Weight loss doesn't come with a one-size-fits-all solution, and lifestyle modifications alone may not be sufficient for everyone. That is where prescription options like Glucagon-like peptide-1 (GLP-1) receptor agonists come in.

Under professional medical guidance, GLP-1 medications can be prescribed as tools to help with weight management, but they are not risk-free. Studies suggest that GLP-1 users lose a considerable amount of lean mass, and are more likely to underconsume many key nutrients that are important for long term health. When it comes to both health and weight, GLP-1 medications work best when combined with healthy eating and lifestyle changes, and understanding how these medications work and how they affect your nutrition is key to getting the best results.

How these medications work

Some of these drugs were created for diabetes, while others were made specifically for weight loss - that’s why you might see the same drug (eg. semaglutide) marketed under different brand names. No matter what the target is, these medications work by mimicking a natural hormone your body makes called GLP-1. This hormone helps your body control hunger, feel fuller faster, manage blood sugar levels after eating, and slow down digestion. Studies show these medications can reduce how much you eat by 16-39%. 

A few of these medications also work on an additional pathway—the glucose-dependent insulinotropic polypeptide receptor (GIPR)—targeting two pathways at once. This dual action enhances blood sugar regulation and hunger control, often leading to even more effective weight loss.

Regardless of the reason you’ve been prescribed a GLP-1 medication, these medications make it easier to eat less—but the quality of your food still matters, and you're still in control of what you eat and how you move.

Your body will change

When you start taking these medications, many people notice changes pretty quickly. You might feel less hungry, get full faster, and have fewer food cravings. At the same time, you may experience some digestive side effects like nausea, constipation, or stomach discomfort, especially when you first start or when your dose increases. When these things start to happen, paying attention to nutrition becomes really important.

Protein is your friend

Since you'll likely be eating much less, every meal needs to count. Protein is especially important because it helps protect your muscle mass while you lose weight. Studies show that eating enough protein can reduce the risk of losing muscle while you lose fat. 

Protein also keeps you satisfied longer, keeps your metabolism going, and can help stop cravings. Prioritizing protein at each meal is a good start. Good choices include chicken, fish, eggs, Greek yogurt, beans, nuts, and tofu. A registered dietitian can help you determine the exact amount your body needs. 

Add fibre slowly

Fibre may help with digestive side effects, but it’s important to increase your intake slowly. Because GLP-1 medications already slow down digestion, jumping straight to a high-fibre diet can make some GI symptoms like constipation, nausea or bloating worse. Gradually incorporating more fibre, water, and movement, can help manage side effects, but not all fibres are created equally. Certain types of fibre might help with some symptoms while they might make others worse. If you are experiencing gastrointestinal side effects and wondering if a specific fibre strategy might be helpful, speak with a dietitian for personalized guidance. 

Adding fibre-rich foods like vegetables, fruits, whole grains, and legumes to your diet gradually over several weeks is generally recommended to support digestion. 

Nutrients matter

Weight isn’t the only thing to monitor if you’re on a GLP-1 medication. It’s important to make sure you’re getting enough nutrients to stay healthy, which means that what you choose to eat can matter even more. If food intake decreases, it becomes vital to build nutrient-dense meals. A healthcare provider or dietitian can help determine if you have any micronutrient gaps.

Medication isn't the whole story

People who combine medication with good nutrition and regular movement get the best results. The medication makes eating less easier—less hunger might mean easier choices— but you’re the one choosing what to eat and how to move, which matters when it comes to long-term health.

As I tell patients: "Nutrition and exercise are the foundation of your health. For some, medication is an optional tool—like scaffolding—that may help build that foundation more effectively, but the foundation is what ultimately can support you for a lifetime.”

Try it at home

A simple way to include both types of fibre is with oats. This blueberry crumble overnight oats recipe combines oats, chia seeds and fruit—providing a balanced, fibre-rich start to your day. Top with berries, nuts or granola for added texture.

Written by Sarah Casciato, RD