The Potential Side Effects of GLP-1s

GLP-1 medication works. But it’s not always comfortable, especially early on or after a dose increase.

Common side effects include:
● Nausea
● Fatigue or low energy
● Constipation or digestive changes
● Feeling full very quickly
● Acid reflux or heartburn

Not everyone gets all of these. Some people sail through with barely a wobble. Others have a rough few weeks before things settle.

If you’re in the second group, a few things that help:

Eat smaller, more frequent meals.
Your stomach empties more slowly on GLP-1 medication. Large meals sit heavily. Smaller portions, spread out, are usually easier to tolerate. (More on this in [Meal Timing: Little and Often)

Prioritise protein and veg.
Greasy, heavy, or very rich foods tend to cause more issues. Lean protein paired with vegetables is easier for most people to digest. Save the indulgent stuff for when you’ve adjusted.

Stay hydrated.
Constipation is common, and dehydration makes it worse. Water, fibre, and movement all help keep things moving. (See [Hydration, Fibre, and Electrolytes] for more.)

Watch your electrolytes.
Fatigue and lightheadedness aren’t always about calories. Lower carbohydrate intake, dehydration, or electrolyte imbalance (especially sodium and potassium) can cause them. If you’re feeling dizzy, weak, or “off,” start with food: bananas, potatoes, and salting your meals. For most people, that’s enough. If it’s an ongoing issue, then consider a supplement. But food first.

Don’t force food.
If you genuinely can’t face eating, don’t white-knuckle through a full meal just to hit a target. A protein shake or a few bites of something light beats nothing. And beats making yourself feel worse.

Regular movement.
A short walk after eating can help with digestion and nausea. You don’t need to train hard when you’re feeling rough, but low-impact movement, such as walking, often helps more than sitting still.

Time your meals around training.
If you’re exercising, don’t train on a full stomach. Give yourself a couple of hours after eating, or train fasted if that feels better; experiment and find what works.

Most side effects ease as your body adjusts, usually within a few weeks. They often peak after dose increases, then settle again as your body adapts. If they’re severe or persistent, speak to your prescriber. That’s what they’re there for.

Some people notice changes in other impulses. For some, the urge for alcohol, shopping, or dopamine-seeking behaviours drops. For others, it’s the opposite–a need to replace food-related behaviours with something else. We’ll cover this more in Week 4.

One more thing:
Some people notice a change in their emotional relationship to food – a kind of flatness or disconnection. Meals that used to bring joy might feel neutral. This isn’t universal, and it often settles, but if it’s affecting you, know you’re not imagining it. It’s a recognised experience.

The goal isn’t to suffer through. It’s to find what makes this sustainable for you.

Next: “Energy Levels” Why do a lot of people feel better than expected when they start to eat less, and once the initial adjustment passes?