GLP-1 medicines can make losing weight easier by reducing hunger, helping you feel fuller after eating and slowing digestion. Medicines such as semaglutide and tirzepatide can therefore help people eat less without feeling as hungry as they might without treatment.

But how much weight can you expect to lose? It varies from person to person. In the STEP 1 clinical trial, people taking semaglutide 2.4 mg lost an average of 14.9% of their starting body weight over 68 weeks. In the SURMOUNT-1 trial, people taking the highest dose of tirzepatide lost an average of 20.9% over 72 weeks. These are trial averages, not a guarantee of what one person will lose.

Some people will lose less, even when they are taking their medicine as prescribed and making healthy changes. Research has found that genetic differences can affect how people respond to GLP-1 medicines. Your metabolism, health, other medicines and everyday habits can also play a role.

So, if the scales have stopped moving, it does not automatically mean something is wrong with your medication. Sometimes a few easy-to-miss habits are getting in the way.

Why am I not losing weight on GLP-1s?

GLP-1 medicines do not produce the same results for everyone. Individual metabolic and genetic differences can affect how your body responds. Everyday habits can also slow progress, including high-calorie drinks, too little protein, limited strength exercise, low fibre intake, poor hydration, emotional eating and gradually increasing portions.

Hidden Habits That Can Slow Weight Loss On GLP-1s

Some habits are particularly easy to overlook because they may not feel like they are having much impact. Here are a few worth checking.

1. Drinking high-calorie liquids

It is easy to forget about drinks when thinking about what you eat.

A large flavoured coffee, fruit juice, sugary cold drink or creamy smoothie can contain plenty of calories without making you feel as though you have eaten much. You can drink it in a few minutes and still feel ready for your next meal.

Alcohol is another one to watch. Apart from providing calories, it can make some people more likely to snack or choose richer foods. It can also interfere with sleep, and poor sleep can affect appetite and food choices the following day.

This does not mean you need to give up every drink you enjoy. It is more useful to look at what you drink most days. If high-calorie drinks have become part of your routine, they may be adding more to your daily intake than you realise.

Water, unsweetened tea and other low-calorie drinks can help keep hydration up without adding much energy to your daily intake.

2. Not Getting Enough Protein

A smaller appetite can be helpful when you are trying to reduce your food intake, but it can also make it harder to get enough protein.

Protein helps support muscle and other tissues in the body. During fat loss, some muscle can be lost along with body fat. Eating enough protein and doing resistance exercise can help protect muscle during this process.

Good protein choices include eggs, fish, chicken, lean meat, Greek yoghurt, cottage cheese, beans, lentils and tofu.

You do not need to turn every meal into a high-protein meal. Simply making sure that your main meals contain a reliable source of protein can be a useful habit.

If your appetite has become so low that eating enough food feels difficult, speak with your healthcare professional. Eating as little as possible is not the goal of GLP-1 treatment.

3. Skipping Strength Training

Walking is a great form of movement, but it does not provide the same stimulus to your muscles as resistance exercise.

Strength training tells your body that it needs to keep using its muscles. This can be done with weights, resistance bands or your own body. Simple exercises such as squats, lunges, wall push-ups and resistance-band movements can form part of a routine.

Keeping muscle during fat loss is useful for more than appearance. Muscle tissue uses energy, so losing a lot of muscle can reduce the amount of energy your body uses throughout the day.

You do not need to train like an athlete. Two or three resistance sessions each week may be enough to form a useful part of your routine, depending on your fitness level and health.

4. Letting Fibre Slip

Eating less can sometimes mean eating less of everything, including fibre.

Fibre is found in foods such as vegetables, fruit, beans, lentils, oats, wholegrains, nuts and seeds. It supports normal bowel function and feeds helpful bacteria in your gut.

Adults generally need around 22 to 34 grams of fibre a day, although your own needs depend on factors such as age and sex. Increasing fibre gradually and drinking enough fluid can help your digestive system cope with the change.

This needs a little more attention when you are taking a GLP-1 medicine because these medicines can slow digestion. Some people experience constipation as a result.

If you are struggling with ongoing constipation or other digestive problems, speak with your healthcare professional rather than simply adding more fibre.

5. Forgetting About Fluids

When appetite falls, your overall intake may drop without you realising it. That can include fluids.

Not drinking enough can contribute to constipation and leave you feeling tired or unwell. Keeping a water bottle nearby can make drinking regularly easier, particularly if you tend to get busy during the day.

Your fluid needs are not identical to someone else’s. Weather, exercise, diet and health conditions can all affect how much you need.

6. Assuming the Medicine Will Fix Emotional Eating

Physical hunger and emotional eating are not the same thing.

You can feel satisfied after a meal and still want something sweet after a stressful day. You might snack while watching television because it has become part of your evening routine. You may also eat when you are tired, bored or upset rather than because your body needs food.

GLP-1 medicines can help reduce physical hunger, but they do not automatically remove these habits.

This is where paying attention to why you are eating can be useful. If you notice that certain situations repeatedly lead to snacking, you can start looking for another response that feels realistic for your routine.

Support from a health coach can also help here, particularly when eating habits are connected to stress, routines or changes in appetite.

7. Letting Portions Slowly Creep Up

A reduced appetite can make smaller portions feel natural at first. Over time, you may find yourself serving a little more, adding an extra snack or going back for seconds.

Small changes are easy to miss when they happen gradually.

You do not need to measure every bite of food. Instead, pay attention to what your usual portions look like now compared with when you started treatment.

Eating slowly can also give your body more time to register fullness. If you are already feeling satisfied, you do not need to finish a portion simply because it is still on the plate.

A slower result does not always mean the medicine has failed

It is easy to compare your results with someone else’s. Clinical trials, social media and personal stories can create the impression that everyone should respond in exactly the same way.

Research does not show that.

The 2026 Nature study found substantial variation in GLP-1 medication response. Its findings also suggest that genetics contribute to some of this variation, although non-genetic factors explained more of the differences in the researchers’ model.

Your response can also be influenced by the medicine being used, the dose, how long you have been taking it, other health conditions and everyday habits.

Find Out More About GLP-1 Support With Zapmed

GLP-1 treatment is not simply about taking a medicine and hoping for a particular result. Having medical guidance alongside support with food and everyday habits can make the process easier to manage.

At Zapmed, online doctor consultations provide medical oversight for people considering or using GLP-1 treatment. Our health coach support can also provide ongoing guidance around nutrition, appetite changes, eating habits and the practical side of making healthier choices.

Our health coach is a registered dietitian who can provide personalised support and regular WhatsApp check-ins as part of your care. You can learn more about the support available through the Zapmed health coach page and explore the wider range of services on the Zapmed website.

Medical disclaimer

This article is for informational purposes only and should not be construed as medical advice. GLP-1 medicines are prescription treatments and are not suitable for everyone. Speak with a qualified healthcare professional about your individual health needs, medication and treatment plan.