GLP-1 medications have received a lot of attention over the past several years, and for good reason. They've changed the game for weight loss, helping people who have struggled with their weight for years finally see the results they've been searching for.
The transformation photos are incredible, and losing a significant amount of weight is an impressive accomplishment, with or without the help of medication.
But there's an important distinction that often gets overlooked: losing weight and improving body composition aren't necessarily the same thing.
At Inertia, weight loss can be a sign that we're moving in the right direction, but it isn't the whole picture. We don't just care about the number on the scale. We care about what your body is actually losing: fat versus muscle.
GLP-1s can be an incredibly effective tool for weight loss, but they aren't a magic medication. Strength training, proper nutrition, and sustainable habits still play an essential role in improving body composition, preserving muscle, and supporting long-term results.
What Are GLP-1s, and How Do They Actually Work?
GLP-1, or glucagon-like peptide-1, is a hormone naturally produced in the body. It helps regulate blood sugar, slows stomach emptying, and influences appetite and satiety.
GLP-1 medications mimic the effects of this hormone, helping individuals feel fuller for longer and reducing hunger.
These medications were initially developed to help manage Type 2 diabetes, but their significant effects on appetite and weight loss eventually led to their use as treatments for obesity.
Two of the most common medications are:
Semaglutide: Sold under brand names including Ozempic and Wegovy.
Tirzepatide: Sold under brand names including Mounjaro and Zepbound.
Other similar medications have demonstrated benefits beyond just weight loss, including improvements in blood sugar management and cardiovascular health.
While these medications have several benefits, they aren't without potential side effects. Nausea, vomiting, diarrhea, constipation, and abdominal discomfort are very common, alongside other serious risks that should be discussed with a medical professional.
There's another important consideration that impacts what we specialize in at Inertia: strength and body-composition. When the number on the scale drops, how much of that weight loss is actually coming from body fat versus lean mass?
Do GLP-1s Really Work for Weight Loss?
Absolutely! GLP-1-based medications help reduce appetite and overall food intake, making it easier for individuals to maintain the calorie deficit necessary for weight loss.
And the research backs this claim.
In a large clinical trial, individuals taking semaglutide 2.4 mg lost an average of 14.9% of their starting body weight over 68 weeks, compared with 2.4% in the placebo group. Both groups also received lifestyle interventions.
Another study examining tirzepatide found average weight reductions ranging from 15% to 20.9% over 72 weeks, depending on dosage.
For someone who has struggled with obesity and weight management, these results can be life-changing.
But here's where we want to shift the conversation.
Just because the scale is moving doesn't mean every pound lost is body fat.
Are You Losing Fat or Losing Muscle?
When someone loses weight, that weight typically comes from a combination of fat mass and lean mass.
Lean mass includes muscle, but it also includes water, organs, connective tissue, and other nonfat components of the body.
This distinction matters because while reducing excess body fat can improve health, preserving skeletal muscle is important for strength, physical function, and long-term health.
Research has found that approximately 25-39% of the total weight lost during treatment with GLP-1-based medications can come from lean mass.
To put that into perspective, if someone loses 40 pounds, roughly 10-16 pounds of that weight loss could be classified as lean mass based on those proportions.
That doesn't mean they've lost 10-16 pounds of actual muscle. However, it highlights why monitoring body composition is important.
In comparison, in traditional lifestyle-based weight loss methods, about 25% of total weight loss comes from lean mass.
Regardless of which method is used for weight loss, muscle preservation should always be a priority.
Why Is Strength Training So Important While Taking GLP-1s?
One misconception surrounding GLP-1s is that because the medication is helping someone lose weight, they don't need to focus as much on exercise or nutrition.
But losing weight does not eliminate the need to maintain muscle.
When you're in a calorie deficit, your body has less energy available. Without adequate nutrition and a reason to maintain muscle tissue, some muscle loss can occur alongside fat loss.
This is where resistance training becomes incredibly valuable.
Strength training provides your body with a stimulus to maintain muscle, even while you're losing weight.
A 2026 systematic review found that approximately 26% of weight lost through lifestyle interventions came from lean mass. When resistance training was incorporated, that proportion was approximately 17.5%.
At Inertia, this is one of our biggest priorities with clients who are actively losing weight.
We want our clients to lose body fat while maintaining as much muscle and strength as possible.
We don’t just help our clients lose weight. We help them become stronger, healthier, and build habits that help them sustain their results.
What Happens When You Stop Taking GLP-1s?
GLP-1 medications can produce significant weight loss, but maintaining that weight loss after discontinuing treatment can be challenging. This is why we focus heavily on building habits to support long-term goals, not just short-term weight loss.
In the a clinical trial, participants taking tirzepatide initially lost an average of 20.9% of their body weight over 36 weeks. But over the following year, those who discontinued the medication experienced an average regain of 14% of their body weight.
This demonstrates that weight regain after discontinuing medication is a real possibility, and further solidifies the need for healthy habits alongside treatment.
Strength training, daily movement, balanced nutrition, and consistent routines are valuable whether someone continues medication or eventually discontinues it.
These habits support muscle preservation, overall health, and supports long-term weight management.
At Inertia, this is a major focus of our coaching process.
We don't just want our clients to achieve a goal. We want to help them develop the routines and skills that support their health long after they've reached it.
Are GLP-1s the Answer to Long-Term Weight Loss?
GLP-1s have revolutionized weight-loss treatment, and for many individuals, they've provided an effective option when previous approaches haven't produced the desired results.
Whether you're taking a GLP-1 medication or losing weight through nutrition and exercise alone, the same fundamental priorities remain important:
Preserve muscle. Build strength. Fuel your body. Create sustainable habits.
That's why our coaching at Inertia goes beyond simply helping clients lose weight.
We focus on progressive strength training, practical nutrition strategies, daily movement, and building routines that work with our clients' lifestyles.
Because at the end of the day, successful weight loss isn't just about how much weight you lose. It's about improving your health, maintaining your strength, and building a lifestyle that supports your results.
GLP-1s can be an incredibly effective tool. But the habits you build alongside them still matter.
