How do weight loss injections work?

Recently, a new generation of weight loss injections has totally changed the way in which people lose weight. These can lead to weight loss of up to 25% in 18 months and can finally provide an end to the fad diets and false promises which have bedevilled people’s weight loss journeys for too long. But how do they work?

In this ever-evolving landscape, weight loss injections  have emerged as a “game-changer”, offering effective and targeted solutions for individuals living with obesity. This blog explores weight loss injections: how they work, the injection process, what to expect from popular drugs like Wegovy, Mounjaro and Saxenda, and why you should always take them as part of a specialist weight management service. 

Understanding how GLP-1 medications work

Medications such as Wegovy, Mounjaro and Saxenda, belong to a class of drugs called GLP-1 receptor agonists. This is because they mimic the action of glucagon-like peptide-1, a natural hormone in the body which manages hunger. Their primary mechanism revolves around suppressing hunger and promoting a sense of fullness, leading to reduced food intake.

At CheqUp, we summarise this as “Feel full. Eat less. Lose weight”

As part of their action, GLP-1 medications slow down the emptying of the stomach, helping individuals to feel satisfied for longer, and they act on the brain to dampen cravings and the desire to eat, creating a dual effect that helps weight loss.

How the injections work

The delivery of these medications involves a straightforward yet crucial process – injection. Typically administered via a pre-filled pen device, the injection ensures a controlled and precise dose every time. The pen is designed for self-administration and at-home use making it a convenient option for most people.


The injection process is relatively painless, with the pen delivering the medication just beneath the skin. As can be seen from the image below, the needle is only 3-4 millimetres long, smaller than the length of a drawing pin. 

It’s recommended that weight loss injections are used in the body fat of the stomach or thigh and that people change the injection site frequently to maintain effectiveness and minimise any potential discomfort.

Needle size

What to expect from Wegovy, Mounjaro, and Saxenda

The global clinical trials of these weight loss injections provide the best indication of anticipated weight loss.  A CheqUp doctor  will help you decide the best medication for you and your circumstances.

Let's take a closer look at the expected weight loss outcomes from the three main drugs which come in the form of weight loss injections:

1. Wegovy (Semaglutide)

 Clinical trials, such as the STEP trials, have demonstrated remarkable results, showing weight loss averaging 15% over approximately 15 months. This underscores Wegovy's effectiveness in achieving substantial and sustained weight loss. At least 1 in 3 participants lost 20% of their body weight or more during the clinical trials.

2. Mounjaro (Tirzepatide)

Similar to Wegovy, Mounjaro has exhibited promising weight loss outcomes in clinical trials. The SURMOUNT trials have reported average weight reductions of up to 26% over 18 months positioning it the most effective weight loss medication available.

3. Saxenda (Liraglutide)

Saxenda has been helping people  lose weight for many years and can be considered as the “first generation” of GLP-1 medications. Clinical trials, including the SCALE trials, have shown average weight loss of about 10% over a year.

Navigating side effects

While these weight loss injections have proven to have weight loss benefits, it's essential to be aware of potential side effects. Common side effects may include nausea, vomiting, diarrhoea, and constipation. These effects are often temporary, are usually associated with the dose increase stage (which we’ll discuss next)  and tend to subside as the body adjusts to the medication.

Patients should promptly report any unusual or severe side effects to their healthcare providers. Additionally, clinicians carefully monitor patients for rare but serious complications, such as pancreatitis.

Let’s talk dose titration

It takes time for our bodies to get used to  all GLP-1 medications. To avoid the side-effects becoming unmanageable, we need to start taking the medication in small doses and slowly increase until we are at the top (“maintenance”) dose.

This is called “dose titration” and its exact application varies from drug to drug. For example, with Saxenda (a daily injection of Liraglutide) the dose titration period lasts 5 weeks. Whereas for the weekly injections of Wegovy and Mounjaro the period is five and six months respectively.

The medications have been shown to work most effectively when at their top doses for a period of many months. Even though many people report weight loss with this medication within the first few weeks, this medication should be taken for at least 6 months to achieve real, long lasting results. Unfortunately, there is no quick fix!

Wegovy effectiveness

A long-term investment in your health

GLP-1 medications were not designed to be taken in isolation. Instead, the weight loss achieved in the clinical trials was the result of months of support from doctors, dietitians, physical activity advisors, nurses etc.

That’s why CheqUp provides a full weight management service to our clients. We believe that embarking on a weight loss journey is a serious decision made by people who are committed to losing weight for the long term. It’s worth doing properly.

Weight loss injections have completely revolutionised the weight loss process. For the first time, people can take medication to lose the amount of weight which has historically been associated with bariatric (stomach-altering) surgery. But these weight loss injections should not be taken without the support of a team of experienced specialists.

Take the first step now.

Published: 30 Nov  2023