Weight Loss and Your Heart: The Benefits and Risks of Mounjaro and Wegovy
A lower number on the scales can be one part of better health. For some people living with overweight or obesity, treatment may also improve cardiovascular outcomes. But how strong is the evidence for Mounjaro and Wegovy, and can those gains fade when medication stops?
The reassuring message is that cardiovascular benefits have been demonstrated in particular patient groups. Understanding who was studied helps put both the benefits and the risks into perspective.
Research reviewed on 11/11/2026. Approximately 6 minutes to read.
From diabetes research to obesity treatment with Mounjaro and Wegovy
Wegovy’s active ingredient, semaglutide, stimulates the GLP-1 receptor. Tirzepatide, the medicine in Mounjaro, acts on GIP as well as GLP-1 receptors. Although both support weight management, their cardiovascular findings are not interchangeable.
Much of the early evidence came from diabetes trials. LEADER, reported in 2016, studied liraglutide in people with type 2 diabetes at high cardiovascular risk. Over a median 3.8 years, cardiovascular death, non-fatal heart attack or non-fatal stroke occurred in 13.0% receiving liraglutide and 14.9% receiving placebo. That was meaningful evidence for the treatment studied, rather than a guarantee for every medicine used for weight loss. [1]
Later trials broadened the question to people with excess weight without diabetes, and to obesity-related heart failure. They have moved the discussion beyond changes in weight, cholesterol or blood pressure to include actual clinical events. [2–4]
Semaglutide: evidence beyond blood sugar
SELECT recruited 17,604 adults with BMI of at least 27, established cardiovascular disease and no diabetes. All were aged 45 or over. Semaglutide 2.4 mg once weekly, added to usual care, lowered the relative risk of a combined outcome of cardiovascular death, non-fatal heart attack or non-fatal stroke by 20% compared with placebo. [2]
In practical terms, 6.5% of the semaglutide group experienced an event versus 8.0% of the placebo group over roughly 40 months. The absolute difference was 1.5 percentage points: approximately 15 fewer people with an event for every 1,000 treated during that period.
These findings supported the UK cardiovascular indication for Wegovy in adults with established cardiovascular disease and BMI of at least 27. They do not show that a younger person without cardiovascular disease will receive the same reduction, or that every semaglutide dose and formulation produces identical results. [5]
Tirzepatide: what do the newer trials tell us?
SURPASS-CVOT, published in 2025, compared tirzepatide with dulaglutide, which already has evidence of cardiovascular protection. Participants had type 2 diabetes and atherosclerotic cardiovascular disease; average BMI was 32.6, although the study was not exclusively an overweight or obesity trial. [3]
The primary cardiovascular outcome occurred in 12.2% taking tirzepatide and 13.1% taking dulaglutide. Tirzepatide demonstrated non-inferiority: it was not worse by more than the trial’s allowed margin. Superiority was not statistically established. These figures cannot be set against SELECT’s percentages to rank Mounjaro and Wegovy, because the trials used different populations and comparators.
SUMMIT addressed obesity-related heart failure with preserved ejection fraction (HFpEF). In this condition, the heart can retain a normal pumping percentage while filling abnormally. Among 731 participants with obesity, cardiovascular death or worsening heart failure occurred in 9.9% receiving tirzepatide and 15.3% receiving placebo over a median two years. Fewer worsening heart failure events drove the benefit; a reduction in cardiovascular death alone was not demonstrated. [4]
An October 2026 SURPASS-CVOT analysis found no clear difference between tirzepatide and dulaglutide in heart failure hospitalisations or urgent visits, with or without previous heart failure. This does not cancel out SUMMIT: it answers a different question using a different comparison. [12]
Does sex or age change the picture?
SELECT found no convincing evidence that the relative cardiovascular effect differed between women and men. Women lost more weight, but did not show clearly greater cardiovascular protection. Women made up only around 28% of the trial, so their separate results were less precise. [6]
Participants averaged about 62 years old, with nobody younger than 45. The results should therefore not be assumed to apply equally to younger adults. Subgroup findings have not identified an age group that uniquely benefits, while evidence in very frail older adults remains less certain. Nutrition, muscle strength, kidney function and other prescriptions all influence the individual assessment. [2,6,9]
Diabetes and heart failure need individual consideration
A person does not need diabetes to benefit: SELECT deliberately studied people without it. Previous cardiovascular events, diabetes or kidney disease can nevertheless change underlying risk, and therefore the potential absolute benefit.
In obesity-related HFpEF, semaglutide improved symptoms, physical limitations and walking performance in the STEP-HFpEF programme, including trials with and without diabetes. These findings and SUMMIT are encouraging, but should not be extended to every type or severity of heart failure. Unstable or severe disease calls for specialist review. [7]
What needs checking during treatment?
Both treatments can raise resting pulse. Vomiting and diarrhoea may lead to dehydration, kidney problems and dizziness; low blood pressure is also possible. People taking diuretics or blood-pressure medicines may need closer review. Seek prompt advice about persistent palpitations, fainting or being unable to retain fluids, and avoid changing heart medicines yourself. [8,9]
Insulin or sulfonylureas increase the likelihood of low blood sugar when used alongside these medicines. Pancreatitis and gallbladder problems also need consideration. In SELECT, 16.6% receiving semaglutide stopped permanently because of adverse events, compared with 8.2% receiving placebo. Benefit does not remove the need to assess tolerability. [2,8,9]
Suspected heart attack or stroke, collapse or sudden severe breathlessness requires a 999 call. These symptoms should not be dismissed as routine side effects.
Stopping treatment: understanding ‘metabolic whiplash’
Recent reports have highlighted the possible loss of cardiovascular protection after stopping GLP-1 medicines. The phrase ‘metabolic whiplash’ describes this concern; it is not an established withdrawal syndrome.
The tirzepatide withdrawal analysis discussed by the BHF linked weight regain with reversal of improvements in blood pressure, cholesterol and glucose. It measured risk factors, and did not establish that stopping caused more heart attacks, strokes or deaths. [13,14]
A separate 2026 observational study of US veterans with type 2 diabetes examined clinical events. Compared with continuous GLP-1 treatment, stopping for one or two years was associated with approximately 14% and 22% higher relative risk of the combined outcome of heart attack, stroke or death from any cause. These figures are not percentage-point increases or separate estimates for each event. [15]
Only 0.03% of GLP-1 users in that study received tirzepatide, so it offers little Mounjaro-specific evidence. The findings also cannot prove that discontinuation itself caused harm, or that someone’s risk became greater than if they had never started. Differences in health and other circumstances between those stopping and continuing could affect the results. [15]
How much does weight loss contribute?
Weight reduction can improve blood pressure, glucose control, mobility and other risk factors. However, better risk-factor measurements do not automatically prove fewer cardiovascular events. Look AHEAD, reported in 2013, improved weight and fitness in adults with excess weight and diabetes without significantly reducing its primary cardiovascular outcome. [10]
A 2025 SELECT analysis suggested that semaglutide’s cardiovascular protection was not explained solely by the weight lost. Additional mechanisms may contribute, although this analysis cannot establish exactly how they work. Weight management still matters. [11]
Can the cardiovascular benefits outweigh the risks?
Yes, for appropriately selected patients, particularly those at higher cardiovascular risk who tolerate treatment. Semaglutide has demonstrated fewer major cardiovascular events in the SELECT population. Tirzepatide has shown benefit in obesity-related HFpEF and cardiovascular non-inferiority to dulaglutide in high-risk type 2 diabetes. Each finding needs to stay attached to the medicine and patient group studied. [2–4]
The possibility of losing protection after stopping supports long-term planning, regular reviews and a supported transition if treatment ends. It does not mean lifelong medication is necessary for everyone, or that stopping inevitably triggers a heart attack or stroke. A serious adverse reaction may still require discontinuation; agree appropriate follow-up for weight, blood pressure, glucose where relevant, and other medicines with your prescriber. [8,9,13–15]
Sustainable weight management works alongside prescribed cardiovascular treatment, balanced meals, suitable activity and smoking cessation. Slim Transformation offers confidential, individual assessment to explore weight-management options, while your usual clinical team continues to oversee existing heart disease.
General educational information, not a substitute for personal clinical advice. Photographs are illustrative and do not show study participants.
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