Deep Dive: Weight-Loss Injections—How Do GLP-1 Medications Work, and What Role Does Diet Play?

The so-called "weight-loss shot" is one of the most talked-about developments in the field of weight management. Medications such as semaglutide and tirzepatide can help suitable individuals achieve significant weight loss. At the same time, there is growing interest in the role that diet, exercise, and dietary supplements can play in this process.

But what exactly is behind the weight-loss injection? Who is a candidate for this type of therapy? What can it achieve—and what are its limitations? And what role do diet and so-called GLP-1 supplements play?

A look at the mechanisms of action and the current body of research helps provide a nuanced understanding of the topic.

What is the weight-loss injection?

"Weight-loss injection" is not a medical term. It refers to various prescription medications that are used to treat overweight and obesity under certain conditions.

One well-known active ingredient is semaglutide. It belongs to a class of drugs known as GLP-1 receptor agonists. GLP-1 stands for glucagon-like peptide-1 and refers to a hormone produced naturally by the body that plays a role in regulating hunger, satiety, and glucose metabolism, among other things.

Semaglutide mimics the action of GLP-1 and specifically activates the corresponding receptor. Tirzepatide also acts on the GIP receptor, thereby combining two hormonal signaling pathways.

Weight loss does not result simply from direct “fat burning.” A key component of the drug’s effect is its ability to influence hunger and satiety, thereby reducing energy intake. Regarding semaglutide, the European Medicines Agency (EMA) notes, among other things, increased satiety as well as a reduction in food intake, hunger, and cravings.European Medicines Agency (EMA)

Who is a weight-loss injection suitable for?

GLP-1-based therapy is not intended for everyone who wants to lose a few kilograms.

In adults, active ingredients such as semaglutide and tirzepatide are generally approved in the EU for weight management in patients with a BMI of at least 30 kg/m² or a BMI of at least 27 kg/m² in combination with at least one weight-related comorbid condition. These may include, for example, high blood pressure, dyslipidemia, prediabetes, type 2 diabetes, or obstructive sleep apnea. Specific suitability depends on the active ingredient in question and the individual’s medical situation. (European Medicines Agency (EMA))

These medications are not used on their own, but rather as a supplement to a reduced-calorie diet and increased physical activity. (European Medicines Agency (EMA))

Therefore, the weight-loss injection is not intended as a general solution for short-term weight loss, but rather as part of a medical treatment when there is an appropriate medical indication.

The weight-loss injection is one component—not the entire solution

Current scientific evidence shows that GLP-1-based medications can be an effective aid in weight loss for appropriate patients. At the same time, studies to date make it clear that this type of therapy is not suitable for everyone and should not be viewed as a standalone solution.

Arguments in Favor of the Therapy

• Significant Weight Loss: Clinical studies show that many people with obesity can lose a significant amount of weight when treated with GLP-1-based medications. In a large semaglutide study, the average weight loss after 68 weeks was about 15%.
• Effect on Hunger and Satiety: These medications can reduce feelings of hunger and increase feelings of fullness. This can make it easier to reduce energy intake.
• Other metabolic effects: Depending on the active ingredient and the patient’s initial condition, various metabolic parameters may also improve, such as blood glucose levels and other cardiometabolic risk factors.
• Additional Support: Medication may be particularly helpful for people for whom changes in diet and exercise alone have not yet produced the desired results.

What are the limitations?

• Possible side effects: Like all prescription medications, GLP-1-based therapies can cause side effects. Common side effects include nausea, bloating, vomiting, and other digestive problems, especially at the start of treatment.
• It’s not just fat mass that is lost: Significant weight loss can result in the loss of lean body mass as well as body fat. A recent meta-analysis of 20 randomized studies involving more than 15,000 participants concluded that, with incretin therapies, approximately 25–39% of the weight lost was attributable to lean mass. At the same time, the combination of lifestyle intervention and strength training resulted in the lowest proportion of lean mass loss.
• Weight may increase again after discontinuation: In the extension of the STEP-1 study, participants regained, on average, about two-thirds of the weight they had previously lost within one year of discontinuing semaglutide.
• Individual Differences: The extent to which body weight is reduced depends on various factors—including the initial situation, the specific active ingredient, individual usage, and accompanying lifestyle changes.

What does the weight-loss injection mean for nutrition?

A common question is: Can you still eat whatever you want when using weight-loss injections?

In general, there is no comprehensive list of foods that are strictly prohibited during GLP-1 therapy. At the same time, many people experience a significant change in their appetite. This can lead to a decrease in the amount of energy consumed.

This also changes the significance of individual meals.

When overall food intake decreases, it becomes more important to make the most of the available energy by ensuring it is as nutrient-dense as possible. A balanced diet should therefore provide, in particular, sufficient protein, fiber, vitamins, and minerals.

Examples of useful components include:

• Fruits and Vegetables
• Legumes and Whole-Grain Products
• protein-rich foods such as fish, eggs, dairy products, or plant-based protein sources
• Nuts and Seeds
• high-quality vegetable oils

At the same time, gastrointestinal symptoms such as nausea, bloating, or changes in digestion may occur, particularly at the start of treatment or when the dose is increased. This, too, can alter an individual’s tolerance to certain foods.

The question, therefore, is not so much whether you can eat anything, but rather how a balanced and nutrient-rich diet can be adapted to changes in appetite and individual tolerance.

Focus on Protein and Muscle Mass

When it comes to significant weight loss, it's not just body weight that should be considered. Body composition also plays an important role.

Protein provides the amino acids the body needs to maintain and build muscle tissue. An adequate protein intake can therefore help limit the loss of lean body mass during weight loss.

Even more important is combining this with exercise: Strength training provides targeted stimulation for the muscles, while protein supplies the building blocks needed for that.

The current evidence therefore suggests that, during weight loss, it is important to monitor body composition as well as energy intake. Regular strength training, in particular, can play an important role in this regard. (PubMed)

The following points are particularly important for a sound nutrition and exercise strategy during weight loss:

• adequate protein intake
• A varied and nutritious selection of foods
• Regular strength and endurance training
• adequate fluid intake

GLP-1 Supplements: What's the Story?

As the weight-loss injection has become more widely known, dietary supplements have also entered the market, marketed as “GLP-1 Support,” “GLP-1 Booster,” or “natural GLP-1 support.”

However, there is no uniformly defined category of GLP-1 dietary supplements. Depending on the product, they may contain, for example:

• Diet ary fibers such as psyllium (or psyllium husks) or inulin
• Protein
• Prebiotics
• selected plant compounds such as berberine

What is interesting here is not so much the term “GLP-1” as the question of which physiological processes the nutrients and plant compounds it contains can actually support.

The key difference from GLP-1 medications lies in their mechanism of action: Drugs such as semaglutide or tirzepatide act specifically through certain receptors. Dietary supplements, on the other hand, target other physiological processes.

Therefore, they do not have the same pharmacological effects as GLP-1 medications. At the same time, certain ingredients may offer interesting avenues for satiety, digestion, nutrient supply, and metabolism.

Dietary Fiber: Supports Satiety and Digestion

Dietary fiber is one of the most interesting components of a diet when it comes to satiety, digestion, and metabolism.

They occur naturally in vegetables, legumes, whole-grain products, fruits, nuts, and seeds. Psyllium, inulin, and resistant starch, for example, are also used as dietary supplements.

Certain soluble and fermentable dietary fibers can affect digestion and contribute to satiety. When fermentable dietary fibers are broken down by the gut microbiota, short-chain fatty acids, among other substances, are produced. These, in turn, can influence signaling pathways associated with the regulation of appetite and satiety, including the release of GLP-1 and PYY.

Dietary fiber is thus an interesting example of how diet can influence natural physiological processes—without this implying a pharmacological GLP-1 effect.

An adequate intake of dietary fiber is therefore an important part of a balanced diet and can support various processes related to satiety and metabolism.

Berberine and Other Plant Compounds

Berberine and various plant extracts are also increasingly being studied in relation to metabolism and weight management.

Berberine occurs naturally in various plants and is used as a dietary supplement. Research is focusing, among other things, on its potential effects on glucose metabolism, blood lipids, and body weight.

A systematic review and meta-analysis of 23 studies published in 2026 found statistically significant, though rather moderate, changes in body weight, BMI, and waist circumference. The results are interesting but should be interpreted with caution given the differences among the studies and other methodological limitations.

This makes plant compounds an interesting field of research. As with many bioactive substances, the specific compound, the dosage, and the quality of the available evidence are all important factors.

GLP-1 Medications and Diet: Two Different Approaches

GLP-1 medications and diet take different approaches. Medications such as semaglutide and tirzepatide specifically target certain hormonal signaling pathways and have been clinically studied for specific medical applications.

Nutrition and dietary supplements have a broader scope: Dietary fiber, protein, certain plant compounds, and an overall nutrient-rich diet can support various physiological processes related to, among other things, satiety, digestion, and metabolism.

The scientific evidence varies depending on the nutrient and ingredient. Dietary supplements should therefore not be equated with pharmacological GLP-1 therapy. At the same time, this does not mean that they lack physiological relevance.

What matters most is which ingredient is used, in what form, and for what purpose, and how well its effects are scientifically substantiated.

For many people, a sensible approach to weight management begins with the basic lifestyle factors: a balanced diet, adequate exercise, good-quality sleep, and a long-term dietary plan that works for them. Dietary supplements—when used appropriately—can complement specific aspects of one’s diet.

What will remain important in the long term?

Whether or not medication is used, a sustainable long-term diet and regular exercise remain key components of successful weight management.

The point is not to restrict your diet as much as possible. Rather, it is the quality of your diet that matters, especially when you are eating less overall.

The following are particularly relevant:

• an adequate protein intake
• a varied selection of foods
• an adequate intake of fiber
• an adequate supply of vitamins and minerals
• Regular exercise, especially strength training

Viewed in this light, GLP-1 medications, diet, exercise, and, if necessary, dietary supplements are not competing approaches. They address different aspects and can—depending on the individual situation—serve different purposes.

Conclusion: Understanding Weight-Loss Injections, Diet, and Dietary Supplements

GLP-1 medications such as semaglutide and tirzepatide have expanded the options for medical weight management. Their effects have been well-studied scientifically and can serve as an important component of treatment for people with an appropriate medical indication.

At the same time, they are not the entire solution. The quality of weight loss, the intake of essential nutrients, the preservation of muscle mass, and sustainable long-term habits remain important factors.

Diet and certain dietary supplements also offer various ways to support physiological processes related to satiety, digestion, nutrient supply, and metabolism. Dietary fiber, protein, and selected plant compounds are particularly interesting areas of research in this context.

The key question, therefore, is not necessarily “weight-loss injections or diet?” but rather which approach makes sense for the specific situation and how different components can work together effectively.

Scientific Note

This article is intended solely for general informational purposes and is not a substitute for medical advice, diagnosis, or treatment. The information regarding dietary supplements does not constitute a recommendation to take specific products or ingredients. Whether medication is appropriate for weight loss should be discussed on an individual basis with a doctor.

Sources

1. European Medicines Agency (EMA): Wegovy (semaglutide) – Product Information and Approval. (European Medicines Agency (EMA))
2. European Medicines Agency (EMA): Mounjaro (tirzepatide) – Product Information and Approval. (European Medicines Agency (EMA))
3. Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 2021. (European Medicines Agency (EMA))
4. Wilding JPH et al. Weight Regain and Cardiometabolic Effects After Discontinuation of Semaglutide: The STEP 1 Trial Extension. Diabetes, Obesity and Metabolism, 2022. (PubMed)
5. Eisa N, Barood O. Changes in Lean Mass With Incretin Therapy Versus Lifestyle Intervention: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Diabetes, Obesity and Metabolism, 2026. (PubMed)
6. The Role of Dietary Fiber in Regulating Appetite: An Overview of Mechanisms and Effects on Weight. Critical Reviews in Food Science and Nutrition, 2023. (PubMed)
7. Vahed IE et al. The effect of berberine on obesity indices: a systematic review and meta-analysis. International Journal of Obesity, 2026. (PubMed)