AI nutrition plan: how your diet is calculated and built
An AI nutrition plan is a daily menu with calories and macros matched to your body and your goal. In Elvyfit, the math and the menu come from fixed rules run by code, while Elvy, the AI assistant, helps you ask for the plan and understand it. Here is how the numbers are made and what the plan cannot do.
What an AI nutrition plan is, and which part is the AI
An AI nutrition plan is not a magic menu. It is a set of instructions built on three concrete things: how many calories you get per day, how many grams of protein, fat and carbs, and which meals spread them out. In Elvyfit those three things come from rules that code runs, not from a language model improvising. That way your number is the same today as tomorrow, and it can always be explained.
The AI shows up somewhere else. Elvy, the assistant in the Elvy AI chat, can generate your meal plan when you ask for it, or suggest a macro reserve for a dinner out. It always labels itself as AI and it is not a person. The page about the AI fitness app explains where the AI steps in across the whole app, and where it does not.
How your nutrition plan is calculated step by step
The plan starts from your questionnaire: sex, age, height, weight, activity and goal. From there the code follows four steps, always in the same order. If you would rather do the math by hand, our guide on how to calculate your daily calories walks through it slowly.
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Basal metabolism
It is calculated with the Mifflin St Jeor formula from your sex, age, height and weight. This is the energy your body spends at rest.
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Daily energy use
The code adds what you do: average steps, type of job, extra activities, training sessions and the thermic effect of food at 10%. Or it uses activity factors from 1.2 to 1.9.
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Calories for your goal
With Definir, a moderate deficit is applied. With Ganar músculo, a light surplus of 150 to 300 kcal. Recomposición and Mantenerme start from your energy use as it is.
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Macros and extras
Protein at 1.6 g per kg of body weight, fat at 0.4 g per kg (0.5 when building, with a minimum of 15% of calories) and the rest in carbs. The plan adds 14 g of fiber per 1,000 kcal and a water target of 35 ml per kg, between 2 and 4 liters.
These are starting values, not a diagnosis. The weekly adjustment corrects whatever your real body asks for.
Safety floors that nobody can override
A plan that can be forced tends to end badly, so some limits cannot be changed by you or by the AI. The fat loss goal has its own page, the fat loss app.
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Calorie floor
It never drops below the higher of your basal metabolism and 1,500 kcal for men or 1,200 kcal for women.
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Capped pace
Weight loss is limited to 0.5 to 1% of body weight per week, with a maximum deficit of 25%. Weight gain is limited to 0.5% per week.
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Low BMI
With a BMI under 18.5 and a goal of losing weight, the plan is forced to maintenance.
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Health screening
With pregnancy, breastfeeding or an eating disorder, nutrition stays at maintenance and you are told to see a professional.
Meal variants, the shopping list and eating out
On the Free plan you get one option per meal. With Plus you get five variants per meal and batch cooking. The weekly shopping list comes straight from your plan, grouped by category, and it is free. Swapping the foods on that list is a Plus feature.
For the day you eat out, the feature called «Hoy como fuera» (the app is in Spanish) reserves macros up to 12 hours ahead, with a band of plus or minus 15%. To log what you actually eat, the meal and macro tracking includes a search bar and a barcode scanner.
Weekly adjustment: when your plan changes
Your plan does not move because of one bad day. The code decides it from your weekly report, and only when the data is solid enough.
| Condition | What the code requires |
|---|---|
| Logged data | 5 of the last 7 days with meals logged and 4 weigh ins per week |
| Deviation | A weight trend more than 25% away from the target pace for 2 weeks |
| Size of the change | Between 100 and 200 kcal, never repeated in the same week |
| Safety | Paused when there are signs of disordered eating |
Every adjustment is recorded and you can undo it. Free includes 2 reports with adjustment. Plus gives you unlimited reports.
Honest limits: what this plan is not
It is not a registered dietitian and it does not replace one. It does not diagnose, does not treat any condition and is not a medical product. If you have diabetes or another medical condition, if you are pregnant, or if you have a history of an eating disorder, talk to a professional before following any eating plan, this one included.
The 334 foods in the catalog carry estimated values and are marked as unverified. The app is only in Spanish for now, and you must be 18 or older to use it.
If your goal is to gain weight as muscle, take a look at the muscle building app page.
Frequently asked questions
Is the meal plan created by AI or by a program?
It is created by code using rules and 36 meal templates, scaling the grams until calories and macros fit within a tolerance of plus or minus 5%. The AI, Elvy, can request it in chat and explain it, but it does not invent the numbers. The calculation starts from the Mifflin St Jeor formula.
How much does the nutrition plan cost and what does the Free plan include?
Free includes the basic diet with one option per meal, the weekly shopping list and meal logging with unlimited history. Plus costs €19.99 a month or €199.99 a year, adds five variants per meal and comes with 7 days of trial without a card. You buy it only inside the app.
Does it replace a registered dietitian?
No. It is a general guideline for healthy adults, built with well known formulas, and it does not diagnose or treat anything. With a medical condition, pregnancy, breastfeeding or a history of disordered eating, check with a health professional first.
Can I use the plan if I have allergies or follow a vegan diet?
Yes. The questionnaire collects your eating pattern (omnivore, vegetarian, vegan or pescatarian), the 14 EU allergens plus lactose, and the foods you dislike. Allergies are treated as a strict exclusion, but always read the labels on what you buy.
What happens to my health data and the AI?
Your data lives on EU servers, and health data is used only with your explicit consent. The AI consent is optional and can be withdrawn in Settings, Privacy. Your name and email never travel to the chat, and you can export or delete everything.
Is the app available in English?
Not yet. The app is only in Spanish from Spain for now, even if your phone is set to another language. The numbers and rules are identical for all users, and this website is available in English so you can see how it works before downloading.
Get a plan built on rules you can understand
Download Elvyfit, answer the questionnaire and get calories, macros and a menu.