How Much Should You Eat on Mounjaro or Ozempic?

GLP-1 medications cut how much people eat by somewhere between 16% and 39%, so for most people the question stops being how to eat less. It becomes how not to eat too little. While you're losing weight, a sensible range is roughly 1,200 to 1,500 kcal a day for women and 1,500 to 1,800 for men, spread over three small meals and a snack, with protein first each time.

How much less you'll eat

The smaller appetite is the medication working. Across trials, GLP-1s reduce how much people eat by 16 to 39% compared with placebo, through less hunger, earlier fullness and fewer cravings. In one 20-week semaglutide trial, people offered as much lunch as they wanted ate 35% less than those on placebo: about 415 kcal against 640.

So eating less, the usual weight-loss advice, is the part the medication handles for you. What it doesn't do is make sure the smaller amount still covers what your body needs.

How many calories, roughly

You don't need to count calories every day on a GLP-1. But tracking for a few days early on shows whether you're in a sensible place, and the 2025 joint advisory from four US obesity and nutrition societies recommends checking intake with food logs or photos for exactly this reason. These are the reference points:

	Women	Men
Average needs to maintain weight	About 2,000 kcal	About 2,500 kcal
Typical weight-loss diet	1,200–1,500 kcal	1,500–1,800 kcal
Vitamins and minerals get hard to cover below	1,200 kcal	1,800 kcal

The first row is the NHS average; your own number depends on your size, age and how active you are. The second is the range US obesity guidelines usually set for weight loss, typically 500 to 750 kcal below what you'd need to maintain. The third comes from the advisory, which warns that the sharp drop in intake on these medications can leave people short of essential vitamins and minerals, especially below those levels.

For men, the whole typical weight-loss range sits at or below that 1,800 line, so what you eat matters even more. And if you're regularly eating under 800 kcal a day, you're in very-low-calorie-diet territory, which the same guidelines describe as something done under medical supervision. Tell your prescriber.

Can you eat whatever you want and still lose weight?

Often, yes, at least for a while, because you'll eat less of it. But what you eat decides what kind of weight you lose and how you feel while you lose it.

• Muscle. Some of the weight you lose is always lean tissue: in the STEP 1 trial of semaglutide, 38% of the weight lost was lean mass, which includes muscle. The advisory says how much depends partly on how hard you cut calories, how fast the weight comes off and whether you do strength training. More in muscle loss on a GLP-1.
• Nutrients. On a smaller intake there's little room for food that brings calories and not much else. The advisory recommends building meals around fruit, vegetables, whole grains, beans, lean protein, nuts and seeds, and cutting back on refined carbs, sugary drinks, processed meat, fast food and ultra-processed snacks.
• Side effects. Vomiting is more likely after large meals, and avoiding large or high-fat meals helps with diarrhea. See foods to avoid on a GLP-1.
• Later. The habits you build while the medication does the heavy lifting are the ones you'll rely on if you ever stop.

Why skipping meals backfires

With little appetite, it's easy to go most of the day without eating and barely notice. The advisory describes where that leads: for some people, undernutrition; for others, a rebound pull towards sugar and refined carbs once hunger finally arrives. Nausea also tends to strike in the morning or after long gaps without food, and some people get stuck in a loop where nausea stops them eating, which makes the nausea worse.

Long gaps carry another cost. When you go a long time without eating, or lose weight quickly, your liver releases extra cholesterol into your bile, the NIH explains, and losing weight very quickly may raise your chance of gallstones.

For people caught in the nausea loop, the advisory suggests breakfast, then a small meal every three to four hours, with enough to drink. If you forget to eat because you're never hungry, set a reminder. And even if you practise intermittent fasting, it recommends eating at regular times while you're on a GLP-1.

What a day of eating can look like

Here's a day built from four recipes on the site, each with protein first:

Meal	Recipe	Calories	Protein
Breakfast	High-Protein Greek Yogurt Bowl	295 kcal	26 g
Lunch	Chicken and White Bean Soup	235 kcal	30 g
Snack	Cottage Cheese Flatbread	155 kcal	20 g
Dinner	Lemon-Herb Baked Salmon with Greens	350 kcal	29 g
Total		1,035 kcal	105 g

The protein is right where it should be. The calories aren't: a day made entirely of lean, protein-first dishes can land under 1,200 kcal without feeling like you've skimped, which makes it an easy way to under-eat without noticing.

Closing the gap doesn't take much more food, just a few denser additions. A tablespoon of nut butter stirred into the yogurt, a slice of wholegrain toast (40 g) with the soup and 150 g (about 1 cup) of cooked rice with the salmon add about 390 kcal, taking the day to roughly 1,430 kcal and 116 g of protein. For most men, a banana and a handful of almonds (30 g, or 1 oz) on top bring it to about 1,700.

Signs you're eating too little

Eating less is the point. These are the signs you've gone past it:

• You're flat and tired most afternoons. See fatigue on a GLP-1.
• You feel light-headed when you stand up. Often a sign you're short of fluid and salt, which is easy to miss when you're eating and drinking less. See electrolytes and hydration.
• You're colder than usual. A big, sustained calorie deficit turns your body's heat down: in a six-month trial, cutting calories by a quarter measurably lowered core body temperature. On its own it doesn't mean much; alongside the others, it suggests the deficit is bigger than it needs to be.
• Your protein target is out of reach most days. Find yours with the protein calculator.
• There's more hair in your brush than usual. Shedding after big weight loss usually starts a few months after the trigger, so it's a late sign rather than an early one. See hair loss on a GLP-1.

The advisory also lists the signs of an actual nutrient deficiency: tiredness beyond what you'd expect, heavy hair loss, flaky or itchy skin, muscle weakness, wounds that heal slowly and unusual bruising. Those deserve a conversation with your doctor, not just a change of menu.

What to do about it

The fix is rarely more food overall. It's making what you do eat count:

• Protein first at every meal, then vegetables. If you fill up early, what's left on the plate should be the part that mattered least. The protein guide has your numbers.
• Add a small protein snack when a meal falls short. A pot of Greek yogurt, a boiled egg or a glass of milk covers a missed lunch far better than nothing.
• Pick foods that go down easily. The advisory notes that smoothies, protein drinks, soups and cottage cheese are often more appealing than heavier foods like red meat or hard cheese. The protein shakes guide covers how to use them.
• Add energy without adding volume if you're well under your range: nut butter, a drizzle of olive oil over vegetables, milk instead of water in porridge.
• Keep the easiest options for the days after your injection. Eating on injection day covers what tends to work.

When to talk to your prescriber

Tell your prescriber or dietitian if:

• you're struggling to eat or drink at all, or can't keep food down
• you're losing more than about 1 kg (2 lb) a week, week after week. The NHS and CDC suggest 0.5 to 1 kg (1 to 2 lb) a week, very fast weight loss may raise the chance of gallstones, and the advisory links losing 14% or more of your weight within three to four months to significant bone loss
• you have any of the deficiency signs above
• you take insulin or a sulfonylurea, since skipping meals can then cause low blood sugar

The advisory's view is that how far to cut calories should depend on the person, and be adjusted as you go based on how fast you're losing weight and how well you're tolerating it. That makes it a conversation, not a number to push against.

This is general nutrition information, not medical advice. Your doctor or dietitian can set targets that fit your health.