Saxenda Works by Mimicking a Hormone That Tells Your Brain You're Full

That's the short answer. Saxenda (Liraglutide) is a GLP-1 receptor agonist — a medication that copies the effects of a natural hormone in your body called GLP-1. By activating the same receptors that GLP-1 targets, Saxenda reduces hunger, helps you eat less, and supports weight loss.

But what does that actually mean inside your body? Let's break it down in plain language.

What GLP-1 Is and Why It Matters

GLP-1 stands for glucagon-like peptide-1. It's a hormone produced in your small intestine after you eat. When food enters your gut, GLP-1 is released and does several important things:

• Signals your brain that you've eaten. GLP-1 travels to areas of the brain that regulate appetite, particularly the hypothalamus. It activates receptors there that create a feeling of fullness and satisfaction.
• Slows down your stomach. GLP-1 slows gastric emptying — the rate at which food leaves your stomach and enters your intestines. This means food stays in your stomach longer, keeping you feeling full for a longer time after eating.
• Helps regulate blood sugar. GLP-1 stimulates insulin release and suppresses glucagon (a hormone that raises blood sugar), which helps keep blood sugar levels stable after meals.

The problem? Natural GLP-1 is broken down by your body very quickly — within minutes. Its effects are short-lived.

How Saxenda Mimics GLP-1

Saxenda's active ingredient, Liraglutide, is a modified version of human GLP-1. Scientists tweaked the molecular structure so that it resists the enzyme (DPP-4) that normally breaks down GLP-1. The result is a medication that activates the same receptors as natural GLP-1, but lasts much longer — about 13 hours in your body, compared to just a few minutes for the natural hormone.

This is why Saxenda is injected once daily. Each injection provides a sustained level of GLP-1 receptor activation throughout a large portion of the day.

What Happens When You Take Saxenda

Here's a step-by-step look at what happens in your body after you inject Saxenda:

1. Liraglutide enters your bloodstream. After subcutaneous injection, the medication is absorbed into your blood over several hours.
2. It reaches GLP-1 receptors in your brain. Liraglutide binds to receptors in the hypothalamus and other brain regions that control appetite and food intake.
3. Your appetite decreases. With GLP-1 receptors activated, you feel less hungry and more satisfied with smaller portions of food.
4. Your stomach empties more slowly. Food stays in your stomach longer, which extends the feeling of fullness after meals.
5. You eat fewer calories. The combined effect of reduced appetite and prolonged fullness leads to lower calorie intake — without requiring constant willpower.
6. Weight loss follows. Over weeks and months, the consistent reduction in calorie intake results in gradual, steady weight loss.

How Long Does Saxenda Take to Work?

Most people start noticing reduced appetite within the first week or two of treatment, even at the starting dose of 0.6 mg. However, meaningful weight loss takes longer.

In clinical trials, patients typically saw:

• Noticeable appetite changes: Within 1-2 weeks
• Early weight loss: Within the first 4-8 weeks
• Significant weight loss: By 12-16 weeks at the full 3.0 mg dose

Your doctor will usually evaluate your progress at 16 weeks. If you haven't lost at least 4% of your body weight by that point, they may discuss whether to continue or try a different approach.

Keep in mind that the five-week dose escalation means you won't reach the full dose until week 5. This gradual ramp-up is designed to reduce side effects, especially nausea.

How Long Do Saxenda's Effects Last?

Each dose of Saxenda provides appetite-suppressing effects for most of the day. Liraglutide has a half-life of about 13 hours, meaning it stays active in your system for a good portion of each 24-hour period.

However, Saxenda's effects depend on continued use. If you stop taking it, the medication clears your system within a few days and your appetite will return to its pre-treatment level. This is why Saxenda is designed for long-term use as part of an ongoing weight management plan that includes diet and exercise.

Some patients experience weight regain after stopping Saxenda. This is normal and reflects the fact that obesity is a chronic condition — similar to how blood pressure rises again when you stop taking blood pressure medication.

How Saxenda Compares to Wegovy and Zepbound

Saxenda isn't the only GLP-1 medication for weight loss. Here's how it stacks up against the newer options:

Saxenda vs. Wegovy

Both are GLP-1 receptor agonists, but they're different medications:

• Active ingredient: Saxenda uses Liraglutide; Wegovy uses Semaglutide.
• Dosing frequency: Saxenda is injected daily; Wegovy is injected once weekly.
• Weight loss: Wegovy shows greater average weight loss in clinical trials — about 15% of body weight compared to 7-8% with Saxenda.
• Availability: Both have experienced supply issues, though Saxenda supply has improved with generic availability.

Saxenda vs. Zepbound

Zepbound (Tirzepatide) is a newer type of medication — a dual GIP/GLP-1 receptor agonist:

• Mechanism: Zepbound targets both GIP and GLP-1 receptors, while Saxenda targets only GLP-1.
• Dosing frequency: Zepbound is injected once weekly; Saxenda is daily.
• Weight loss: Zepbound has shown the greatest average weight loss among approved medications — over 20% of body weight in clinical trials.
• Cost and access: Both are expensive; generic Liraglutide may give Saxenda a cost advantage.

Your doctor can help you decide which medication is best for your situation based on your health history, goals, insurance coverage, and what's available. For a deeper comparison, read our guide to alternatives to Saxenda.

Final Thoughts

Saxenda works by doing what your body already tries to do — signal your brain that you're full. The difference is that Saxenda's effects are stronger and longer-lasting than the natural hormone. Combined with a reduced-calorie diet and exercise, it can be an effective tool for sustained weight loss.

If you and your doctor decide Saxenda is right for you, Medfinder can help you find a pharmacy with it in stock. And if cost is a concern, check out our guide to Saxenda savings programs.