By Aline Bouto, Certified Personal Trainer
You’ve probably seen someone claiming that Mounjaro makes you lose weight fast, right? But I need to tell you something almost no one talks about: 
It doesn’t work alone.And that is exactly why so many women are spending money, facing side effects… and gaining all the weight back once they stop the medication.
I’ve been receiving many messages from my clients saying: “Aline, I started taking Mounjaro, but I stopped and started gaining weight again,” or “Aline, I’m on Mounjaro and I’m losing a lot of muscle.” Messages like these motivated me to write this because I understand the frustration of seeing the scale go up again and seeing your body become “saggy” due to muscle loss.
In this article, I — Aline Bouto, a personal trainer for 14 years and a weight loss specialist for moms — will explain in simple terms how Mounjaro actually acts on the body, the difference between losing weight and losing fat, and what you need to do for real, lasting results.
Weight Loss vs. Fat Loss: Yes, there is a difference!
People often confuse the two, but they are very different things.
- Fat Loss (True Slimming): Losing fat while maintaining (or gaining) muscle mass.
- Weight Loss: Simply losing anything—muscle, fat, and water.
After I became a mom, I went through a period where my weight dropped fast, but the mirror didn’t show what I expected. That’s when I understood: I saw my body “wilt” due to the lack of muscle postpartum. Losing muscle slows down your metabolism, increases fatigue, and leaves your body more prone to the “yo-yo effect”—especially if you are a mom already feeling tired and lacking energy in your daily life.
How Mounjaro Acts on Your Body
Mounjaro does not burn fat.It does not accelerate the metabolism.It also does not increase caloric expenditure. What it really does is decrease the appetite. It slows down the emptying of your stomach, which makes you eat less – but without a proper strategy, this leads to muscle loss along with fat.
💡 Studies show that up to 25% of the weight lost can come from muscle mass during use.
I have followed students who used the drug and lost weight quickly, but without training and not enough protein, they reported loss of energy and strength – clear signs of muscle loss.
When you lose muscle:
• Metabolism slows down
• The body enters defense mode
• And when you eat normally again, it stores fat faster
This is the famous rebound effect.
The body learns to survive with less and then “cobra” it back.
Why do so many people gain weight back?
Because Mounjaro alone does not teach the body to function better – it only reduces hunger temporarily.
Without strengthening the muscle and adjusting the lifestyle, the body “gets addicted” in this form of energy saving.
What about the result?
As soon as the medicine is stopped, the weight returns… and usually in fat.
It’s as if the body says, “Ok, she stopped depriving me, now I’ll save everything I can.” This is one of the things I see happening among women who try quick solutions.”
How to use Mounjaro the right way
If you are using—or intend to use—Mounjaro, that’s fine. But what will make a real difference is how you manage the process. Note these fundamental pillars:
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Strength training at least 3x a week
It is the only type of training capable of preserving and increasing your lean mass. With my personal students, all do strength training – and this is where the body really changes, because it begins to have muscle gain, decreasing flaccidity, increasing metabolism and enhancing weight loss.
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Eat protein at every meal
- It will be challenging, because the digestion of protein is slower and can generate discomfort, but it is essential not to lose muscle. In this case, prefer the animal proteins that they have a higher protein value enhancing muscle gain.
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Drink enough water
The rule is simple: 35 ml per kg of body weight (approx. 0.5 to 1 oz per pound). If you weigh 70 kg (154 lbs), you need about 2.4 liters (82 oz) a day—after all, over 80% of muscle is water. I often tell my clients to use marked bottles or phone alarms.
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Have a good sleep routine
Poor sleep also causes muscle loss and slows down the metabolism.
The Path to Real Transformation
When you combine the Mounjaro (if any) with strength training, good nutrition, hydration and adequate sleep, the result changes completely.You lose weight with health, maintain your muscles and keep burning fat even without medicine. The focus isn’t just on losing weight – it’s reprogramming your body to work the right way.Mounjaro may be a momentary ally, but he will never be the protagonist of your weight loss.What truly transforms is the lifestyle you build while using (or after stopping).
