TL;DR
A good diet prompt gives ChatGPT your goal, your real constraints, and the format you want, and asks it to show its assumptions. Copy any prompt below and replace the parts in [brackets]. They work on any ChatGPT plan with nothing connected, and in Claude, Gemini, or Grok too. Treat the calories it gives back as estimates.
What makes a diet prompt work
- •Your numbers: height, weight, age, activity, and the pace you want.
- •Your constraints: allergies, foods you won’t eat, budget, cooking time, and how many people you’re feeding.
- •The output you want: a table, a grocery list, or one meal at a time.
- •A request to show its assumptions, so you can catch a wrong portion before you follow it.
If you’ll keep using a prompt, paste your details into a ChatGPT project’s instructions once, then ask for each plan in a sentence.
Diet plan prompt
I'm [height], [weight], [age], and [activity level]. My goal is to [lose about a pound a week / maintain / gain slowly]. Estimate a daily calorie and protein target and show the formula you used. Then outline a simple way of eating I could follow for four weeks. I don't eat [foods], and I usually have [time] to cook. List what you assumed and what could make your estimate wrong. Don't recommend skipping meals, extreme restriction, or supplements.
Weekly meal plan and grocery list prompt
Plan [five] dinners and [five] lunches for [one person] at about [600] calories each, with at least [35] g of protein per meal. Use overlapping ingredients so little goes to waste, and keep the week under [$ budget]. I can't eat [allergies]. Show a table with the meal, portion sizes in grams or cups, and estimated calories and protein. Then write one grocery list grouped by store section.
Have a specific diet in mind? Add it in plain words, such as “Mediterranean-style” or “vegetarian.” If you’re following a diet for a medical reason, have a clinician or dietitian check the plan.
Weight loss coach prompt
Be a calm, practical weight loss coach. Ask me one question at a time until you understand my routine, what I usually eat, and where things tend to go wrong. Then suggest the two smallest changes likely to help, and how I'll know they're working after two weeks. No guilt, no extreme restriction, and no medical advice. Tell me to ask a clinician if something sounds medical.
Nutrition coach prompt for understanding food
Explain this in plain English as a nutrition coach, not a doctor: [paste a nutrition label, ingredients, or a question]. Tell me what stands out, what doesn't matter much, and what you're unsure about. If it depends on a health condition, say so instead of guessing.
Eating out prompt
I'm eating at [restaurant] tonight, and I have about [700] calories and [40] g of protein left. Suggest three orders and what to change about each. Tell me which numbers are from published nutrition and which are your estimates.
For chain restaurants, you can check its answer against published numbers.
Look up restaurant nutrition facts ›Calorie tracking prompt, and its limit
For this chat, keep a running food log for today. When I tell you what I ate, list each food, the portion you assumed, and estimated calories and protein, then show my total against [2,000] calories and [150] g of protein. Ask me about the portion if I don't give one.
This works for a day, but the numbers are estimates, and a chat isn’t a dependable record across weeks. For a diary that stays put, connect your assistant to a tracker.
How accurate ChatGPT’s calorie estimates are ›Log meals by chat with a connected tracker ›Weekly review prompt
Here's my food log for the past week: [paste your log]. Don't judge it. Tell me my average calories and protein, which days were different and why they might have been, and one change to try next week. Point out anything that looks like a missing meal, so we don't draw conclusions from gaps.
If you track in Calorie Cub, you can export your data as JSON from Settings and paste the part you want reviewed. Whatever you paste goes to OpenAI.
Food diary, not medical advice
ChatGPT and Calorie Cub can help you keep track and think through options, but neither is a doctor or dietitian, and an assistant can be wrong with total confidence. If you’re pregnant, have diabetes or another condition, take weight-loss medication, or have a history of disordered eating, talk to a clinician before changing how you eat.
Questions people ask
What’s the best ChatGPT prompt for a diet plan?
One that includes your numbers, your constraints, and the format you want, and asks ChatGPT to list its assumptions. The diet plan prompt above is a good starting point.
Are these prompts free to use?
Yes. They’re plain text and work on any ChatGPT plan, with nothing to connect or sign up for.
Can I follow a meal plan from ChatGPT as written?
Treat it as a draft. Check the portions and calories against a real source. If you have a medical condition or dietary need, have a clinician or dietitian review it.
Do these work in Claude, Gemini, or Grok?
Yes. Nothing in them is specific to ChatGPT, though the results will differ between assistants.
Other guides
Use ChatGPT to help you diet ›Is ChatGPT accurate for calories? ›Use Claude to help you diet ›Use Gemini to help you diet ›Use Grok and Grok Bot to help you diet ›AI calorie counter: photo, voice, or chat ›How logging meals by chat works ›Try Calorie Cub free
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How Calorie Cub works