A coffee in the morning, and nothing else goes down. At lunch, three bites and half the plate goes back. In the evening, the very thought of a steak turns your stomach. On GLP-1 treatment, days often look like this. That is how the medicine works, it calms hunger and slows the emptying of the stomach. The scale goes down. But when you eat little of everything, you also eat too little protein, and your muscle pays.
The treatment, how it is adjusted and how long it lasts, is your doctor's call. Here I am talking about what is on your plate.
You eat a lot less
In a twelve-week trial in 30 people with obesity, one molecule from this family cut the calories eaten freely over the day by 24% compared with a placebo. Participants were less hungry, had fewer cravings, and were less drawn to fatty foods (Blundell et al., 2017). A 2024 review that gathered the studies on what treated people eat found calorie intake down by 16 to 39%. Very few of those studies looked at what was left on the plate (Christensen et al., 2024).
A small American study published this year filled part of the gap. Twenty-eight adults recorded what they ate during the 24 weeks after starting treatment, with no nutrition support at all. Calories went down, and protein with them. About a quarter of the weight lost was muscle, according to an estimate by bioimpedance. And the more protein participants ate, the better their muscle was preserved (Babazadeh et al., 2026). The authors say it themselves, the sample is small and the result still needs confirming. It fits what I see in coaching. The people who eat little protein are the ones who lose the most muscle.
In 2025, four American scientific societies published a joint advisory on nutrition during GLP-1 treatment. Among the challenges, they list deficiencies caused by eating fewer calories, and the loss of muscle and bone. Among the priorities, preserving muscle through strength training and an appropriate diet (Mozaffarian et al., 2025). I covered strength training in the article on GLP-1 and muscle. This one is about protein.
The rule stays the same
At least 30 g of protein in the morning, and at least 30 g after 5 pm. Every day, on treatment or not. For a man, the morning target is more like 40 to 50 g. The evening meal is never optional, even when your appetite is at its lowest. The only exception is a prolonged fasting day.
Those two meals count more than the others. In the morning, the body is coming out of a night spent drawing on its reserves. In the evening, it is about to go many hours without anything. In between, you can follow your hunger.
How you spread protein matters too. In Texas, eight healthy adults ate the same amount of protein for a week, split in two ways. Either about 30 g at each meal, or 11 g at breakfast, 16 g at lunch and 63 g in the evening. With the even split, muscle building over 24 hours was 25% higher (Mamerow et al., 2014). On a GLP-1, the pattern that settles in on its own looks exactly like the second one. Nothing in the morning, almost nothing at lunch, and one real meal at night.
Over the day, aim for about 1.5 g of protein per kilo. If you have a lot of weight to lose, do the maths from the weight you are aiming for, not your current weight.
Protein first
When your stomach fills up after a few bites, the order of your plate decides what gets in. Start with the meat, fish or eggs. Vegetables and carbohydrates come next, if there is room. That order has another advantage, it raises blood sugar less, as I explain in the article on food order.
Eat your protein in one go. A shake sipped over two hours does not raise amino acids in the blood enough to switch on muscle building. On a GLP-1, though, that is what many people end up doing.
Dense foods, not big portions
The aim is not to eat more volume. You need foods that fit a lot of protein into a small space.
Skyr is the best example. About 10 g of protein per 100 g, for 60 calories, twice the protein of Greek yoghurt. A 200 g pot already gives you 20 g. Skyr, yoghurt or kefir, choose them plain, with as few ingredients as possible.
Eggs count for less than people think. Two eggs give about 12 g of protein, and you need four or five to reach 30 g. Three eggs with 200 g of cottage cheese come to about 40 g, if you tolerate dairy well. That is the kind of breakfast that lets a man reach his 40 to 50 g without forcing it.
For meat, poultry or fish, 130 to 150 g gives around 30 g. If that is too much, 80 g of salmon with two eggs adds up to the same. Hard cheese gives as much protein as meat in a very small volume, 25 to 30 g per 100 g, but a lot of calories too. Keep it as a top-up.
On mornings when nothing goes down, an unflavoured protein powder can complete a breakfast that is too light. It completes a meal, it does not replace one. A whey protein shake blended with Greek yoghurt and red berries makes a breakfast of about 40 g that you can drink in a few minutes.
For the really hard days, essential amino acid supplements let you enrich a small meal without eating more. Two eggs with a serving of essential amino acids trigger the same muscle response as a 30 g meal. Talk to your doctor before adding a supplement.
What your doctor needs to know
If even 30 g in the morning feels impossible, or nausea makes you skip whole meals several days running, tell your doctor. It is information they need to adjust your care.
The medicine lowers the volume of what you eat. What you put in that volume is your choice. Your muscle is counting on those two meals, morning and evening.
This article is for information only and does not replace medical advice.