Dieting
1. Know Your Macronutrients
Macronutrients are the three main components of everything you eat: proteins, carbohydrates, and fats. Each has a specific function in your body and a caloric value per gram.
To apply flexible dieting, you need to know your target for each one — and that depends on your goal (fat loss, muscle gain, maintenance), your weight, height, activity level, and metabolism.
The calculation exists and it's not complicated. There are scientifically validated formulas for this — like the Mifflin-St Jeor equation for calculating your basal metabolic rate. NutraFlex runs this calculation automatically during onboarding, but you can also find calculators online.
One golden rule I live by: protein is the most important macro to hit consistently. Maintaining at least 1.6g of protein per kg of body weight is fundamental to preserving and building muscle mass — even if you don't lift weights. Protein also increases satiety and has a higher thermic effect than other macros, meaning your body burns more energy just to process it.
Carbohydrates and fats have more flexibility. You can shift between them as long as you maintain your total daily caloric target. More carbs means more available energy for training. More fat means more satisfying meals. The balance depends on your lifestyle and preferences.
2. Have a Tracking Tool
This is the point where I see most people fail — or simply give up.
Without tracking, you're shooting in the dark. You think you ate well, but without real numbers you have no way of knowing if you're within your target, above, or below. And without knowing where you are, you can't adjust.
Think of it this way: a doctor doesn't prescribe treatment without test results. An engineer doesn't build without measurements. Why would you build your nutrition on guesswork?
Tracking doesn't need to be perfect. You don't need to weigh every gram of food forever. The goal is to have a real baseline — staying around 90% within your plan is already enough to produce consistent results.
What you need is a tool that makes tracking easy enough that you actually maintain the habit. The more friction, the lower the adherence. That's why NutraFlex was built to accept logging by photo, free text, barcode, or manual entry — you choose whatever works best for you in the moment.
3. Learn Through the Process
This is the benefit nobody talks about — and for me it was the most transformative.
When you start tracking what you eat, you inevitably start learning the nutritional value of foods. Not in a boring, rote memorization way — in a practical, hands-on way.
Over time, you start making smarter choices automatically. You know that seemingly innocent snack has 600 calories. You discover that a simple ingredient swap in your favorite burger maintains the flavour and cuts 200 calories. You learn to cook in ways that fit your diet without losing enjoyment.
This is nutritional autonomy. You stop being passive — someone who simply follows what a meal plan says — and become the owner of your choices. With real knowledge, not guesswork.
The Free Meal: Why It's Part of the Plan, Not a Weakness
Many people treat the free meal as an admission of weakness. "I couldn't resist." In flexible dieting, it's the opposite: it's a strategic tool.
But there's an important distinction depending on where you are in your journey:
If you're just starting out or still at a higher body fat percentage: the free meal needs to be approached carefully. It needs to be genuinely just one meal — not a full cheat day. If you're running a 200-calorie daily deficit and have a free meal with 2,000 extra calories, the weekly math simply doesn't work. The effect is diluted or erased.
If you've been dieting consistently for a prolonged period: the free meal is essential — and it has physiological backing. After weeks in a caloric deficit, your body begins adapting by reducing energy expenditure. A more calorie-dense meal, especially rich in carbohydrates, replenishes muscle glycogen and signals to the body that there's no scarcity. This prevents your metabolism from slowing too much and hitting a plateau.
For those looking to build muscle, the logic is similar: in some cases, a free meal every 3 days may be recommended to break a plateau and give the body the extra fuel it needs to build muscle.
The free meal, when applied correctly, increases plan adherence, has physiological benefit, and keeps you sane. It's part of the strategy.
How to Start With Flexible Dieting
If you've never done this before, here's a simple path:
Step 1: Calculate your macros.
Use an online calculator or go through NutraFlex onboarding — it uses the Mifflin-St Jeor formula to calculate your basal metabolic rate and sets your macros based on your goal.
Step 2: Start tracking what you already eat.
Before changing anything, log your current eating for 3 to 5 days. You'll be surprised by what you discover about your habits.
Step 3: Adjust gradually.
Don't try to change everything at once. Start with the most important macro: protein. Make sure you're hitting your daily protein target. Everything else naturally adjusts around it.
Step 4: Trust the process.
The first few days are the hardest — not because the diet is tough, but because learning to use the tool and understand food takes time. After 2 to 3 weeks, it becomes automatic.
Step 5: Evaluate and adjust every 2 weeks.
The plan that works at the start may not work after a month. Your body changes. Your routine changes. Your plan needs to keep up. That's why the bi-weekly check-in exists — it's the moment to look at the real numbers, evaluate actual progress, and recalibrate whatever's needed.
What Flexible Dieting Is Not
Worth clarifying to avoid misunderstandings:
It's not eating anything in any quantity. You still need to respect your caloric and macro targets. The freedom is in the food choices, not in the absence of limits.
It's not easy in the beginning. It requires focus, practice, and knowledge. But unlike restrictive diets, it gets easier over time — not harder.
It's not the same for everyone. Your macros are unique. Your routine is unique. Your goal is unique. Flexible dieting works precisely because it adapts to you — not the other way around.
Why I Built NutraFlex
After years of applying these principles in my own life — going from 103 kgs and 42% body fat to where I am today — I realised that the biggest obstacle for most people isn't a lack of information.
It's the lack of a tool that makes the process simple enough to sustain long-term.
The apps I used were static. They gave me a plan and disappeared. When I plateaued, they couldn't tell me why. When my routine changed, the plan became obsolete.
I wanted a coach — someone who genuinely followed along, asked questions, adjusted the plan based on what was actually happening. I couldn't find one. So I built it.
NutraFlex is exactly that: an AI coach that applies the principles of flexible dieting to your real routine. It logs your meals however is easiest for you, monitors your macros in real time, checks in every 14 days, and rebuilds your plan based on your actual progress.
If you made it here, you're ready to start.
👉 Try NutraFlex now at nutraflexapp.com
Atila Oliveira is a Senior Software Engineer and founder of NutraFlex. He lost more than 30 kgs applying the principles of flexible dieting and built NutraFlex to make this method accessible to anyone.