Gastric sleeve surgery removes roughly 75–80% of the stomach, leaving a narrow tube. The result is that a much smaller volume of food makes you full, and — because the removed portion produces most of the body's ghrelin — you feel considerably less hunger, at least at first.

Both of those change how many calories you take in. What follows is what that usually looks like, and why the numbers move over the first year.

(If you had a gastric bypass rather than a sleeve, the mechanism is different — bypass reroutes the small intestine as well as reducing stomach size, which affects absorption too. Much of what follows still applies, but your program's targets will differ.)

The numbers come from your program, not from a website

Your surgical team sets your calorie and protein targets, and adjusts them based on your starting weight, your labs, your activity, and how your recovery is going. The ranges below are what bariatric programs commonly work with. They're context, not a prescription — and if what your dietitian tells you differs from what you read here, theirs wins.

The first weeks: calories are not the point

Through the liquid and pureed stages, intake is genuinely low — often in the 400 to 800 calorie range — and that is expected. Nobody is counting calories at this stage.

Two things matter instead:

• Fluids. Most programs target 64 oz a day. Dehydration is the single most common reason bariatric patients end up readmitted in the first month.
• Protein. Typically 60 to 80 grams a day. Protein is what preserves lean muscle while you lose weight quickly, and it's the target people miss most often when they can only manage a few ounces at a time.

Hit fluids and protein. The calorie number takes care of itself.

First six months: roughly 800 to 1,200 a day

Once you're on soft and then regular foods, most programs land somewhere in this range — usually three small meals and one or two snacks.

Because the total is low, what's in it matters more than it used to. A pre-surgery diet has room for slack. This one doesn't. Protein comes first at every meal, then vegetables and fruit, then whatever else fits — which usually isn't much.

A practical way to think about the split: if you're around 1,000 calories a day, main meals land near 250 to 300 each and snacks near 100 to 150. But eat to your protein target and your fullness, not to an arithmetic target.

Six to eighteen months: intake climbs

As the stomach settles and you can manage more volume, most people move up — often into the 1,200 to 1,500 range, sometimes higher depending on size and activity. This is normal and expected, not backsliding.

Protein stays where it was. Most programs keep the 60 to 80 gram target indefinitely, and some raise it if you're training seriously.

Maintenance: the part nobody plans for

Eventually weight loss slows and stops, and your intake settles at whatever maintains your new weight. That number is individual, and it's usually higher than people expect — which is its own problem, because appetite tends to return around the same time.

This is the stage where the habits built in the first year decide what happens next. Patients who spent that year learning to eat protein first, eat slowly, and stop when full tend to hold their loss. Patients who spent it waiting to go back to normal tend not to.

A day at roughly 1,000 calories

An illustration, not a plan:

• Breakfast — scrambled eggs with a little cheese, and a few berries
• Snack — Greek yogurt, plain, or a protein shake
• Lunch — canned tuna or salmon with a small amount of light mayo, and soft-cooked vegetables
• Snack — cottage cheese, or a small portion of lean deli meat
• Dinner — three ounces of chicken or fish, half a cup of a soft vegetable, and a small starch if it fits

Note what isn't there: bread as a foundation, large portions of rice or pasta, anything fried, and drinks with meals. Drinking with food fills the stomach with liquid instead of protein, and most programs ask you to stop drinking about 30 minutes before eating and wait about 30 minutes after.

What to do if you're not hitting your targets

Falling short on protein is common and worth raising with your team rather than pushing through. So is the opposite problem — finding you can eat noticeably more than expected, earlier than expected.

Both are things your program has seen many times and can adjust for. Neither is a reason to change your plan on your own.