Weight-loss medications have become a go-to in the health and wellness world for their fast, visible results. 

Injectable options like Ozempic, Wegovy, Mounjaro, and Zepbound—commonly known as weight-loss pens—can be incredibly effective tools for reaching your goals. But here’s what many overlook: while these GLP-1 medications can jumpstart your weight-loss journey, they’re not the whole solution. As a registered dietitian, I can tell you that lasting success requires more than just the pen.

First, let’s dive into the research of how these weight-loss pens work.

Semaglutide is a GLP-1 receptor agonist that mimics a hormone called glucagon-like peptide-1. It helps regulate blood sugar, suppress appetite, and slow gastric emptying—all factors that can positively support weight loss. 

A 2021 NEJM study on Wegovy (semaglutide 2.4 mg) showed that participants lost an average of 14.9% of their body weight over 68 weeks, compared to 2.4% with lifestyle intervention alone.³

Tirzepatide (marketed as Mounjaro and Zepbound) combines GLP-1 and GIP receptor agonism and has shown even more dramatic results—up to 22.5% weight loss in clinical trials. ²

If we know that these pens work, then what is the catch? Studies have also shown that while weight loss is significant temporarily, many participants gain the weight back. 

A 2022 follow-up study found that most patients regained two-thirds of their weight within one year of stopping semaglutide.¹

Why? Because while the medication changes your biology, it doesn’t teach the long-term behaviors that sustain weight loss. This is where a dietitian comes in.

🥗 Why You Still Need a Dietitian—Even on a GLP-1 Weight Loss Pen

As a registered dietitian in Boston, I specialize in helping clients on semaglutide (and other GLP-1s) navigate the challenges of eating well, preserving muscle, and making changes that last beyond the medication. 

Here’s what the research—and real-life experience—tells us:

✅ 1. Nutrition Quality Still Matters

Appetite suppression can lead to eating less overall, but not necessarily better. Studies show that without guidance, people on GLP-1s may consume fewer calories—but also miss out on essential protein, fiber, and micronutrients [(Berglund et al., Frontiers in Endocrinology, 2023)].

Dietitians ensure you’re eating enough to:

• Preserve muscle mass
• Prevent nutrient deficiencies
• Support metabolism

All essential components to long-term weight-loss maintenance. 

✅ 2. GI Side Effects Can Be Managed With Food

Nausea, constipation, and delayed gastric emptying are common side effects of semaglutide and Tirzepatide. A dietitian can recommend food strategies (e.g., smaller, more frequent meals, fiber timing, hydration) to help minimize these issues and improve adherence.

✅ 3. Lifestyle Change = Long-Term Success

Lifestyle interventions, like nutrition counseling and physical activity, are key components of a successful weight-loss plan because behavior changes are the root of long-term change. However, navigating these changes can feel overwhelming and difficult. But with a dietitian, we can help you create small, realistic health habits that will build and give you the lasting results you are looking for.

🧭 Working With a Dietitian Can Maximize Your GLP-1 Results

My goal as a registered dietitian? To help you maximize results, feel your best, and build habits that last—long after the medication ends. Here’s how we support you:

• Protein-focused meal plans for muscle preservation
• GI symptom management with food-first strategies
• Nutrition labs and supplements if needed
• Support for mindful eating and emotional triggers
• Post-medication transition plans

Whether you’re just starting on semaglutide or you’ve hit a plateau, working with a registered dietitian helps ensure your progress isn’t just fast—but sustainable.

🔎 The Bottom Line

GLP-1 medications like semaglutide are powerful tools—but they work best when combined with expert guidance. If you’re serious about sustainable weight loss, the #1 thing you can do is work with a dietitian who understands GLP-1 therapies.

As a Boston-based dietitian, I’ve helped so many clients maximize their weight loss, avoid side effects, and build habits that stick—on and off medication.

Need support while using a GLP-1 weight loss pen like Wegovy or Ozempic?
💬 Book a free consultation with our team today. We offer in-person (where available) and virtual visits.

 

References

Rubino, D. M., Greenway, F. L., Khalid, U., O’Neil, P. M., Rosenstock, J., Sørrig, R., … & Wilding, J. P. H. (2022). Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: The STEP 4 randomized clinical trial follow-up. Diabetes, Obesity and Metabolism, 24(9), 1553–1564. https://doi.org/10.1111/dom.14630

SURMOUNT-1 Investigators. (2022). Tirzepatide once weekly for the treatment of obesity. The New England Journal of Medicine, 387(3), 205–216. https://doi.org/10.1056/NEJMoa2206038

Wilding, J. P. H., Batterham, R. L., Calanna, S., Davies, M., Van Gaal, L. F., Lingvay, I., … & Kushner, R. F. (2021). Once-weekly semaglutide in adults with overweight or obesity. The New England Journal of Medicine, 384(11), 989–1002. https://doi.org/10.1056/NEJMoa2032183