Weight Loss Jabs: Should They Be Your First Option?
Over the last year, weight loss injections like Wegovy, Ozempic (semaglutide), and Mounjaro (tirzepatide) have exploded in popularity.
You’ve probably seen the headlines.
Maybe you know someone using them.
Maybe you’ve wondered if they’re the shortcut you’ve been looking for.
At Stack House Gym, we’re not here to judge trends — we’re here to look at the facts and help people make informed, long-term decisions about their health.
We have pulled together research to provide a balance view on the use of weight loss injections.
Do Weight Loss Jabs Actually Work?
Yes they do.
In large clinical trials:
In the STEP 1 trial (Semaglutide Treatment Effect in People with Obesity), participants lost an average of 14.9% of their bodyweight over 68 weeks (Wilding et al., NEJM, 2021).
In the SURMOUNT-1 trial, participants using tirzepatide lost up to 20.9% of their bodyweight over 72 weeks (Jastreboff et al., NEJM, 2022).
That’s big!
These medications work by mimicking a hormone (GLP-1) that reduces appetite and increases feelings of fullness, meaning people naturally eat less.
A quick note on the STEP trials
The STEP trials stand for Semaglutide Treatment Effect in People with Obesity.
STEP 1 looked at adults with overweight or obesity without diabetes.
STEP 2 focused specifically on individuals with type 2 diabetes, where average weight loss was slightly lower — around 9–10% — but still clinically meaningful.
These results are real and backed by some strong data.
But weight loss alone isn’t the full picture.
What About Side Effects?
This is the part that doesn’t always make it into social media “before and after” posts.
In the STEP 1 trial:
44% experienced nausea
31% experienced diarrhoea
24% experienced vomiting
24% experienced constipation
In the SURMOUNT-1 trial, gastrointestinal side effects were reported in up to 82% of participants, depending on dose.
Most were mild to moderate but they were common.
More serious, though less frequent, risks listed in official prescribing information include:
Gallbladder disease
Pancreatitis
Increased heart rate
Thyroid C-cell tumour warning (observed in animal studies; human relevance still being monitored)
These medications are medical treatments. They’re not meant for casual fat-loss aids.
The Muscle Loss Conversation
Here’s something especially important from a strength training perspective.
A body composition sub-study of STEP 1 (JAMA Network Open, 2021) found that around 39% of the weight lost was lean mass — which includes muscle.
Isn’t it bewildering to think that individuals also muscle! We need muscles for:
Supporting your metabolism
Protecting your joints
Improving insulin sensitivity
Shaping your physique
Helping you age well
When weight loss happens without structured resistance training and adequate protein intake, muscle loss increases , and that can make long-term maintenance harder.
At Stack House Gym, preserving muscle isn’t optional. It’s fundamental. We believe that strength training is fundamental to longevity. Imagine being 80+ and being able to climb the stairs or carry your shopping bags! We don’t underestimate the importance of weight training here.
What Happens When You Stop Taking Them?
This is one of the most important findings.
In a follow-up study (Rubino et al., 2022), participants regained approximately two-thirds of their lost weight within one year of stopping semaglutide.
That doesn’t mean the medication “failed.”
It means appetite suppression stopped and without sustainable habits in place, weight regain is common.
These medications manage appetite while you’re on them. They don’t automatically build long-term behavioural change.
When Are Weight Loss Jabs Appropriate?
According to NICE (UK) guidelines and FDA approvals, GLP-1 medications are intended for:
Individuals with BMI ≥30
Or BMI ≥27 with weight-related health conditions
When structured lifestyle interventions haven’t been sufficient
They are designed as an adjunct to lifestyle change, not a replacement for it.
That distinction matters.
Our Honest View at Stack House Gym
It is important to note here that we’re not anti-medication.
For people with clinical obesity or serious metabolic health risks, weight loss injections can be an incredibly useful tool under medical supervision.
However, for most people wanting to “drop a bit of body fat,” the most powerful first step is still:
Progressive strength training
A sustainable calorie deficit
High-protein nutrition
Daily movement
Proper sleep
Consistency over perfection
When you build muscle, improve your habits, and understand how your body works, the results don’t depend on a prescription. They depend on systems you can sustain and that’s what real transformation looks like.
The Bottom Line
Weight loss jabs are effective.
They are evidence-based.
They have a role in clinical treatment.
They shouldn’t automatically replace the foundations of health.
At Stack House Gym, we focus on long-term strength, sustainable fat loss, and building bodies that stay strong and get stronger long-term.
We have a professional and expert team of Personal Trainers who can help guide you in your goals, if in doubt speak to us and we can help direct you!
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References
Wilding JPH et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine.
Jastreboff AM et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine.
Rubino DM et al. (2022). Effect of Continued Weekly Semaglutide vs Withdrawal. Diabetes, Obesity and Metabolism.
JAMA Network Open (2021). Body composition analysis – STEP 1 trial.
NICE (2023). Semaglutide for managing overweight and obesity.