Diet guide
Flexible Dieting (IIFYM): Macros First, Food Second
In short
Flexible dieting, or IIFYM (if it fits your macros), sets daily calorie and macro targets and lets any food count as long as the day lands inside them.
By CalorTracker Team. Published .
How flexible dieting works
IIFYM treats the day as a budget. You get a calorie target and a protein, carbohydrate and fat target, and no food is banned. A bowl of rice and a slice of cake are both items to log, and the question is whether the sum fits. The appeal is that it makes eating out, social meals and favourite foods easier to keep.
The label is shorthand for a method, not a claim that food quality is irrelevant. Most people who use it eat mostly whole foods and keep room for a few treats, which is the practical meaning of flexible.
Setting up the budget
Begin with a calorie target from the TDEE and deficit calculators. Then set protein from your weight and goal, fat as a share of calories, and carbohydrate as the remainder, which the macro calculator does in one step. Each gram is worth four, four or nine calories, so every food on the log changes the three numbers in a known way.
Protein is usually the one to hit, calories the one to stay near, and carbohydrate and fat the ones that trade against each other. Cutting and bulking versions of the calculator shift the target for each goal.
Fitting foods in without losing the plot
Plan the anchors early in the day, then see what is left for the flexible part. A treat that is mostly carbohydrate and fat will leave little for protein, and the log shows that clearly. Doing the arithmetic before you eat is what separates flexible dieting from just eating anything.
A weekly view helps, since a single heavy day can be balanced across the week. Do not chase exact daily numbers when your estimates are rough.
Foods that fit, per 100 g
Flexible dieting is about trade-offs, so the table pairs staples with a few treats. Compare how much protein each calorie buys.
| Food | Calories | Protein (g) | Carbs (g) | Fat (g) | Fibre (g) | Note |
|---|---|---|---|---|---|---|
| Chicken Breast (Roasted) | 165 | 31 | 0 | 3.6 | 0 | A protein anchor for the day. |
| White Rice (Cooked) | 130 | 2.7 | 28.2 | 0.3 | 0.4 | A carbohydrate base that is easy to weigh. |
| Greek Yogurt | 97 | 9 | 4 | 5 | 0 | A protein snack that doubles as dessert. |
| Banana | 89 | 1.1 | 22.8 | 0.3 | 2.6 | A quick carbohydrate. |
| Peanut Butter | 598 | 22.2 | 22.3 | 51.4 | 5 | Fat and calories in a spoon. |
| Dark Chocolate (60-69% Cacao) | 579 | 6.1 | 52.4 | 38.3 | 8 | A treat that is mostly fat and carbohydrate. |
| Ice Cream (Vanilla) | 207 | 3.5 | 23.6 | 11 | 0.7 | A treat that fits when you plan for it. |
| Cheese Pizza | 266 | 11.4 | 33.3 | 9.7 | 2.3 | A restaurant favourite with a wide range of estimates. |
| Eggs | 143 | 12.6 | 0.7 | 9.5 | 0 | A protein anchor with fat. |
Values are USDA FoodData Central figures for the food as listed, per 100 g. Each food name opens its own page with portions and every nutrient.
Calculators for this way of eating
These run on the same formulas as the rest of the site, so the numbers match what you see in the app.
- Macro CalculatorSplits a daily calorie target for your goal (lose, maintain or gain) into grams of protein, carbs and fat.
- Cutting Macro CalculatorWorks out the calories for a cut at a deficit you choose, then sets protein by body weight, fat as a share of calories and carbs for the rest.
- Bulking Macro CalculatorWorks out the calories for a bulk at a surplus you choose, then sets protein by body weight, fat as a share of calories and carbs for the rest.
- TDEE CalculatorEstimates the calories you burn in a day: your BMR from the Mifflin-St Jeor equation, multiplied by an activity factor.
Food lists to browse
Ranked tables of foods by a nutrient, computed from the same USDA data.
Side-by-side food comparisons
Two foods at the same weight, so a swap is one glance.
Read next
Guides from the CalorTracker blog.
Terms used on this page
Short definitions with worked examples.
Safety and who this is not for
Detailed macro tracking suits some people and not others. If counting grams makes eating stressful, or you have a history of disordered eating, stop and talk to a professional. Hitting your macros with highly processed food does not make the rest of the day balanced.
This page is general information, not medical advice. If you have a medical condition, take medication, are pregnant or are under eighteen, talk to a doctor or registered dietitian before you change how you eat.
Tracking flexible dieting (iifym) in CalorTracker
- Set your goal and the app creates calorie, protein, carbohydrate and fat targets you can edit.
- Log a meal by photo, text or voice and read the macro estimate on the review screen before saving it.
- Watch the dashboard's remaining macros before you choose the next meal, and ask Pepperly what would fit.
Flexible dieting (IIFYM): common questions
Does IIFYM mean I can eat anything?
How exact do the macros have to be?
Sources
- Burke LE, Wang J, Sevick MA. Self-monitoring in weight loss: a systematic review of the literature. J Am Diet Assoc. 2011;111(1):92-102.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005.
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018;52(6):376-384.
- Food values: USDA FoodData Central, as described on how we calculate. Every outside source we use is on sources.
Count flexible dieting (iifym) without the arithmetic
Log a meal from a photo, by text or by voice, check the estimate, and watch the day against your own targets. Free to start, no card needed to explore.
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