How many calories should you eat on Ozempic (semaglutide)?

By the UseBite team · General information, not medical advice

GLP-1 medications like Ozempic, Wegovy and Mounjaro quiet the food noise. Many people on them go from 2,500+ calories a day to barely 1,000 — without trying. That raises a real question: if the drug is doing the work, how much should you actually eat? And can you eat too little?

Yes, you can. This guide gives you the numbers.

Why eating too little backfires

When intake drops far below what your body needs at rest (your basal metabolic rate, BMR), three things tend to happen:

• You lose muscle, not just fat. Studies of GLP-1 weight loss suggest a meaningful share — in some analyses up to 25–40% — of the weight lost can be lean mass. Muscle is what keeps your metabolism high; losing it makes every future kilogram easier to regain.
• Your body adapts. A very aggressive deficit makes your body more efficient — you burn less at rest, move less without noticing, and hunger hormones ramp up. This is a big part of why weight rebounds after stopping a crash approach.
• You feel terrible. Fatigue, dizziness, hair thinning, constipation and gallstone risk all rise with sustained very-low intake.

As a rule of thumb, most adults should not go below roughly 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision. Below your BMR is almost always counterproductive.

Setting your own number

The medication changes your appetite; it does not change the math of energy balance. A sensible target on a GLP-1 looks like this:

1. Estimate your maintenance calories (TDEE). That is your BMR (from your age, sex, height and weight) multiplied by your activity level. Most online calculators do this in seconds.
2. Subtract a moderate deficit — 300 to 500 kcal.That produces roughly 0.3–0.5 kg of fat loss per week, which is the pace that best preserves muscle. The drug will often make even this moderate deficit effortless.
3. Floor it at your BMR. Never target below what your body burns at complete rest.
4. Adjust from real data, not vibes. Weigh yourself daily, average over weeks, and adapt: losing faster than ~0.7 kg/week? Add food. Nothing moving for 3+ weeks despite honest tracking? Trim slightly or move more.

Protein is the non-negotiable

With a smaller appetite, every meal has to earn its place. Protein first: aim for roughly 1.2–1.6 g per kg of body weight per day (a 80 kg person: ~100–130 g). Protein preserves muscle in a deficit, keeps you full longest, and has the highest thermic effect of any macro. When you can only eat small amounts, protein is what makes those calories count.

Why tracking still matters on a GLP-1

A common trap: “the drug suppresses my appetite, so I must be in a deficit.” Not necessarily — calorie-dense small portions (nuts, cheese, sauces, liquid calories) can quietly keep you at maintenance even when you feel like you are eating nothing. People who stall on GLP-1s are usually surprised by what honest tracking reveals. Tracking also gives you the early-warning signal for the opposite problem: intake that has drifted too low.

This article is general information, not medical advice. Talk to your prescriber before changing your diet on any medication.