The real reason Mounjaro stops working for so many people… and the simple steps to get it back on track: Our expert reveals the mistake so many are making with jabs and how to supercharge yours

For a while, weight loss jabs like Ozempic and Mounjaro seemed like miracle drugs. People who had spent years obsessing over calories and crash dieting found the ‘food noise’ had disappeared overnight. For many who’d struggled endlessly with obesity – and the mental and physical health issues it can bring – the scales finally began moving.

But over the past few months, it’s become very apparent that even with GLP-1s, the honeymoon period doesn’t last forever. People who originally experienced pretty gob-smacking results are wondering why the weight loss has stopped just as fast as it started, despite them not yet being their ideal ‘healthy’ weight. 

So, why does Ozempic suddenly ‘stop working’? According to Kirsten Davies, health coach at CheqUp, ‘GLP-1 medications such as Ozempic, and dual GIP/GLP-1 medications such as Mounjaro, can be powerful tools for weight loss, but they’re not magic. They work by helping regulate appetite, satiety and food intake, but without supportive lifestyle habits around nutrition, movement, hydration and self-care, people may not get the results they expect.’

Even more eye-opening? Davies says many people unknowingly make the process harder for themselves by falling into habits that prevent GLP-1s from working properly. From skipping breakfast to accidentally under-eating, here are the most common mistakes she sees that are stopping you from losing those last stubborn pounds. 

You’re skipping meals because you’re ‘not hungry’

One of the biggest mistakes people make while taking weight loss injections is assuming they should eat as little as possible. And because appetite is dramatically reduced in the early stages – so much so that eating can actually feel nauseating – breakfast is usually the first thing to disappear.

‘I understand it’s easy to wake up not feeling hungry and thinking: “I’ll just wait and eat later,”’ says Davies. But while that might sound harmless, she explains that the body still needs nourishment, even when hunger cues are effectively switched off. ‘Skipping meals – especially breakfast – can place additional stress on the body and contribute to energy crashes, cravings and blood sugar fluctuations later in the day,’ she explains.

This matters even more on GLP-1 medications, Davies adds, where protein, fibre and hydration all help support the drug’s efficacy. She recommends aiming for around 30g of protein within an hour of waking, whether that’s eggs, Greek yoghurt or a protein shake. ‘This can also support fatigue management and help reduce the impact of early side effects while your body adjusts,’ she adds.

You’re not eating enough protein or fibre

‘This is a biggie,’ Davies says. While most people become hyper-focused on calories once they start Ozempic or Mounjaro, many forget to think about what’s actually on the plate. But according to Davies, protein and fibre become even more important during weight loss injections, because appetite can drop so dramatically that your body stops getting sufficient nutrients.

Protein helps preserve muscle mass while losing weight, while fibre supports digestion and helps people stay fuller for longer. Without enough of either, Davies says she commonly sees people struggling with fatigue, constipation and intense cravings as the body adapts to slower digestion and changing appetite signals.

And the reality is that many typical ‘diet’ meals are surprisingly low in both these food groups. Soup and toast, cereal bars, smoothies or tiny salads might sound healthy, but they’re often nowhere near substantial enough to nourish someone who’s eating significantly less overall.

‘I also recommend prioritising protein intake to support fat loss while helping preserve lean muscle mass,’ Davies explains. ‘As appetite changes, nutrition targets may need adjusting to make sure your body is still getting what it needs.’

You’re combining GLP-1s with intermittent fasting

For years, intermittent fasting has been sold online as the answer to almost everything: weight loss, inflammation, energy, longevity, even dull skin. But Davies says layering it on top of GLP-1 medication can sometimes tip people too far into restriction, and actually make their medication less effective.

These medications already naturally suppress appetite and slow digestion, meaning people are usually eating far less than normal anyway. Adding strict fasting windows on top can leave people feeling weak and dizzy, particularly because natural hunger cues may already be muted.

‘GLP-1s are already supporting appetite regulation,’ Davies explains. ‘Adding extra restriction can sometimes lead to nutrient gaps, fatigue and inconsistent results.’

There’s also a psychological side to it. Many people become so focused on trying to ‘maximise’ weight loss that they assume more restriction automatically means faster results. But in reality, under-eating often leaves people feeling miserable, exhausted and more likely to binge later on.

Instead, Davies recommends consistency over extremes: eating regularly and giving the body time to adjust rather than treating the injections like a crash diet.

You’re expecting the medication to do all the work

There’s a growing belief online that once you start Ozempic or Mounjaro, the weight should simply fall off without much effort. But Davies says that mindset is one of the biggest reasons people end up disappointed.

‘GLP-1 medications can help regulate hunger, but they’re not a replacement for looking after yourself,’ she explains. In reality, many people end up eating less but moving less too, surviving on coffee because they’re rarely hungry and assuming the medication somehow cancels out poor sleep or ultra-processed food.

Davies says resistance training is particularly important when taking GLP-1s because rapid weight loss can mean muscle loss too. ‘It’s not just about seeing the number on the scales fall, it’s about maintaining strength, supporting metabolic health and building habits that help you keep the weight off long term.’

Or as she puts it more bluntly: ‘The medication is a tool, and a powerful one, but you’re still the one steering the ship.’

You’re not using the injection pen properly

It sounds obvious, but Davies says incorrect use of injection pens is more common than people think – particularly among first-time users who are nervous about administering the medication themselves.

With Mounjaro’s KwikPen especially, she explains that people need to carefully follow the instructions provided, including checking the pen before use, selecting the correct dose and making sure the medication has actually been delivered properly. Rotating injection sites also matters more than many realise.

And while it can feel tempting to simply muddle through if you’re unsure, Davies warns against guessing. ‘If you’re unsure, don’t guess,’ she says. ‘Speak to your provider, pharmacist or prescriber so they can guide you safely.’

Incorrect use can affect how much medication you’re actually receiving, which may impact both progress and side effects without people even realising it.

You’re unprepared when you travel

Weight loss injections are not particularly low-maintenance travel companions. According to Davies, many people forget that medications like Ozempic and Mounjaro often require temperature-controlled storage and proper documentation when travelling – particularly abroad. The result is people arriving at airports with no cooling pouch, no paperwork and no clue whether they’ll actually be able to take the necessary doses overseas. 

‘If you’re travelling with medication, plan ahead,’ Davies says. ‘You may need a medical cool pouch, an airport security letter and advice around temperature-controlled travel.’

Time zones can also complicate dosing schedules more than people expect, especially on long-haul trips. And while one disrupted week may not sound hugely significant, inconsistency can sometimes worsen side effects or interrupt progress, particularly while you’re in the early stages of taking Ozempic. 

You’re trying to do the whole thing alone

One of the most underestimated parts of GLP-1 injections is how emotional the process is. ‘Weight loss isn’t just physical, it can be deeply emotional too,’ Davies explains. And while social media tends to focus on dramatic before-and-afters, the reality is that many users feel anxious watching just how quickly their body is changing or the presence of physical side effects.

‘I’ve seen time and again that the people who check in regularly, talk openly about their wins and struggles, and feel supported throughout the process often make the most sustainable progress,’ Davies says. Because while the injections themselves may help quieten hunger, they can’t magically fix stress, emotional eating, exhaustion or years of complicated eating habits overnight.