Eating and supplementing well on GLP-1 medications

The short version

Eat protein first at every meal, aim for roughly 1.2 to 1.6 grams of protein per kilogram of body weight a day, drink more than feels necessary, and keep an eye on iron, B12, vitamin D, magnesium and fibre. Lift something heavy two or three times a week. That is the whole strategy, and it is the same one the 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and the Obesity Society describes in their nutritional priorities paper.

This page is about nutrition while taking a medication. It never says a supplement supports, treats or works with a GLP-1 drug, because that is a claim no honest brand can make and a line we keep.

What the medication actually changes

GLP-1 receptor agonists slow gastric emptying and reduce appetite. Slower emptying is why a normal portion can feel enormous, and reduced appetite is why total intake drops without any conscious decision to eat less. Both effects are the intended mechanism, not a fault.

The nutritional consequence is simple: a smaller plate carries fewer of everything. Protein tends to go first, because it is the part of a meal people finish last. The micronutrients riding along with protein-rich foods go with it.

Protein, the one that matters most

Weight loss is rarely pure fat. A share of what comes off is lean mass, and a higher protein intake paired with resistance training preserves more of it. The 2025 advisory notes targets of 1.2 to 1.6 g per kg a day during active weight reduction, and that using actual body weight can significantly overestimate needs in obesity, giving adjusted body weight as an example basis.

Practical version: eat the protein part of the meal first, when appetite is strongest. Cold protein goes down more easily than hot. A shake is food that has had the water taken out, and it counts.

Our free protein calculator works out your range on the adjusted-weight basis the advisory describes, and shows the working underneath so you can check it.

Fluid, more than you think

The National Academies set a total water Adequate Intake of about 2.7 litres a day for women and 3.7 for men, from drinks and food together, with roughly a fifth coming from food. Eat less food and that fifth shrinks, so more of it has to come from your glass.

This one has teeth. The prescribing information for semaglutide and tirzepatide warns of acute kidney injury in people who became dehydrated through nausea, vomiting or diarrhoea. If you cannot keep fluids down, that is a prescriber call, not a home remedy.

The water calculator adjusts the National Academies figures for how much less you are eating.

Fibre, and the constipation that comes with it

Constipation is one of the most common complaints on these medications, and it follows directly from slowed gut motility plus less food plus less fluid. The order of operations matters: fluid first, fibre second, built up gradually, because a sudden fibre jump without fluid makes things worse.

The Dietary Guidelines scale fibre to energy intake at 14 g per 1,000 calories, which is the useful basis when appetite has shrunk. The fixed comparison is the National Academies Adequate Intake of 25 g for women and 38 g for men up to 50, and 21 and 30 after.

Our fibre calculator gives you both numbers side by side.

Electrolytes when the stomach is unsettled

Nausea and vomiting cost more than water. Sodium, potassium, magnesium and calcium are the four most likely to run low, and their symptoms overlap with ordinary GLP-1 side effects, which makes a blood test the only honest way to tell the difference. Severe cases of electrolyte imbalance have been reported, so persistent vomiting is a medical question.

The nutrients that slip first

The deeper version, with sources, is in the nutrient gaps piece.

Hair, and the frightening bit

Rapid weight loss pushes a large share of hair follicles into their resting phase at once, and they shed together two to four months later. It is called telogen effluvium, it is temporary, and it is the same pattern seen after bariatric surgery, after severe illness and after crash diets. Protein and iron are the two levers. Shedding that starts suddenly, comes with a scalp rash, or leaves smooth bald patches is a different problem and worth an appointment.

We wrote the whole thing up in why am I losing hair on Mounjaro.

Where a supplement fits, and where it does not

Food first, always. A capsule cannot carry protein in any meaningful amount, and nothing in a bottle substitutes for resistance training. What a supplement can do is cover the small nutrients that get thin when portions shrink, in forms that are gentle on a stomach that is already slow.

Keel is the thing we happen to make for that window: digestive enzymes, a spore probiotic, ginger and peppermint, plus methylated B12, folate, B6, iron, zinc, magnesium, biotin, D3 and BioPerine, two capsules a day with food. Every amount is on the label, and the full table is below rather than behind a link.

What this guide is not

It is not medical advice, and it is not weight-loss advice. It does not know your labs, your other medicines or your history. If you are pregnant, nursing, under 18, or managing a medical condition, talk to your prescriber before changing how you eat or adding anything new, ours included.