GLP-1 Diet: How Much Weight Can You Lose? Research-Backed Effects and What Happens After Stopping

Medications used in GLP-1 diets have been reported in research to reduce body weight by approximately 5–18%[1]. With daily injections of liraglutide 3.0 mg, there was approximately 8% reduction over 56 weeks[2]. However, the study subjects were obese individuals, and it has been found that side effects such as nausea are common and that weight tends to return when the medication is stopped[3][4].

How does GLP-1 medication work?

GLP-1 medication makes you feel full more easily and slows the rate at which food leaves the stomach[5]. As a result, the amount you eat naturally decreases.[5].

In research, the medication is used in combination with dietary revision and exercise, not medication alone[6]. Viewing the medication as a "tool to make it easier to reduce food intake" can reduce the gap between expectations and reality.

How much does body weight decrease?

While the range varies by study, body weight reductions of approximately 5–18% have been reported.[1]In actual clinical practice, results tend to be slightly smaller than in research studies.[1].

In a summary of studies with non-diabetic participants, the percentage of people whose body weight decreased by 5% or more was 65.3% with liraglutide 3.0 mg and 27.7% without medication[7]. Converting to ten people, this represents a difference between approximately 6–7 people and 3 people.

Even with the same type of medication, effectiveness varies. In a 68-week head-to-head comparison, semaglutide given once weekly showed 15.8% reduction, while daily liraglutide showed 6.4% reduction[6][8].

How often do side effects such as nausea occur?

Gastrointestinal side effects are common; you should anticipate them. A summary of studies in obese individuals showed gastrointestinal side effects such as nausea and diarrhea in 47–84% of participants (13–63% in the placebo group).[4].

Nausea and vomiting were reported to occur in approximately 70%, and 43.8% of those who discontinued the medication did so for this reason.[2]Most cases were mild to moderate in severity and typically temporary.[7][8].

Although infrequent, pancreatitis (pancreatic inflammation) and gallbladder disease are also noted as precautions.[5]Additionally, since muscle mass is easily lost when food intake decreases, adequate protein intake and combining with resistance training are recommended.[4].

Does body weight return after stopping?

Body weight tends to return after stopping. After using semaglutide for 20 weeks, those who continued showed an additional 7.9% reduction by week 68, while those switched to placebo gained 6.9%.[3].

A challenge identified is that few people continue long-term, and weight subsequently returns.[1]Planning for diet and exercise when stopping before you begin can provide peace of mind.

Who is it suitable for? Can non-obese people use it?

What has been confirmed in research is use in obese individuals. Representative trials targeted adults with BMI 30 or higher, or those with hypertension and BMI 27 or higher.[6].

No studies were found in the scope of this research examining the efficacy and safety of use in non-obese individuals for cosmetic purposes. Please note that the lower someone's BMI, the less directly the research results can be applied.

If you are scheduled for surgery or anesthesia, you must tell your healthcare provider you are using this medication. It is recommended to discontinue daily medications on the day of surgery and weekly medications for 1 week before surgery[9].

What should you confirm before starting?

During counseling, ask about the following points.

Goal: What percentage of weight loss are you aiming for, and is this appropriate for your BMI?[1][6]

Side effects: If nausea is severe, are there options to reduce the dose or take a break?[4][2]

Existing conditions and surgery: Do you have a history of pancreatitis or gallbladder disease, or upcoming surgery?[5][9]

How to stop: After stopping, how will you continue diet and exercise to prevent weight from returning?[1][3]

Whether GLP-1 medication is suitable for you, and what dose and duration are best, cannot be determined by an article alone. During your consultation, inform your doctor of your current BMI, existing conditions, and any medications you are taking, and confirm the approach if side effects occur and when you decide to stop.