Mounjaro for Weight Loss and Diabetes: Benefits, Results, and Side Effects

Introduction

Obesity is more than just a number on the scale; it is a chronic, complex medical condition that increases the risk of diabetes, heart disease, sleep apnea, liver disease, joint problems, and even certain cancers1. Traditional approaches like diet and exercise remain essential, but many people need additional support. That is where obesity medicines such as Mounjaro come in. Approved by the U.S. Food and Drug Administration (FDA) for type 2 diabetes (T2D)2 and showing remarkable promise in obesity management, Mounjaro is changing the landscape of weight-loss treatment. 

Mounjaro is the brand name for tirzepatide, a once-weekly injectable medication. It belongs to a newer class of drugs sometimes called “twincretins” because it targets two gut hormones:

• GLP-1 (glucagon-like peptide-1)

• GIP (glucose-dependent insulinotropic polypeptide)

Both of these hormones regulate blood sugar and appetite. By acting on them simultaneously, Mounjaro enhances the body’s ability to control glucose levels, reduces hunger more effectively than many older treatments, and reduces weight3.

How Does Mounjaro Help With Weight Loss?

Mounjaro helps with weight management in several ways4:

1. Appetite control: It reduces food cravings and helps people feel full faster.

2. Slower stomach emptying: This prolongs the sense of fullness after meals.

3. Improved blood sugar regulation: Keeping glucose stable reduces energy crashes that often drive overeating.

4. Metabolic effects: It supports fat loss while helping preserve lean body mass.

Evidence of Mounjaro Effectiveness

Mounjaro has been studied in large-scale clinical trials, including the SURMOUNT and SURPASS programs.

SURMOUNT 1-4 trials

SURMOUNT-1 to -4 were global Phase 3 clinical trials evaluating the safety and efficacy of tirzepatide among participants with obesity or overweight with or without T2D. Participants were randomly assigned to receive once weekly subcutaneous tirzepatide or placebo.

Table 1: Summary of efficacy of tirzepatide in SURMOUNT 1-4 trials

Trial	SURMOUNT 15	SURMOUNT 26	SURMOUNT 37	SURMOUNT 48
Study design	72-week study in adults with obesity or overweight without diabetes	72-week study in adults with obesity or overweight with type 2 diabetes.	72-week study in non-diabetic obese adults	36-week, open-label tirzepatide lead-in period followed by a 52-week study in people with obesity with or without diabetes.
Result	People lost about 15% (5 mg), 19.5% (10 mg), and 21% (15 mg) of their body weight with tirzepatide at week 72, compared to only 3% with placebo, and all results were highly significant	People lost about 2.8% with tirzepatide 10 mg and 14.7% with 15 mg, compared to only 3.2% with placebo, with weight loss being 9.6% and 11.6% greater than placebo, respectively	People on tirzepatide (maximum dose) lost about 18.4% (treatment regimen estimand) and 21.1% (efficacy estimand) of their body weight, compared to a 2.5–3.3% gain with placebo, with weight loss being 20.8–24.5% greater than placebo	During the open-label period, a 20.9% weight reduction was observed, and later, at week 88, 88 people who continued tirzepatide lost about 5.5–6.7% more weight, while those who switched to placebo regained 14–15%.

Importantly, weight loss was accompanied by improved blood pressure, cholesterol, liver fat, and waist circumference, all key factors in reducing long-term health risks.

SURPASS trials

The SURPASS studies tested tirzepatide in people with type 2 diabetes, showing how well it works both alone and alongside other treatments like insulin, in people around the world, including special studies in Japanese patients.

Table 2: Summary of efficacy of tirzepatide in SURPASS trials

Trial	SURPASS 19	SURPASS 210	SURPASS 311
Study design	40-week study in diabetic patients	40-week study in diabetic patients; tirzepatide vs semaglutide	Open label study; tirzepatide vs insulin degludec + metformin with/without SGLT2 inhibitors
Result	Tirzepatide led to weight loss of about 7 to 9.5 kg, depending on the dose.	Tirzepatide caused 1.9–5.5 kg more weight loss than semaglutide, with all differences highly significant	At 52 weeks, tirzepatide lowered weight by 7.5–12.9 kg, while insulin degludec led to a 2.3 kg gain.

Possible Side Effects2

Like any medication, Mounjaro can cause side effects. The most common are gastrointestinal and usually mild-to-moderate, especially as the body adjusts. These include:

• Nausea

• Diarrhea

• Constipation

• Vomiting

• Decreased appetite

• Abdominal pain

Most people tolerate the medication well, especially when doses are increased gradually. Rare but serious risks include pancreatitis and gallbladder issues.

Key Takeaways 

• Obesity is a chronic medical condition, not just excess weight, and it raises the risk of diabetes, heart disease, and other serious health problems.

• Lifestyle changes like healthy eating and physical activity remain the foundation of weight management, but many people need extra support.

• Mounjaro  is a once-weekly injection that works on two gut hormones to reduce appetite, improve blood sugar control, and support long-term weight loss.

• In the SURMOUNT trials, people taking tirzepatide lost an average of 15–21% of their body weight, much more than those on placebo, and benefits were sustained when treatment was continued.

• In the SURPASS trials (patients with type 2 diabetes), tirzepatide was more effective for weight loss than insulin and even semaglutide.

• Weight loss with tirzepatide also led to improvements in blood pressure, cholesterol, liver fat, and waist size, reducing long-term health risks.

• Side effects are mostly stomach-related (nausea, diarrhea, constipation, decreased appetite), usually mild to moderate, and often improve over time.

• Serious side effects are rare, but possible, so it’s important to use tirzepatide under the supervision of your healthcare provider.

Long-term treatment may be needed to maintain weight loss and health benefits.