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Guide

GLP-1 side effects: what to eat for each one

Every side effect pushes you towards the same low-protein foods, and a fortnight of that is what starts a strength test falling. Here is the food answer for each symptom, and the signs that need a doctor instead.

The short answer

Almost every GLP-1 side effect pushes you towards the same foods: dry toast, crackers, soup, tea. All of them are low in protein, and a fortnight of eating that way is the commonest reason a strength test starts to fall. This page gives the food answer for each symptom, in a way that still gets protein in. Symptoms that are severe, or that do not settle, belong with your prescriber.

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Nausea

The most commonly reported effect on every medication in this class, and usually worst in the days after a dose step or a weekly injection. Cold, dry and plain beats hot, wet and rich. Prawns, hard-boiled eggs, tinned tuna, plain Greek yoghurt, a thin shake mixed with water rather than milk. Eat small and often rather than waiting for a meal you can face, keep fat low because it sits longest, and take fluid between meals rather than with them.

Ginger and peppermint help some people and are worth trying. What we would avoid is spending a week on crackers, because that is 10 g of protein a day. See nausea, what to eat for the two-day plan.

Constipation

Very common, and mostly the result of eating far less: less food, less fibre and less fluid arriving. The fix is all three together, because fibre without fluid makes it worse. Around 25 to 30 g of fibre a day and 2 litres (68 fl oz) of water. Kiwifruit, pears, oats, chia, linseed and beans are the useful ones; two kiwifruit a day has a decent evidence base behind it.

Protein-wise, keep the tinned fish and the yoghurt, since neither adds to the problem, and go carefully on protein bars, which often carry sugar alcohols that make wind worse. Ask your pharmacist before starting a laxative. See constipation on a GLP-1.

Reflux, burping and sulphur burps

Food sitting in a stomach that is emptying slowly. Fat leaves last, so a creamy or fried meal is the usual trigger, and lying down within three hours turns it into heartburn. Smaller plates, lower fat, four small meals instead of two large ones, no fizzy drinks, and the head of the bed raised 10 to 15 cm (4 to 6 in).

Grilled rather than fried, tomato-based rather than creamy, lean cuts rather than fatty ones. Reflux most nights, trouble swallowing or food sticking needs assessing rather than managing. See reflux and burping.

Fatigue and low energy

Four common causes, in the order worth checking: not enough total food, not enough protein, low iron or another deficiency, and low fluid and sodium. The first two you can test in a week. Put a carbohydrate serve back around your strength sessions, since very low carbohydrate on very low calories is the recipe for feeling wrung out, and salt your food normally.

If the tiredness arrives with a falling strength test, treat it as muscle until proved otherwise. If it comes with hair shedding, feeling cold or dry skin, ask your prescriber for thyroid and iron bloods. See fatigue and low energy.

Muscle cramps

Usually fluid and minerals rather than the medication itself. Eating half as much means half the sodium, potassium and magnesium arriving, and most people also drink less because food carries a surprising amount of daily fluid. Water to about 2 litres (68 fl oz), salt on the food unless your prescriber has told you otherwise, and potassium and magnesium from food: potato with skin, banana, kiwifruit, yoghurt, beans, spinach, almonds, pumpkin seeds.

Cramps that keep coming after a fortnight of that, or that arrive with numbness, weakness or dark urine, need your prescriber the same day in the case of the latter. See muscle cramps.

Diarrhoea and loose stools

More common on tirzepatide than semaglutide in the people we coach. Reduce the fibre load temporarily rather than the protein: rinse tinned legumes, drop the bran, keep the eggs, fish, chicken and dairy if you tolerate them. Replace fluid and salt deliberately, because a few days of this empties the tank faster than low intake alone.

Frequent or persistent diarrhoea, blood in the stool, or an inability to keep fluids down is a prescriber call rather than a dietary adjustment.

Hair shedding

Usually begins two to four months in, and usually follows rapid weight loss and low protein together rather than the medication directly. Protein to at least the floor, and ask your prescriber about iron studies, ferritin, thyroid function and vitamin D, all of which produce the same picture in women over 45. Most shedding of this kind recovers once intake steadies. See hair shedding.

Feeling cold

Partly eating far less, so less heat from digestion. Partly losing the fat layer that insulated you. And partly, in some people, losing muscle, which is the tissue that generates most of your resting heat. The first two are expected. The third is the one to check with a strength test. Warm protein helps twice: soup with chicken, porridge with milk and powder, warm milk with cocoa. See feeling cold.

Sleep that will not settle

Broken sleep usually traces to one of three things you can change. Eating so little during the day that you wake underfed at 3am. A late meal still sitting in a slow stomach when you lie down. Or caffeine and alcohol on top of both. Move the last real meal three hours before bed, make it a 30 to 40 g protein serve, and if you need something later make it dairy, which sits lighter than a cooked meal and still counts.

Sleep is not a soft extra here. Short sleep in a calorie deficit shifts more of the loss towards lean tissue and wrecks the quality of your two strength sessions. Snoring, gasping or heavy daytime sleepiness is a prescriber conversation. See sleep problems on a GLP-1.

Dose step weeks

Every medication in this class is stepped up over time, and each step usually brings a few harder days before things settle. Treat a step week as a planned event rather than a setback: lower your ambitions for whole-food meals, keep a shake and a yoghurt as the floor, keep both strength sessions even if you shorten them, and expect it to ease within one to three weeks. See dose increase week.

The thread running through all of it

Every symptom above has the same side effect: protein falls. Nausea removes meat, constipation removes legumes, reflux removes anything rich, fatigue removes cooking, cramps remove training. Two or three weeks of that is what turns a side effect into a body composition problem, and it is why we ask people to track a seven-day protein average rather than judging themselves on how they feel.

The floor is 1.2 g per kg of goal body weight (0.55 g per lb), whatever else is happening. There is a second cost to a fortnight of dry toast that is worth raising at your next appointment. {claim_with_cite('micronutrient_panel')} On the worst weeks your food might be a shake, a yoghurt and a tin of fish, and that is a perfectly good week. Work out your number with the calculator, and see protein on a GLP-1 for how to hold it when everything is working against you.

When to stop reading and call someone

  • Severe stomach pain Particularly pain that goes through to your back, with or without vomiting. Seek medical care rather than waiting.
  • Vomiting that will not stop Or an inability to keep fluids down for more than a day.
  • Signs of dehydration Dizziness on standing, very little urine, confusion.
  • Chest pain or breathlessness Urgent medical attention, not a dietary question.
  • Anything that frightens you Including symptoms not on this list. Your prescriber would rather hear from you early.

Never change or skip a dose to manage a side effect. That decision belongs to the person who prescribed it, and it is one they make often and willingly when you tell them what is happening.

Free, one page

Forty foods, ranked by protein per bite

The hard part is not knowing you need protein, it is hitting the number on a day when food is the last thing you want. One page, grams and ounces, what a real serve looks like, and the first-bite rule for when appetite is gone. Print it and put it on the fridge.

Then five short emails over five days on keeping muscle while the weight comes off, and a short note every fortnight after that if you want it. One click to stop, any time.

Sent. Check your inbox in the next minute or two, and look in junk if it is not there.

Questions people ask

What should I eat when a GLP-1 makes me feel sick?

Cold, dry and plain, in small amounts: prawns, boiled eggs, tinned tuna, plain Greek yoghurt, a thin shake mixed with water. Keep fat low, eat little and often, and take fluid between meals rather than with them.

How do I fix constipation on a GLP-1?

Fibre and fluid together, around 25 to 30 g of fibre and 2 litres (68 fl oz) of water a day, plus movement. Kiwifruit, oats, chia, linseed and beans. Ask your pharmacist before starting a laxative.

Do side effects mean the dose is too high?

Only your prescriber can judge that, and they will want to know what you are experiencing. Never skip or change a dose yourself to manage a symptom.

How long do GLP-1 side effects last?

Most settle within one to three weeks of starting or stepping up. Symptoms that persist beyond that, or that are severe at any point, should be reviewed rather than endured.

Why do side effects cost me muscle?

Because every one of them pushes you towards low-protein food and away from training. Two or three weeks of toast and tea is what turns a temporary symptom into a falling strength test.

The two things to hold on to through a bad fortnight

Side effects are a prescriber conversation. What they cost you in food is ours, and it comes down to a floor and a short list of markers.

Guideline-informed protein targets during this kind of weight loss start at 1.2 g per kg of body weight a day (0.55 g per lb). Arslan S, Clinical Nutrition ESPEN 2026

Vitamin D, B12, iron studies, folate, zinc and thiamine are the markers this literature suggests watching. Ask your prescriber whether they are worth checking for you; we do not order or interpret bloods. Arslan S, Clinical Nutrition ESPEN 2026

The papers these numbers come from

  • Arslan S. Medical nutrition in the glucagon-like peptide-1 (GLP-1) era: Protein strategies, micronutrient monitoring, and lean mass preservation. Clinical Nutrition ESPEN, 2026. Narrative review, guideline-informed targets. doi:10.1016/j.clnesp.2026.103305

Last reviewed 18 September 2026. We update these figures when a larger or better study replaces them, and we say what changed. How we handle evidence.

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Every guide, by medication and situation

EverStrong provides nutrition and strength coaching and education. It is not medical advice and does not replace your prescribing doctor. Consult your doctor before starting a new exercise or nutrition plan, especially with a heart, kidney, liver or metabolic condition, if pregnant, or with a history of disordered eating.