In short
There is no calorie number this article can responsibly give you, and that is not evasion. On a medication that suppresses appetite, the realistic risk is.
By Alsen Walker · Updated September 19, 2026
There is no calorie number this article can responsibly give you, and that is not evasion. On a medication that suppresses appetite, the realistic risk is eating too little rather than too much, and a number published online becomes a target to get under. Your prescriber or a dietitian can set one for your body, your activity and what you are being treated for.
If you came here looking for the lowest number you can safely eat, please stop and speak to someone. That question is a warning sign in itself, and it is common on these medications precisely because not eating becomes easy.
The National Alliance for Eating Disorders helpline offers support, and your prescriber needs to know if this is where your thinking has gone.
For how this fits alongside the rest of eating and training on a GLP-1, see Eating and Training on a GLP-1: The Complete Guide.
Why counting is the wrong tool here
On most weight loss approaches, the challenge is restraint. Here the medication does the restraining, and often does more of it than intended.
People routinely discover, when they track for a few days, that they are eating far below anything a clinician would have recommended. Not deliberately. Appetite simply stopped prompting them.
Adding a calorie ceiling on top of that solves a problem you do not have while making the real one worse.
The signs that intake has gone too low
These matter more than any number, because they are your body reporting directly.
Feeling cold constantly. Hair shedding several months in. Exhaustion that rest does not fix. Dizziness on standing. Losing strength. Periods becoming irregular or stopping. Poor concentration and low mood.
Several of these together is not a coincidence and is worth raising promptly.
What to watch instead of calories
Protein. The thing most worth tracking if you track anything, because it protects muscle and it is the first casualty when appetite goes.
Fluid. Urine colour and frequency tells you more than a volume target would.
Rate of loss. Faster is not better. If weight is falling very quickly, that is a reason to talk to your prescriber, not a success.
Function. Strength, energy, ability to do what you normally do. These fall before the scale tells you anything useful.
If you want a number anyway
That is a reasonable thing to want, and the right source is a person who knows your history.
Ask your prescriber or a dietitian for a minimum intake rather than a maximum. That framing matters. On these medications the useful figure is the floor you should not go under, not the ceiling you must stay beneath.
Bring a few days of honest tracking to that conversation. It makes the answer specific rather than generic.
Tracking, if you do it
For a few days, to see where you actually are, it is genuinely useful. As a permanent daily habit it becomes a preoccupation for some people, particularly anyone with a history of disordered eating.
If logging is creating anxiety, or you feel you have failed by eating more than a figure, that is the point to stop and talk to someone.
What to watch instead of calories is protein, fluid and the physical signs in the signs you are undereating. If the question behind this is how little you can eat, that is worth taking to someone.
Frequently asked questions
Why will you not give a number?
Because the appropriate figure depends on your body and circumstances, and because on this medication a published number functions as a target to eat below.
Will eating too little slow my weight loss?
It costs muscle, which lowers your energy needs and makes plateaus and regain more likely. It also makes you feel considerably worse.
Should I eat if I am not hungry?
Yes. Your requirements do not disappear with your appetite.
Do I need to track at all?
No. Many people do better watching protein and function instead.
What if I cannot eat enough?
Tell your prescriber. There are options, including adjusting the dose or pace.
Is very fast weight loss a good sign?
No. It usually means more muscle lost and is worth raising.
Sources and further reading
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH). Treatment for overweight and obesity. www.niddk.nih.gov
- MedlinePlus (US National Library of Medicine). Semaglutide injection: drug information. medlineplus.gov
- MedlinePlus (US National Library of Medicine). Tirzepatide injection: drug information. medlineplus.gov
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH). Prescription medications to treat overweight and obesity. www.niddk.nih.gov
GLP1Hub content is for general information and is not medical advice. Prices and coverage rules change often, so confirm current details with the provider, your insurer and your prescriber. See our editorial standards and medical disclaimer.
