The guidance that addresses this question directly is a 2024 review in Obesity on nutritional considerations with antiobesity medications, which sets protein above 60 to 75 g a day and up to 1.5 g per kg of body weight, fibre at 21 to 25 g for women and 30 to 38 g for men, and fluid above 2 to 3 litres a day (PMID 38853526).
Those are intake targets rather than a meal plan, and they exist because the problem on these drugs is the opposite of the usual one. Appetite falls sharply, so the question stops being how to eat less and becomes how to fit everything the body needs into a much smaller volume of food.
- Protein: 10% to 35% of energy, more than 60 to 75 g a day, up to 1.5 g per kg of body weight. Eat the protein portion of each meal first.
- Fibre: 21 to 25 g a day for women, 30 to 38 g for men. This is the main lever on the constipation these drugs cause.
- Fluid: more than 2 to 3 litres a day, because reduced appetite reduces drinking as well as eating.
- The foods that reliably worsen nausea and reflux are high-fat, spicy, alcoholic and carbonated. Smaller, more frequent meals and stopping before feeling full do more than any food swap.
The published targets, in one table
Every figure below is from the same review, which drew them from the Dietary Guidelines for Americans and from the bariatric and low-calorie-diet literature where no medication-specific evidence exists.
| What | Target | Why it is on the list |
|---|---|---|
| Protein | 10% to 35% of energy; above 60 to 75 g/day and up to 1.5 g/kg body weight/day | Loss of lean body mass, weakness, oedema, hair and skin changes with inadequate intake |
| Fibre | 21 to 25 g/day for women, 30 to 38 g/day for men | Constipation; also a dietary component of public health concern for the general population |
| Fluid | Above 2 to 3 litres/day, personalised | Dehydration, hypotension, tachycardia; older adults are at greater risk |
| Carbohydrate | 45% to 65% of energy, roughly 135 to 245 g/day at 1200 to 1500 kcal; added sugars under 10% | Severe restriction does not improve long-term results and crowds out micronutrient sources |
| Energy | 1200 to 1500 kcal/day for most women, 1500 to 1800 kcal/day for men | Described as safe intakes during weight reduction |
| Micronutrients | Consider a complete multivitamin, calcium and vitamin D as appropriate | Potassium, calcium and vitamin D are shortfall nutrients; iron and vitamin B12 in specific groups |
The protein figure is the one most often misquoted. It is per kilogram of actual body weight, not of ideal body weight, and 1.5 g/kg is described as the top of the typical range rather than a floor. For context, the reference intake for a healthy adult of normal weight is 0.8 g/kg.
Why composition matters more once you are eating less
Most people do not start from a strong nutritional position. A 2026 analysis of NHANES data covering 16,143 adults found that 43.5% of US adults met the prescribing criteria for these medications, and that this group had measurably poorer diet quality than ineligible adults, with lower scores specifically for fruit, vegetables, whole grains and plant proteins. Inadequate intakes were modestly more common for vitamin C, vitamin A, magnesium, vitamin E, vitamin D, fibre, potassium and vitamin K.
Then total intake falls, which is the point of the drug. The same proportional gaps inside a smaller total become absolute shortfalls, which is why the published guidance is written as nutrient targets rather than as a list of foods to avoid.
Protein first, literally
The most concrete behavioural instruction in the review is about order rather than amount: patients should be instructed to consume high-protein foods first at each meal to ensure adequate protein intake. On a drug that produces early fullness, whatever is on the plate first is what actually gets eaten.
The named food sources are seafood, lean meat, poultry, low-fat dairy, eggs, beans, peas, lentils, nuts, seeds and soy products. Where whole foods do not get there, the review notes that meal-replacement products typically containing 15 to 25 g of protein per serving may be recommended. Why lean mass is the specific concern is covered in muscle loss on a GLP-1.
The foods that reliably make side effects worse
Gastrointestinal effects are the most common adverse events on these drugs, mostly mild to moderate, dose-dependent and transient. The review’s dietary advice for managing them is short and specific: consume smaller and more frequent meals, stop eating before feeling full, and avoid foods and beverages that worsen symptoms, naming high-fat foods, spicy foods, alcohol and carbonated beverages.
Two of those are worth separating out. High fat slows gastric emptying, which is already slowed by the drug, so a high-fat meal compounds the mechanism rather than merely irritating. And alcohol interacts with these medications in more ways than nausea, which is covered in alcohol on a GLP-1. How often nausea is reported by drug and dose, and when it peaks, is in nausea on a GLP-1.
Reflux is common enough to have its own note: the review points out that weight reduction itself often improves reflux symptoms, while short-term acid suppression is a clinical decision rather than a dietary one.
Work out your own intake targets
Our calculator turns a starting weight into the calorie and protein figures this guidance is built on.
Constipation is a fibre and fluid problem
Constipation is the side effect most directly answerable with food. The recommendation is to increase fibre gradually alongside adequate fluid, because fibre without fluid tends to make the problem worse rather than better.
The review is unusually specific about which fibres do what. Soluble, non-fermentable, gel-forming fibres such as psyllium, and insoluble fibres such as coarse wheat bran, increase stool water content and bulk, which aids passage. Fermentable fibres are good for other reasons but are not the ones named for this purpose. A fibre supplement is flagged as reasonable when food alone will not reach the target.
What the trials actually asked participants to do
Worth knowing, because the headline percentages were produced alongside a diet, not instead of one. In STEP 1, every participant in both arms received counselling every four weeks from a dietitian or similar professional, aimed at a 500 kcal a day deficit relative to estimated total energy expenditure, plus 150 minutes a week of physical activity.
That is the background against which 14.9% was measured. The SURMOUNT trials used a comparable structure. None of them tested a specific dietary pattern against another, so there is no trial evidence that one named diet outperforms another on these drugs. What the evidence supports is hitting the nutrient targets inside a reduced intake, which is what the calorie figures behind the trials are built from.
When reduced appetite becomes something to raise
The guidance draws a line between an appetite that has fallen usefully and one that has fallen too far. Individuals with significantly depressed appetite are advised to take fluids and small nutrient-rich meals more frequently, and the review notes that a dose adjustment may be considered when poor appetite is preventing adequate intake of fluids, protein or micronutrients.
That second part is a conversation with the prescriber rather than something to act on alone. The practical signal to raise is persistent inability to drink or to eat protein, rather than simply not feeling hungry, and the review advises contacting a clinician if gastrointestinal symptoms do not settle as expected or get worse.
FAQ
How much protein should you eat on a GLP-1?
The 2024 Obesity review of nutritional considerations with antiobesity medications puts protein at 10% to 35% of energy intake, with more than 60 to 75 g a day and up to 1.5 g per kg of body weight a day described as typical. Above 1.5 g per kg may be considered on an individual basis. The ordinary adult reference intake is 0.8 g per kg.
What foods should you avoid on a GLP-1?
The same review names high-fat foods, spicy foods, alcohol and carbonated beverages as the categories that commonly worsen gastrointestinal symptoms. It pairs that with eating smaller and more frequent meals and stopping before feeling full, rather than with cutting out any particular food group.
How much water should you drink on a GLP-1?
The published recommendation is more than 2 to 3 litres a day, personalised for age, body size, health history and activity. Fluid matters more than usual on these drugs because reduced appetite tends to reduce drinking as well as eating, and because dehydration raises the risk of complications such as acute kidney injury.
How much fibre do you need on a GLP-1?
The adequate intake used in the guidance is 21 to 25 g a day for women and 30 to 38 g a day for men, depending on age. It specifically names gel-forming soluble fibres such as psyllium and insoluble fibres such as coarse wheat bran, which increase stool water content and bulk, as useful for the constipation these drugs commonly cause.
Do you need to cut carbohydrates on a GLP-1?
The guidance says severe carbohydrate restriction is not necessary because it does not produce greater long-term weight reduction and may crowd out fruit, vegetables and whole grains. It keeps carbohydrate at 45% to 65% of energy, which is roughly 135 to 245 g a day on a 1200 to 1500 kcal intake, with added sugars under 10% of energy.
Should you take a multivitamin on a GLP-1?
The review says consideration should be given to recommending a complete multivitamin, calcium and vitamin D as appropriate for patients receiving these medications. It is framed as a clinical judgement rather than a blanket rule, and the nutrients it flags most often are potassium, calcium, vitamin D, iron in women of childbearing age and vitamin B12 in older adults.
Sources
- Almandoz JP, Wadden TA, Tewksbury C, et al. Nutritional considerations with antiobesity medications. Obesity (Silver Spring). 2024;32(9):1613-1631. PMID: 38853526
- Diet Quality and Micronutrient Intake among United States Adults Eligible for GLP-1 Receptor Agonist Antiobesity Medications: A Nationally Representative Analysis. J Nutr. 2026;156(9):101753. PMID: 42520970
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PMID: 33567185
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. PMID: 35658024
This article is for information only and is not medical advice. Dosing, suitability and any change to treatment are decisions for your prescriber.