The Science of GLP-1 Drugs: Weight, Addiction, and What Happens When You Stop

A series of recent studies has investigated the effects of glucagon-like peptide-1 (GLP-1) receptor agonists, such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), on weight management, addiction, and cardiovascular health. Research indicates that while these medications are effective for weight loss, their discontinuation is associated with weight regain and a reversal of certain health benefits. Additional studies have found associations between GLP-1 use and reduced impulsivity, substance misuse, and cardiovascular risks.

Weight Management and Discontinuation

Multiple studies have examined outcomes following the cessation of GLP-1 medications.

Weight Regain

A meta-analysis published in the British Medical Journal (BMJ) by Oxford University researchers, analyzing 37 studies with 9,341 participants, found that individuals who ceased GLP-1 agonists experienced an average weight regain of 0.4 kg per month, with full weight regain projected within approximately two years. This rate of regain was nearly four times faster than that observed in individuals who lost weight through diet and physical activity alone.

Modeling Regain Trajectories

A separate systematic review and meta-analysis by Cambridge University researchers, published in eClinicalMedicine, modeled weight regain trajectories from six randomized controlled trials involving over 3,200 individuals. The model projected that by 52 weeks after discontinuation, individuals had regained an estimated 60% of their initial weight loss, with regain plateauing at approximately 75% of the original loss after 60 weeks. This suggests about 25% of initial weight loss may be sustained long-term.

Real-World Outcomes

Conversely, a retrospective cohort study from the Cleveland Clinic, published in Diabetes, Obesity and Metabolism, examined nearly 8,000 patients in Ohio and Florida who discontinued semaglutide or tirzepatide. The study found that patients did not experience significant weight regain on average one year after stopping. For patients treated for obesity, the average weight loss before discontinuation was 8.4%; one year later, they had regained an average of 0.5%. Researchers attribute this to many patients transitioning to other treatments: 27% switched to a different medication, 20% restarted their original medication, and 14% engaged in lifestyle modification programs.

Reversal of Cardio-Metabolic Benefits

The Oxford meta-analysis in the BMJ also found that improvements in blood pressure and cholesterol levels returned to pre-treatment levels within an average of 1.4 years of stopping the medication.

A separate study by Washington University School of Medicine, published in BMJ Medicine, analyzed over 333,000 veterans with type 2 diabetes and found that cardiovascular benefits accrued during continuous GLP-1 use were largely lost within 1.5 to 2 years of discontinuation. Patients who continuously took GLP-1s for three years showed an 18% lower risk of heart attacks, strokes, or death compared to those on sulfonylureas. Two years after discontinuation, this benefit was effectively erased.

Dr. Ziyad Al-Aly, a clinical epidemiologist, described the reversal of cardiovascular benefits after discontinuation as "metabolic whiplash," noting that benefits built over three years could be erased within approximately 1.5 years.

Addiction and Impulsivity

Several studies have explored the relationship between GLP-1 medications and substance use or impulsive behavior.

Substance Use Disorders

A study of over 600,000 US veterans with type 2 diabetes, published in the BMJ, found that GLP-1 use was associated with a reduced risk of developing new substance use disorders. Compared to those using another diabetes medication (SGLT2 inhibitors), GLP-1 users without a prior addiction diagnosis showed:

• An 18% lower risk for alcohol use disorder
• A 20% lower risk for cocaine use
• A 25% lower risk for opioid use

For individuals with an existing substance use disorder, GLP-1 use was associated with a 39% reduction in overdoses and a 50% reduction in deaths over a three-year period.

Alcohol Use Disorder

A randomized controlled clinical trial involving 108 patients with alcohol use disorder and obesity found that those receiving semaglutide experienced a 41.1% reduction in heavy drinking days over 26 weeks, compared to a 27.4% reduction in the placebo group. All participants also received cognitive behavioral therapy. The study was published in The Lancet.

Impulsivity and Violent Behavior

A study published in Criminology analyzed survey data from 7,521 US adults, including 821 who had used a GLP-1 medication. The study found that the association between impulsivity and violent behavior was approximately 62% weaker among current GLP-1 users compared to former users. The association between alcohol use and violent behavior was about 52% weaker among current users. The researchers noted the study was observational and could not establish causation.

"The closest thing I've seen to miracle drugs" — David Cummings, professor of medicine at the University of Washington, describing GLP-1 medications.

Adherence, Discontinuation, and Usage Patterns

Research has documented patterns of use, reasons for discontinuation, and the potential effects of intermittent treatment.

Long-Term Adherence

A research letter published in JAMA found that fewer than one in four patients remained on a GLP-1 medication after one year, based on an analysis of insurance claims data. A separate survey by market-research firm Kantar found that 74% of people who stopped taking GLP-1 drugs reported being likely or very likely to restart them.

Reasons for Discontinuation

A study from the Cleveland Clinic, published in Obesity, identified the primary reasons for discontinuation of GLP-1 medications. Of 288 patients analyzed:

• Financial reasons (insurance denial, cost) accounted for 47.6% of discontinuations
• Drug side effects for 14.6%
• Medication shortages for 11.8%

Potential Effects of Intermittent Use

A study from the University of Pennsylvania found that cycling mice on and off semaglutide led to weight gain and fat accumulation after two cycles, suggesting the drug may become less effective with intermittent use. Researchers noted this was a mouse study and more research is needed in humans.

Associate Professor Samantha Hocking, an endocrinologist, stated that the body responds to weight loss by increasing hunger hormones, making long-term treatment consistent with the understanding of obesity as a biological condition.

Market Competition and Drug Development

The pharmaceutical market for GLP-1 medications is evolving with increased competition.

Novo Nordisk, the manufacturer of Ozempic and Wegovy, forecasted a 13% decline in sales for the current year due to increasing competition and pricing pressures. Eli Lilly's Mounjaro has become Australia's highest-selling prescription medication brand, surpassing Ozempic.

Eli Lilly is developing next-generation obesity drugs, including retatrutide and orforglipron, which activate multiple receptors. Novo Nordisk has launched a pill form of Wegovy in the US and is working to make it available in Australia. Industry sources note that oral medications may improve patient accessibility and adherence.

Expert and Patient Perspectives

Patient Experience

Sarah Le Brocq, who has experienced obesity, reported losing approximately 51 kg (112 lb) over two years while using GLP-1 medications. She described a reduction in thoughts about food, increased energy, and improved quality of life.

Medical Expert Statements

• David Cummings, professor of medicine at the University of Washington, described GLP-1 drugs as "the closest thing I've seen to miracle drugs" and stated that obesity is becoming a "mitigatable" issue.
• Associate Professor Samantha Hocking, an endocrinologist, stated that the body responds to weight loss by increasing hunger hormones, making long-term treatment consistent with the understanding of obesity as a biological condition.
• Dr. Ziyad Al-Aly, a clinical epidemiologist, described the reversal of cardiovascular benefits after discontinuation as "metabolic whiplash," noting that benefits built over three years could be erased within approximately 1.5 years.

Common Mistakes and Management Strategies

Experts have identified common mistakes individuals make when starting GLP-1 medications and strategies for effective management.

Common Mistakes Identified by Experts

• Reliance on medication alone without dietary changes or physical activity
• Insufficient nutrient intake, particularly protein, leading to muscle loss
• Neglecting physical activity, especially strength training
• Increasing doses too quickly, which can cause side effects
• Not managing side effects such as nausea and constipation with dietary adjustments

Strategies for Success

• Prioritizing a nutrient-dense diet with adequate protein and fiber
• Engaging in consistent physical activity, including strength training
• Monitoring mental and emotional health during weight loss
• Undergoing proper medical evaluation and monitoring during treatment
• Integrating pharmacotherapy with behavioral support and long-term care planning