New Year Diets & How GLP-1s like Wegovy and Mounjaro Work Differently

Every January, millions embark on ambitious weight loss resolutions—only to find themselves back where they started by March. If you've experienced this frustrating cycle, you're not alone. Recent research reveals that the problem isn't lack of willpower or motivation. The issue runs far deeper: your body has biological mechanisms designed to defend your current weight, making traditional dieting strategies significantly less effective than we've been led to believe.

The Weight Set Point Theory: Your Body's Thermostat

Scientists have identified what's known as the "weight set point"—essentially, a predetermined weight range that your body actively defends through hormonal and metabolic adjustments. Think of it like a thermostat in your home: when the temperature drops below the setting, the heating kicks in automatically. Similarly, when your weight drops below your body's set point, compensatory mechanisms activate to pull you back up.

According to the NHS, over 80% of individuals eventually regain the weight they've lost through dieting alone. This isn't personal failure—it's biology. When you lose weight through calorie restriction, your body interprets this as potential starvation and triggers a cascade of protective responses:

Increased appetite through modulation of satiety hormones
Slowed metabolism to conserve energy
Heightened food-seeking behaviour through neurological changes
Enhanced food preferences for calorie-dense options

Professor Sadaf Farooqi, who leads the Genetics of Obesity Study at the University of Cambridge, emphasises that some people gain more weight and store fat from eating the same amount of food than others do, with thousands of genes influencing weight regulation. The playing field simply isn't level.

Why "Eat Less, Move More" Falls Short

For decades, weight loss advice centred on a simple equation: calories in versus calories out.

However, a groundbreaking study from the University of Liverpool demonstrated just how powerful biological forces are. Participants who lost 17% of their body weight through medication regained 67% of the lost weight within one year of stopping treatment. This dramatic rebound occurs because the body's defensive mechanisms remain active long after the diet ends.

The weight set point explains why restrictive dieting often leads to what's known as "yo-yo dieting." When you're significantly overweight and your brain's weight control centre wants to maintain that higher weight, dropping substantial amounts triggers the same physiological response as genuine starvation. Your body cannot distinguish between intentional calorie restriction and actual food scarcity.

The UK's Recognition of Obesity as a Systemic Issue

The UK government's recognition of obesity as a complex biological condition—rather than simply a personal failing—marks a significant shift in public health policy. On 5 January 2026, new advertising restrictions came into force, banning junk food adverts on television before 9pm and prohibiting all paid online advertising for foods high in fat, sugar and salt.

This landmark policy acknowledges that we're fighting against an obesogenic environment worth over £23 billion annually in the UK's fast-food and takeaway industry alone. The government estimates these restrictions will remove up to 7.2 billion calories from children's diets each year and reduce childhood obesity cases by approximately 20,000.

The fact that obesity costs the NHS over £11 billion annually underscores the scale of this public health challenge. These policy changes signal official recognition that individual willpower alone cannot overcome the systemic factors driving weight gain across the population.

Where Weight Loss Injections Work Differently

This is where modern medical treatments like Mounjaro and Wegovy represent a paradigm shift in obesity management. Rather than relying solely on willpower to overcome powerful biological signals, these medications work directly with your body's natural hormone systems to achieve sustainable weight loss.

How GLP-1 Medications Target the Set Point

GLP-1 receptor agonists—the class of medication that includes both Wegovy (semaglutide) and Mounjaro (tirzepatide)—function by mimicking naturally occurring hormones your body produces after eating. These medications:

Slow gastric emptying, keeping you satisfied for longer after meals
Reduce appetite by sending fullness signals to your brain
Regulate blood sugar levels more effectively
Address hormonal dysregulation that occurs with leptin resistance

Mounjaro goes a step further as a dual GLP-1/GIP receptor agonist, targeting two hormone pathways simultaneously. Clinical trials demonstrate that it achieves average weight losses of up to 22.5% of body weight—substantially more than the 15-16% typically seen with semaglutide-based treatments.

The Importance of Medical Support and Safety

Unlike over-the-counter diet programmes or unregulated online sources, obtaining weight loss injections through a regulated pharmacy like Happy Pharmacy ensures several critical safety measures:

Qualified Prescriber Assessment: Every patient undergoes a thorough consultation with a qualified healthcare prescriber who reviews medical history, current medications, and individual health circumstances. This personalised approach ensures treatment suitability and identifies any contraindications.

Ongoing Support: Weight loss is a journey, not a destination. Regular check-ins with healthcare professionals allow for dose adjustments, management of side effects, and monitoring of results to ensure optimal outcomes.

Genuine Medication: The rise in counterfeit weight loss medications represents a serious safety concern. Regulated online pharmacies provide manufacturer-verified medications with proper storage, handling and dispensing protocols.

Comprehensive Guidance: Professional support extends beyond simply providing medication. Patients receive advice on nutrition, lifestyle modifications and realistic expectations—all essential components of successful, sustainable weight loss.

Understanding That GLP-1 Medications Are Long-Term Solutions

One crucial consideration: GLP-1 medications are designed for long-term use, not as temporary interventions. Research clearly demonstrates that discontinuing treatment often leads to significant weight regain as the body's set point reasserts itself. This doesn't represent treatment failure—it reflects the chronic nature of obesity as a medical condition requiring ongoing management.

Think of it similarly to medications for hypertension or diabetes. We don't expect patients to take blood pressure medication for six months and then stop once their readings normalise. Obesity operates under the same principles—it's a chronic condition that responds to treatment but requires continued management.

Making Weight Loss Achievable: The Happy Pharmacy Approach

At Happy Pharmacy, we understand the frustration of failed diets and the shame that often accompanies weight struggles. Our approach centres on three core principles:

Trust Through Regulation: As a GPhC-registered online pharmacy, we operate under strict regulatory oversight. Every prescription undergoes review by qualified healthcare professionals, and all medications are sourced directly from licensed manufacturers.

Personal Support: Weight loss is deeply personal. Our qualified prescribers take time to understand your individual circumstances, health goals and concerns. Treatment plans are tailored specifically to you, not a one-size-fits-all approach.

Transparent Safety: We provide comprehensive information about potential side effects, realistic expectations for results, and ongoing support throughout your treatment journey. Safety always takes precedence over speed of weight loss.

The convenience of an online pharmacy doesn't mean compromised care. Our service replicates the thoroughness of in-person consultations whilst offering the discretion and accessibility that many patients value when addressing sensitive health concerns.

Realistic Expectations and Results

Clinical trial data provides clear benchmarks for expected outcomes with weight loss injections:

Wegovy (semaglutide 2.4mg): Average weight loss of 15% of body weight over 68 weeks
Mounjaro (tirzepatide 15mg): Average weight loss of 21% of body weight over 72 weeks

These results were achieved in combination with dietary modifications and physical activity, underscoring that medication works most effectively as part of a holistic approach to weight management.

Individual results vary based on numerous factors including starting weight, metabolic health, adherence to treatment, and lifestyle modifications. The journey requires patience—meaningful weight loss typically occurs gradually over many months rather than weeks.

Moving Beyond the Willpower Myth

Bini Suresh, head of dietetics at the Cleveland Clinic in London, articulates the crucial shift in perspective: "When patients understand that their struggle is rooted in biology, not lack of discipline, and are supported with structured nutrition, consistent meal patterns, psychological strategies and realistic goals, their relationship with food improves markedly" .

This understanding removes the burden of shame that so often accompanies weight struggles. You haven't failed at dieting—you've been fighting against biological mechanisms that evolved over millennia to protect against starvation. Modern medical treatments like Mounjaro and Wegovy simply provide tools that work with your biology rather than against it.

The UK's new advertising restrictions, the growing body of scientific evidence about weight set points, and the development of effective medical treatments all point toward the same conclusion: obesity is a complex medical condition requiring medical solutions, not moral judgements.

Taking the First Step

If you've struggled with weight loss despite genuine effort and commitment, you may benefit from a medical approach that addresses the underlying biological factors. Happy Pharmacy offers:

Convenient online consultations with qualified prescribers
Access to a variety of weight loss treatments depending on individual suitability
Ongoing support throughout your treatment journey
Regulated, safe medication delivery to your door

Understanding the science behind weight set points doesn't remove the challenge of weight loss—but it does provide realistic pathways forward that don't rely on superhuman willpower. With proper medical support, addressing the biological mechanisms that defend your current weight becomes achievable rather than an impossible battle against your own body.

This January, perhaps the most important resolution isn't to lose weight through sheer determination. It's to approach weight loss with the understanding that biology matters, medical support helps, and sustainable results require working with your body's systems rather than fighting against them.

Blog medically reviewed by : Palvinder Deol, GPhC Registered Pharmacist, 10 January 2026

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Why New Year Diets Fail: The Science Behind Weight Set Points and How GLP-1s Work Differently