TL;DR
ChatGPT is good at building a meal plan and talking through your choices, but on its own it isn’t a dependable food diary. Use the prompts below to plan, and keep the record in a tracker like Calorie Cub. ChatGPT can also connect to Calorie Cub directly at https://mcp.caloriecub.com/mcp, but OpenAI limits that by plan: Business, Enterprise, and Edu can log, Pro can only read, and other plans aren’t listed.
What ChatGPT can and can’t do for a diet
It’s useful for the thinking: turning a goal into a daily target, planning a week of dinners around foods you like, writing a grocery list, or finding a lighter version of a meal.
It’s weak at the bookkeeping. Describe the same meal twice and you can get two different calorie estimates. A chat also isn’t a ledger, so it’s easy to lose count across days. Use ChatGPT for the plan and something else for the record.
Getting started with no connection
A few requests to try on any ChatGPT plan. Swap in your own details:
- •“I’m 5’6”, 170 pounds, and walk most days. I’d like to lose about a pound a week. Estimate a daily calorie and protein target, show your math, and tell me what could make the estimate wrong.”
- •“Plan five dinners at around 600 calories using chicken, rice, and frozen vegetables, then write the grocery list.”
- •“I don’t like fish and I only have 20 minutes to cook. Swap anything in this plan that doesn’t fit.”
- •“I ate way more than I planned tonight. Without telling me to skip meals, what’s a sensible way to handle tomorrow?”
- •Attach a photo of a menu: “Which three options here are probably the lightest, and what could I ask them to change?”
If you plan to keep coming back, make a ChatGPT project and put your goal, allergies, and food dislikes in its instructions so you don’t retype them.
Copy full diet plan and meal plan prompts ›Treat its calorie numbers as estimates
A target from ChatGPT is a starting guess, not a prescription. Your weight trend over a few weeks will tell you more than the formula did.
For the foods themselves, use a source you can check. Calorie Cub’s catalog is built from USDA data and restaurants’ own published nutrition, and every food is labeled official, reviewed, or estimated.
What studies say about ChatGPT’s calorie accuracy ›Browse restaurant nutrition facts ›Can you connect ChatGPT to your food diary?
A connection through MCP lets ChatGPT read your real diary and totals instead of guessing. What you can do depends on your ChatGPT plan, according to OpenAI’s help page on custom MCP servers:
- •Business, Enterprise, and Edu: full support on the web, including logging. On Business, only an admin or owner can create the connection; on Enterprise and Edu, an admin can grant that to members.
- •Pro: you can connect, with read and fetch permissions only. ChatGPT can read your diary but can’t log to it.
- •Plus, Free, and other plans: OpenAI’s page doesn’t list custom connections, so expect the option to be missing.
Calorie Cub isn’t listed in ChatGPT’s plugin directory. We’ve submitted it, but it hasn’t been approved, so for now a custom connection is the only route.
How to connect, if your plan allows it
- 1.In ChatGPT on the web, go to Plugins. OpenAI’s help page says custom connections are web only.
- 2.Select the plus button, then Add custom MCP server.
- 3.Name it Calorie Cub and enter https://mcp.caloriecub.com/mcp under Connection, with OAuth for authentication.
- 4.Check “I understand and want to continue,” select Create as a plugin, sign in to Calorie Cub, and approve access.
- 5.Install the plugin, start a new chat, type @, and select Calorie Cub.
ChatGPT applies your @ selection to that one message, so mention Calorie Cub again when a follow-up needs fresh numbers. It may also ask you to confirm before it changes anything.
OpenAI renames these menus from time to time. If a label doesn’t match, look for the option to add a server by URL.
Prompts once ChatGPT is connected
- •“@Calorie Cub What did I eat yesterday, and how close was I to my goals?”
- •“@Calorie Cub Compare my calories and protein this week with last week, then suggest one small change.”
- •“@Calorie Cub How much do I have left today? Suggest a dinner that fits.”
- •“@Calorie Cub Show my weight for the last month next to my average calories.”
- •With write access: “@Calorie Cub Log two scrambled eggs and a banana for breakfast.”
If your plan can’t connect
You can still use both. Log in the Calorie Cub app on the web or iPhone, then bring ChatGPT a summary when you want a review: export your data as JSON from Settings, and paste the part you want it to look at. Remember that whatever you paste goes to OpenAI, and the copy is out of date after your next meal.
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.
What Calorie Cub costs
Tracking in the Calorie Cub app is free with no time limit, and the free plan lets one assistant read your diary. Logging, editing, and setting goals by chat is part of Pro: $6.99 a month, or $39.99 a year with a 3-day free trial. Your assistant’s own subscription is separate.
Questions people ask
Can ChatGPT make a diet plan?
Yes, it can draft a meal plan around your goal, schedule, and tastes. Check the calories against a real source, because its numbers are estimates.
Can ChatGPT count my calories?
It can estimate calories in a conversation. It can’t keep a dependable running total on its own. For that it needs a tracker, either connected or alongside it.
Can ChatGPT help you lose weight?
It can help with planning and staying accountable, but the results come from what you actually eat and do. It doesn’t replace advice from a clinician.
Does Calorie Cub work with ChatGPT Plus?
As of this update, OpenAI’s page doesn’t list custom MCP connections for Plus, and Calorie Cub isn’t in the plugin directory yet. You can use the prompts above and track in the app.
Other guides
ChatGPT diet plan and meal plan prompts ›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
Sign in with Google, then log from the app or connect your assistant. No card needed.
How Calorie Cub works