What the first month on a GLP-1 actually looks like
Week by week, from the trial data and the medication labels: what changes, what's normal, what to track, and what belongs in front of your prescriber rather than a search bar.
We build a food tracker. We are not clinicians, and nothing here is advice for your situation — your prescriber owns every decision about your medication. What we can do is lay out what the published trials and the medication labels say about a first month, and be specific about the part we actually know something about: what’s worth writing down while it happens.
Everything with a number attached links to where the number came from.
Week 1: the appetite goes quiet
The first thing most people notice isn’t nausea. It’s silence. Food stops occupying the background of your day.
The trials measured it. Given free access to food, people on semaglutide ate 24% less at 1.0 mg (Blundell et al., 2017) and 35% less at 2.4 mg (Friedrichsen et al., 2021) compared with placebo. That’s not willpower arriving. It’s the medication doing the thing it was approved to do.
Side effects are common and mostly gastrointestinal. From Wegovy’s label, in adults on 2.4 mg versus placebo: nausea 44% vs 16%, diarrhea 30% vs 16%, vomiting 24% vs 6%, constipation 24% vs 11%, abdominal pain 20% vs 10%, fatigue 11% vs 5% (full prescribing information). Worth reading twice: a large minority get through week one with none of it, and nausea is common enough that having it says nothing about whether the medication is working.
Worth tracking this week: what you actually ate, not what you meant to. A week of honest logs is the only way to answer “am I eating enough?” later, and the answer is usually more surprising than people expect.
Week 2: the first weight move, and the noise around it
Weight starts moving, and it moves unevenly. Some of week two’s drop is water and gut contents rather than fat, which is why a single morning reading is close to meaningless this early. A multi-week trend line tells you something; Tuesday does not.
Titration schedules belong to your prescriber, full stop. Escalation timing differs by medication, by person, and by how week one went. If you’re wondering whether to move up, that’s a conversation, not a search.
Worth tracking: weigh at whatever frequency doesn’t make you miserable, and look only at the trend. If the daily number is going to ruin your morning, weigh weekly.
Week 3: protein becomes the thing that matters
This is where the tracking stops being optional, and it’s the part we’d argue about with anyone.
When you lose weight quickly, a meaningful share of what leaves is lean mass. In the evidence summarised by a 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society, 38% of average total weight lost was lean body mass — roughly 10–15% of total loss in women and 20–25% in men.
The same advisory suggests 1.2–1.6 g of protein per kg of body weight per day during active weight reduction, or a flat 80–120 g per day if that’s an easier target to aim at.
Here’s the difficulty nobody warns you about: those targets were written for people with an appetite. On a 900-calorie day, 100 g of protein means protein has to come first at every single meal, before anything else gets room. That is a tracking problem, not a discipline problem, and it’s solvable with a number on a screen.
Worth tracking: protein, specifically, as its own line. Calories take care of themselves on this medication. Protein doesn’t.
Week 4: the check-in, and what to bring to it
Your first proper conversation with your prescriber lands around here, and the difference between a useful one and a vague one is whether you can answer questions with data instead of impressions.
Things you’ll likely be asked, and can only answer from notes:
- How much are you actually eating? A week of logs beats “not much”.
- Which side effects, how often, how bad, and are they fading? Dates matter.
- Any days you couldn’t keep fluids down? That one is a safety question, not a curiosity.
- What does the weight trend look like across four weeks, rather than this morning?
This is the honest case for tracking on a GLP-1, and it’s different from the case for tracking on a diet. You’re not counting to restrict. You’re building a record so that the person making medical decisions is working from something real.
When to contact your prescriber rather than wait
Semaglutide’s label carries warnings for, among others, acute pancreatitis, acute gallbladder disease, acute kidney injury from volume depletion, severe gastrointestinal reactions, hypoglycemia, and heart rate increase (sections 5.2–5.9). Tirzepatide’s label differs in specifics.
We’re not going to publish a symptom checklist and invite you to self-triage against it. Read the label for the medication you were actually prescribed — the link above is the real one, not a summary of a summary — and when something worries you, call. Severe or persistent abdominal pain, and an inability to keep fluids down, are the two that show up in those warnings and are worth acting on rather than sleeping on.
The part people get wrong at week five
Weight loss slows down, for nearly everyone. The internet’s explanation is that the drug stopped working and you need more of it. That isn’t what the evidence says: modelling work from the NIH attributes the plateau to metabolic adaptation and the body’s appetite-regulation circuit reasserting itself against the medication, not to the drug losing potency (Hall, 2024). Tolerance has been documented for the effect on gastric emptying — a different effect from appetite or weight (Jalleh et al., 2025).
Higher doses do produce more weight loss in trials. That’s a dose-response relationship, not a cure for tolerance, and the distinction matters when you’re deciding what to ask for.
If you want the tracking to be less work than this sounds: Macroline logs food by description, barcode, or through Claude, shows a protein floor rather than only a calorie ceiling, and has a body log for the bathroom and symptom side of this that most trackers pretend doesn’t exist. More on that here.
Macroline builds a food tracker. We’re not a medical provider, and this isn’t medical advice for your situation. Talk to the clinician who prescribed your medication.