Mounjaro: The Truth Behind the Quick Fix

Mounjaro for weight loss is here to stay, and with Retatrutide now moving through phase 3 clinical trials, it’s clear that this new generation of GPL-1 drugs isn’t going anywhere. As a personal trainer, I see it as part of my duty of care to help clients and future clients understand the bigger picture when it comes to using these medications safely and effectively.

While I’ve witnessed some brilliant results when Mounjaro is used correctly, I’m also horrified by stories I’ve heard (thankfully not from my own clients!) of people living off Haribos, skipping meals, and “just eating the same processed takeaway diet but less of it ” because they’re not hungry.

Let’s be clear, eating like a sparrow, cutting out proper meals, and skipping exercise is not the route to long-term success. You might be lighter on the scales, but without muscle, balance and nutrition, you’ll still be frustrated with your reflection. Especially when you throw fluctuating hormones and perimenopause into the mix, we may see slimmer bodies, but not necessarily stronger, toned, or happier ones.

What Mounjaro Does (and Doesn’t) Do

Mounjaro is an appetite suppressant; it helps you feel fuller for longer, meaning you naturally eat less. It’s not magic, and it doesn’t build muscle or tone your body. The weight loss you see often comes from both fat and muscle, which is why combining it with proper nutrition and resistance training is so important.

Here’s the bit most people forget: if your calories drop too low (for example, under roughly 1,200 a day), your resting metabolic rate. The number of calories your body burns at rest can slow down. This process, called adaptive thermogenesis, is the body’s way of conserving energy when it senses a famine. In simple terms, the less you eat, the less your body thinks it needs, so it burns fewer calories at rest.

That’s fine while you’re eating very little. But once you start eating normally again, remember: Mounjaro only works while you’re taking it. If you’re consuming more than your new, slower metabolism burns, the weight will come back.

That’s why guidance, education, and strength training matter so much before, during, and after using Mounjaro.

I’ve explored this topic quite thoroughly and highly recommend THE GLP-1 Solution book by Lyle McDonald; it’s available on Amazon. He's an author who values science, research, and evidence, and is brilliant at making complex scientific information understandable to those without a scientific background.

My Top Tips for Mounjaro Users (and Anyone Coming Off It)

1. Treat Mounjaro as a helping hand, not a magic wand.
   It’s there to support your journey, not replace the habits that keep your results. Think of it as a window of opportunity to learn how to fuel your body properly.

2. Prioritise protein and proper meals.
   Every meal should include a good source of protein, fibre, and colour. You might not feel hungry, but your body still needs nutrients to protect muscle and maintain hormone balance. While it might be tempting to increase calories by adding more fat, it's worth noting that high dietary fat intake can cause gastric issues.

3. Lift weights. If you’re not already strength training twice a week, start now. Resistance work is your best defence against muscle loss and slowed metabolism. It’s the key to staying strong, toned, and energised.

4. Don’t starve yourself.
   Under-eating is not the fix you think it is. Aim for balance, fuel your workouts, support your recovery, and trust that a well-fed body burns more efficiently.

5. Plan for the ‘after’.
   When you come off Mounjaro, your appetite will come back quickly. If you haven’t built solid habits, it’ll be hard to maintain progress. That’s why it’s so important to work with a coach, keep your strength training going, and learn how to adjust your intake gradually.

6. Stop chasing the lowest number on the scale.
   Stop focusing on the lowest number on the scale.
   Fat loss and weight loss are not the same. You can be lighter but weaker, or stronger and smaller at the same time. The difference lies in the muscle.

The Bottom Line

Weight loss is a science and a balance of numbers, calories in vs. calories out, but real success comes from how you achieve that balance. Mounjaro can help some people, but without understanding your body’s needs, you risk undoing your own progress.

To those of you currently on it, coming off it, or watching friends and family using it: stay curious, stay consistent, and remember that education and training are the real game-changers.

If you’re unsure how to support your body while using or transitioning off Mounjaro, reach out. We’ll build a plan that keeps your metabolism healthy, your muscles strong, and your results sustainable.

On the left below is Sophie, who has lost 6.5 stone. You can read her story here

PS, many choose to stay anonymous, and in our gym, we totally respect your wishes.

Kate