SURMOUNT versus STEP UP – what the most important modern studies truly tell us about obesity treatment

Obesity treatment is currently at a historic turning point. For the first time, medicine has access to pharmacological therapies capable of producing large, sustained, scientifically proven weight loss, in some cases approaching the results of bariatric surgery. Two names are now frequently mentioned in both medical discussions and the general media: SURMOUNT and STEP UP.

For many people, these names sound like competitors in a race: which one is better, which one causes more weight loss, which one is stronger. In reality, this way of thinking is overly simplistic and risks creating unrealistic expectations. SURMOUNT and STEP UP are not opposing camps, but rather two major research programmes that, from different perspectives, demonstrate the same essential truth: obesity can be treated effectively, medically, and in a personalised way, not through blame or extreme measures.

This article explains in depth what each study represents, what results were obtained, what the real differences are between them, and most importantly, how these data should be interpreted in real life.

What SURMOUNT and STEP UP actually are

The first and most important clarification is that SURMOUNT and STEP UP are not medications, but clinical trial programmes.

The SURMOUNT programme evaluates tirzepatide, a medication with a complex hormonal mechanism, approved for obesity treatment under the brand name Mounjaro. Tirzepatide has been studied in several trials (SURMOUNT-1, SURMOUNT-2, and others), including people with obesity with or without diabetes, in order to assess both efficacy and long-term safety.

STEP UP is part of the STEP programme, which evaluates semaglutide, the active substance in Wegovy. What makes STEP UP different is that it does not focus on the already established 2.4 mg dose, but on a higher dose of 7.2 mg, studied specifically for people who may require a deeper degree of weight loss.

Both programmes included adults with obesity, without diabetes, and incorporated lifestyle interventions in order to reflect real-world treatment conditions.

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Why superficial comparisons are misleading

One of the most common mistakes is comparing raw weight-loss percentages without understanding context. Seeing “–22%” in one study and “–19%” in another often leads to the conclusion that one treatment is clearly superior. In medicine, reality is far more nuanced.

The studies differ in:

• mechanism of action,
• dose escalation strategies,
• tolerability profiles,
• distribution of individual responses (not just averages),
• and clinical questions they were designed to answer.

SURMOUNT explores how far a dual-hormone therapy can go, while STEP UP explores what happens when an already proven mechanism is intensified. They do not answer the same question, and therefore should not be framed as a simple competition.

Mechanism of action – the key to understanding the results

Semaglutide, used in STEP and STEP UP, acts through the GLP-1 receptor. GLP-1 is a gut hormone that plays a major role in appetite regulation, satiety, and gastric emptying. Through this pathway, semaglutide helps reduce food intake and dampen food-related impulses.

Tirzepatide, evaluated in SURMOUNT, acts on two receptors: GLP-1 and GIP. GIP is another incretin hormone involved in energy balance and metabolic regulation. This dual action likely explains why some individuals experience very large weight reductions with tirzepatide.

However, a stronger mechanism does not automatically mean a better option for everyone. Increased potency can also mean differences in tolerability. This is why these treatments should be viewed as distinct tools, not universal solutions.

What the studies show about weight loss

In the SURMOUNT trials, tirzepatide produced average weight loss of approximately 20–22% at 72 weeks, depending on dose. A significant proportion of participants exceeded the 25% threshold, and some lost even more.

In STEP UP, semaglutide 7.2 mg resulted in an average weight loss of approximately 18–19%, compared with around 15–16% with the standard 2.4 mg dose. The difference versus placebo was substantial and clinically meaningful.

What truly matters is that the results overlap. Some people in STEP UP lost more weight than some participants in SURMOUNT, and vice versa. Averages do not describe individual outcomes. In real life, response to treatment is personal.

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Why distribution matters more than the mean

For someone considering treatment, the critical question is not the average weight loss in a study, but the likelihood of reaching a meaningful threshold. Both programmes show that:

• many participants exceed 10–15% weight loss,
• a significant proportion reach 20–25%,
• and some respond more modestly regardless of treatment.

This reinforces a central message of modern medicine: no treatment works identically for everyone. The goal is not perfection, but suitability.

Beyond the scale: metabolic health

A major strength of both SURMOUNT and STEP UP is that benefits extended well beyond the number on the scale. In both programmes, reductions in waist circumference indicated significant loss of visceral fat. Blood pressure improved, inflammatory markers decreased, and lipid profiles became more favourable.

These changes are critically important, as they translate into reduced long-term cardiovascular risk and improved overall health.

Prediabetes and diabetes prevention

One of the most valuable findings in both programmes relates to glucose metabolism. In SURMOUNT, many participants with prediabetes returned to normal glucose levels. In STEP UP, more than 80% of participants with prediabetes normalised glycaemia, and no participant receiving semaglutide 7.2 mg developed diabetes during the trial.

This shifts the narrative from “weight loss medication” to metabolic disease prevention.

Tolerability – an essential factor

Efficacy without tolerability has limited long-term value. In both programmes, the most common side effects were gastrointestinal and occurred mainly during dose escalation.

In STEP UP, the higher dose of semaglutide was associated more frequently with dysaesthesia, an unpleasant skin sensation such as tingling or burning, which was usually temporary.

In SURMOUNT, gastrointestinal effects tended to be somewhat more pronounced at higher tirzepatide doses, but most participants were able to continue treatment.

The key message is simple: tolerability varies between individuals. There is no universally “easy” or “hard” option.

Who might benefit more from each approach

While strict rules cannot be drawn, certain patterns emerge. Semaglutide, including the higher dose studied in STEP UP, may be well suited for individuals who already respond to GLP-1 therapy and require an additional step. Tirzepatide may be appropriate for those who need very large weight reductions or who have not responded sufficiently to GLP-1 alone.

The choice is not based on headlines, but on medical history, health goals, and individual response.

SURMOUNT versus STEP UP – a false rivalry

Seen correctly, these studies do not compete; they complement each other. They demonstrate that obesity treatment is becoming flexible and adaptable.

For some people, a 15% weight loss is sufficient to restore health. For others, 25% may be necessary. The fact that medicine can now address both scenarios is a major advance.

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Final message

SURMOUNT and STEP UP do not answer the question “which drug is better?”, but rather a far more important one:
Do we finally have enough tools to treat obesity as a real disease?

The answer is yes.

Choosing between semaglutide and tirzepatide, or between standard and higher doses, should never be based on internet trends, but on careful medical evaluation and clearly defined health goals.

Obesity is not a personal failure. It is a chronic disease. And today, for the first time, we have real, effective, science-based solutions.

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