IIFYM — If It Fits Your Macros — is a flexible dieting approach that has replaced rigid meal plans for millions of people. The premise is simple: as long as your daily protein, carbohydrates, fat, and calories hit your targets, what you eat is up to you.
No forbidden foods. No cheat meals. No guilt over pizza — as long as it fits.
This guide explains IIFYM from scratch: what it is, how to calculate your targets, how to track it daily, and whether it actually works.
What Is IIFYM?
Traditional dieting assigns specific foods and meals. "Eat chicken and broccoli. No alcohol. No sugar." IIFYM inverts this: instead of restricting which foods you eat, you set macro targets and eat whatever you want within those numbers.
A person doing IIFYM with a 150g protein / 200g carbs / 55g fat target might eat:
- Breakfast: eggs and oats
- Lunch: a burger (logged and accounted for)
- Snack: protein bar
- Dinner: salmon and rice
The burger is fine. It just means dinner is adjusted to stay within the daily totals.
IIFYM works because:
- Calories and macros determine body composition — not food purity
- Dietary flexibility dramatically improves long-term adherence
- Eliminating guilt and "forbidden foods" reduces binge-restrict cycles
Does IIFYM Actually Work for Weight Loss?
Yes — the evidence is clear that flexible dieting approaches produce better long-term outcomes than rigid ones.
A 2002 study in the journal Eating Behaviors found that dietary restraint (rigid restriction) was associated with higher rates of overeating and worse dietary adherence compared to flexible dieting approaches.
Multiple subsequent studies have confirmed: the people who can occasionally eat pizza and still hit their goals are the people who maintain their diet longest.
IIFYM works for:
- Fat loss (maintain calorie deficit, hit macros)
- Muscle gain (maintain calorie surplus, hit macros — especially protein)
- Body recomposition (maintain maintenance calories, high protein)
- General health (when applied with some nutritional awareness)
IIFYM's limitation: It makes no distinction between whole foods and ultra-processed foods at equal macros. Someone eating 150g protein from processed meat products vs. lean chicken, fish, and legumes will have different satiety, micronutrient, and long-term health outcomes — even if the macros match. Most IIFYM practitioners address this by applying an informal "80/20 rule" — 80% whole foods, 20% flexible.
How to Calculate Your IIFYM Macros
Step 1: Find Your Calorie Target
Calculate your TDEE (Total Daily Energy Expenditure) based on age, weight, height, and activity level. Then adjust based on your goal:
- Fat loss: TDEE minus 300–500 calories
- Muscle gain: TDEE plus 200–300 calories
- Maintenance: At TDEE
Step 2: Set Your Protein Target
Protein is the most critical macro in IIFYM. Set it based on your bodyweight:
- Fat loss: 0.8–1.2g per pound of bodyweight (1.8–2.7g per kg)
- Muscle gain: 0.8–1g per pound of bodyweight
- Maintenance: 0.6–0.8g per pound
Step 3: Set Your Fat Target
Fat is essential for hormonal health. Set a minimum:
- Minimum: 0.3g per pound of bodyweight (0.7g per kg)
- Standard: 20–30% of total calories
Step 4: Fill the Rest with Carbohydrates
Once protein and fat calories are assigned, carbohydrates fill the remaining calories.
Example calculation — 80kg male, fat loss goal:
- TDEE: 2,500 calories → target: 2,000 calories (500 deficit)
- Protein: 176g × 4 cal = 704 calories
- Fat: 55g × 9 cal = 495 calories
- Carbs: (2,000 − 704 − 495) ÷ 4 = 200g carbs
- Final: 2,000 cal · 176g protein · 200g carbs · 55g fat
How to Track IIFYM Daily
Tracking is non-negotiable in IIFYM. Without it, you have no idea if "it fits your macros."
Use a macro tracking app:
NutriBalance is the best free option for Android. It lets you set fully custom macro targets in grams, tracks protein, carbs, fat, and fibre separately, and shows your running daily totals.
Logging tips for IIFYM:
- Use the barcode scanner for all packaged food
- Use the AI food label scanner for restaurant meals, international products, or anything without a barcode
- Log meals before eating (or plan your day in the morning) — this prevents going over budget
- Weigh food on a digital scale for accuracy on calorie-dense foods (peanut butter, cheese, oils)
Pre-logging: Many IIFYM practitioners log their entire day in the morning. This way you know exactly what to eat before you eat it, rather than trying to fit a late-night snack into an already-full macro budget.
IIFYM Food Examples
The point of IIFYM is flexibility, but these high-protein, high-volume foods are staples because they're efficient:
High-protein efficiency foods:
- Chicken breast (cooked): 31g protein / 165 cal per 100g
- Greek yoghurt (0% fat): 10g protein / 57 cal per 100g
- Cottage cheese: 11g protein / 98 cal per 100g
- Eggs: 6g protein each / 70 cal each
- Canned tuna: 25g protein / 116 cal per 100g
High-volume, low-calorie foods (fill you up without busting macros):
- Cucumber: 16 cal per 100g
- Lettuce: 15 cal per 100g
- Broccoli: 34 cal per 100g
- Strawberries: 32 cal per 100g
- Courgette/zucchini: 17 cal per 100g
The "fits your macros" foods (use sparingly to hit targets):
- Dark chocolate (fits if protein and fat budget allows)
- Pizza (fits if carbs and fat are managed for the day)
- Ice cream (a small portion can fit if macros allow)
Common IIFYM Mistakes
Mistake 1: Ignoring fibre Pure IIFYM tracks only protein, carbs, and fat. Adding fibre as a target (25–35g/day) improves satiety and digestive health without compromising flexibility.
Mistake 2: Eating 100% processed food because it "fits" Technically valid, but you'll be deficient in micronutrients, feel worse, and likely have poor satiety. Apply an 80% whole foods baseline before flexing.
Mistake 3: Not weighing calorie-dense foods A tablespoon of peanut butter by volume can range from 70 to 130 calories depending on how packed it is. Weigh everything with a scale until you develop accurate portion intuition.
Mistake 4: Abandoning tracking when it's inconvenient Restaurant meals and social situations feel hard to track — but they're exactly when accurate logging matters most. Use the AI food scanner or make a best estimate in the app. An imperfect log is better than no log.
Frequently Asked Questions
Is IIFYM the same as flexible dieting? Yes. IIFYM and flexible dieting refer to the same approach — meeting macro targets without restricting specific foods. IIFYM is the more colloquial term popularised in fitness communities.
Can you eat junk food on IIFYM? Technically yes — if it fits your macro targets. Practically, very calorie-dense foods make it difficult to hit your macros without going over calories. Most IIFYM practitioners eat mostly whole foods with strategic flexibility for social eating or enjoyment.
What app should I use for IIFYM? NutriBalance is the best free IIFYM app for Android. It allows fully custom macro targets, tracks all three macros separately, and has a barcode and AI label scanner for fast logging.
How long does IIFYM take per day? With a good app and barcode scanner, 5–15 minutes. Pre-logging your day in the morning reduces this to about 5 minutes.
Is IIFYM good for beginners? Yes — the flexibility makes it sustainable for beginners who might otherwise fail on rigid meal plans. Start with approximate targets and get more precise as you build the tracking habit.
Track your calories, macros, and streaks for free with NutriBalance — the gamified calorie tracker for Android.
