Your doctor has started one of the injectable medicines as part of your weight treatment. After the first weeks your appetite has dropped noticeably, you cannot finish half your plate and the scales are going down. At this point most people think: “I’m eating so little anyway, what I eat no longer matters.” In reality the opposite is true. When you eat less, the content of each meal becomes more valuable.
This page is not a promotion of any medicine; decisions about starting, dosing and stopping medication belong to the doctor alone. Here we explain, for people using this treatment on medical advice, what nutrition during weight-loss injections should look like, how to prevent muscle loss, what to watch for with side effects and how to prepare for the period after the medication.
What are weight-loss injections and how do they work?
The medicines commonly known as weight-loss injections are prescription medicines that mimic the effect of GLP-1, a hormone released from the gut after eating. Semaglutide, liraglutide and tirzepatide are the known active substances in this group. They act in three main ways: they send a fullness signal to the appetite centre in the brain, slow the emptying of the stomach and contribute to blood sugar regulation. As a result, the person gets less hungry, feels full sooner and has fewer constant thoughts about food.
These medicines are prescribed by a doctor for people who meet certain criteria in the treatment of type 2 diabetes and obesity, and are used under medical supervision. They are not suitable for everyone who wants to lose a few kilos; there are situations in which they cannot be used, and their side effects can be serious.
What is the dietitian’s role in this process?
A dietitian does not recommend, start or change the dose of a medicine. The dietitian’s job is to turn the reduced appetite the medicine provides into healthy weight loss. This comes down to four things:
- Meeting protein, vitamin and mineral needs despite the reduced food intake
- Making sure that as much as possible of the weight lost is fat, and preserving muscle mass
- Easing digestive side effects such as nausea, constipation and reflux through diet
- Building lasting eating habits while the medicine is being used
Your doctor’s check-ups continue throughout; the nutrition plan is prepared in line with the doctor’s treatment.
Why does nutrition matter so much while using injections?
Eating little and eating well are not the same thing. When appetite shuts down, people tend to go for what is easy: a couple of crackers, some fruit, a glass of tea. Energy intake falls and the scales go down; but the protein the body needs is not taken in either. In that case the body meets its needs from its own muscle.
In rapid weight loss, part of the weight lost is always muscle; if nutrition is inadequate, that share grows. Muscle loss is not only a matter of strength and appearance. It reduces the energy used at rest, increases tiredness and makes it easier to regain weight when the medicine is stopped. Other consequences of inadequate nutrition include hair loss, weakness, dizziness, constipation and vitamin and mineral deficiencies.
How should you eat while using weight-loss injections?
Start the plate with protein
Because your stomach fills quickly, the order on the plate becomes important. Eat the protein source first: eggs, yoghurt, cheese, fish, chicken, meat or pulses. Then move on to the vegetables, and lastly the bread, rice or pasta. If you cannot get enough protein at main meals, small but dense snacks such as strained yoghurt, kefir, curd cheese or a boiled egg are planned. Your daily protein requirement is calculated individually according to your weight, age and kidney health.
Small, regular meals
Large portions increase stomach fullness and nausea in this period. Dividing the day into three small main meals and one or two snacks is better tolerated. Skipping meals because you are not hungry widens the nutrient gap by the end of the day; eating by the clock is a method that works at this stage.
The nutritional value of every mouthful
Because the amount you can eat is limited, there is no room for foods that fill the stomach but have little nutritional value. Priority goes to eggs, yoghurt, fish, vegetable dishes cooked with olive oil, pulses, nuts and fruit rather than sugary drinks, pastries and packaged snacks.
Fibre and vegetables
Fibre is important in preventing constipation, a common side effect of these medicines. However, because stomach emptying is slowed, very large salad portions can cause bloating. Cooked vegetables, soups, oats and flaxseed are generally better tolerated; the amount is increased gradually.
Fluid intake
Thirst can decrease along with appetite. Too little fluid increases constipation, headache and weakness. Spreading water through the day instead of drinking a lot at once with meals reduces stomach fullness.
What to limit
Fatty and fried foods, very sugary foods and alcohol tend to increase nausea and reflux. Alcohol is also a source of empty energy at a time when little is being eaten.
Dietary advice for side effects
Side effects involving the digestive system are common, especially at the start of treatment and when the dose is increased. The advice below is for mild complaints; tell your doctor about severe or persistent symptoms.
Nausea
Eat small portions slowly and stop as soon as you feel full. Avoid fatty, strong-smelling and very spicy foods. Do not lie down straight after eating. Dry and plain foods and soft options such as yoghurt, boiled potatoes and soup are generally better tolerated.
Constipation
Increase your fluid intake, move every day, and add cooked vegetables, oats, dried apricots or prunes and flaxseed to your meals. If you have not been able to go for several days or have abdominal pain as well, consult your doctor. For general advice, see the nutrition for digestive and gut health page.
Reflux, belching and bloating
Bring your evening meal forward, do not eat in the two to three hours before bed, stay away from fizzy drinks and make portions smaller.
Diarrhoea
Replacing lost fluid and minerals is the priority. Fatty foods, products containing sugar alcohols and large amounts of raw fruit and vegetables are reduced temporarily.
Preventing muscle loss: protein and resistance exercise
There are two conditions for preserving muscle mass, and neither replaces the other: enough protein and regularly working the muscles. Resistance exercise two or three days a week, that is, movements done with weights, resistance bands or body weight, tells the body that muscle needs to be kept. Walking is valuable for cardiovascular health, but on its own it is not enough to prevent muscle loss. If you are new to exercise, get your doctor’s approval and start with a light programme.
Follow-up looks not only at the scales but also at the fat and muscle proportions in body composition analysis. If muscle mass is falling markedly while the scales drop quickly, the plan is reviewed.
Why does appetite come back when the medicine is stopped?
These medicines are effective for as long as they are used. When they are stopped, the fullness signal returns to its level before the medicine; appetite and thoughts of food come back. Research shows that a considerable part of the weight lost can be regained after treatment ends. This is not a weakness of will but the expected result of the medicine’s effect wearing off.
For this reason, the period in which the medicine is used should be treated as an opportunity to build habits: regular meals, a protein-based plate, movement, sleep and work on emotional eating. Putting these in place while appetite is suppressed is much easier than doing so afterwards. Your doctor decides when and how the medicine will be stopped; more frequent nutrition follow-up is recommended in this period. To work on your relationship with food, see the eating behaviour and emotional eating page.
Common mistakes made by people using weight-loss injections
- Skipping meals because they are not hungry: It is almost impossible to meet protein and nutrient needs with one meal a day.
- Getting through the day on tea, coffee and a few snacks: The scales go down, but most of what is lost is muscle.
- Putting off exercise until “after I’ve lost weight”: Muscle loss is greatest when weight is falling fast.
- Hiding side effects from the doctor: Complaints that could be resolved with a dose adjustment or an additional measure are endured unnecessarily.
- Using products without a prescription, from the internet or from an unknown source: Counterfeit products and those not stored under proper conditions carry a serious health risk.
- Stopping the medicine on their own on reaching the target weight: Stopping should be planned with the doctor.
- Seeing the medicine as the whole solution: Results do not last unless diet and activity habits are established.
When should you see a doctor?
In the following situations, contact your doctor or the emergency department without waiting:
- Severe abdominal pain that does not pass or that spreads to the back
- Repeated vomiting, being unable to keep fluids down, marked weakness and dizziness
- Pain in the upper right abdomen, yellowing of the skin or eyes
- In people taking diabetes medication, signs of low blood sugar such as trembling, sweating and confusion
- Planning a pregnancy or suspecting you are pregnant
Frequently asked questions
Do I need to diet as well while using injections?
A restrictive diet is not needed; appetite is already reduced. What is needed is planned eating that makes sure the smaller amount contains enough protein and nutrients.
My hair has started to fall out. Could it be related to my diet?
Rapid weight loss and too little protein, iron or zinc can increase hair loss. Your diet should be reviewed along with any tests your doctor considers necessary.
Will I regain the weight when I stop the injections?
There is a risk of gaining weight when appetite returns. The way to reduce that risk is to build lasting habits while using the medicine, preserve muscle mass and continue follow-up after stopping.
Can a dietitian prescribe weight-loss injections?
No. These medicines are prescribed only by a doctor. The dietitian prepares and monitors the nutrition plan during the period in which the medicine is used.
I have no appetite at all. Do I still have to eat?
Yes. The body’s need for protein, vitamins and minerals does not depend on appetite. Small portions eaten at set times and with high nutritional value are the basis of this period.
