Jump to: How does Mounjaro work? | Signs of losing weight too quickly | Understanding weight fluctuations | Monitoring your progress | When to adjust your approach | Take home message
If you’re losing more than 2 lbs a week on Mounjaro that persists for longer than 4 weeks, you’re probably losing weight too quickly.
While Mounjaro (tirzepatide) can lead to significant weight loss in the first few weeks of treatment, research shows the average rate typically settles to around 0.45-0.9kg (1-2 pounds) per week after the initial period.
This rate of weight loss allows for sustainable fat loss while preserving essential lean tissue.
Data from randomised controlled trials shows that people taking Mounjaro lose an average of 6% of their body weight in the first eight weeks.
While this might seem rapid, much of this initial weight loss comes from water and stored carbohydrates (in the form of glycogen) rather than fat tissue.
Our bodies are complex systems that have evolved to protect us against starvation. When we lose weight too quickly, our bodies can trigger protective mechanisms that may work against our long-term health and weight management goals.
A study of 101 women found that those following a severe calorie restriction lost 1.5 times more lean mass and 2.5 times more bone mineral density than those following a moderate approach.
How does Mounjaro work?
Mounjaro works by mimicking two hormones, GLP-1 and GIP, that communicate with our brain’s appetite control centre.
This dual action helps reduce hunger and food-seeking behaviour, naturally leading to lower calorie intake.
Clinical trials show varying weight loss results on Mounjaro depending on dosage:
- 5mg weekly: Average loss of 16.1kg after 72 weeks
- 10mg weekly: Average loss of 22.2kg after 72 weeks
- 15mg weekly: Average loss of 23.6kg after 72 weeks
These figures translate to an initial rate of around 1.6 pounds per week in the first two months, naturally slowing to about 1 pound per week over time. This gradual reduction in the weight loss rate is normal and healthy.
Still, some people might be considered ‘hyper-responders’ to the medication and struggle to eat as their hunger levels essentially go down to zero.
In this scenario, it’s very likely that some people on Mounjaro will be losing weight quicker than is recommended.
Signs of losing weight too quickly
Your body provides several signals that might indicate overly rapid weight loss:
Fatigue and weakness often occur when calorie intake is too low to support basic bodily functions. Your brain requires consistent energy to function optimally, and severe restriction can impact concentration and mood.
Hair thinning or loss affects approximately 5-10% of people during rapid weight loss. This occurs because your body prioritises essential functions over hair growth when resources are limited.
Feeling unusually cold might indicate your metabolism has slowed significantly to conserve energy, a natural response to severe calorie restriction.
The role of metabolic adaptation
When we lose weight rapidly, our bodies undergo a process called metabolic adaptation.
This natural protective mechanism involves reducing energy expenditure to prevent excessive weight loss and preserve essential functions.
In simple terms, the number of calories our body burns each day decreases as the body seeks to maintain fat levels in the body.
Research shows this adaptation can persist even after weight loss stops, making it harder to maintain results long-term.
The effect of metabolic adaptation and the long-term impact on our metabolism is why a gradual approach typically leads to more success in the long term.
Nutrition strategies for healthy weight loss
Focus on eating three balanced meals daily, even if your appetite is reduced. Each meal should contain:
- A protein source the size of an open hand (25-30% of your plate)
- Complex carbohydrates the size of one closed fist (25% of your plate)
- Vegetables the size of two open hands (50% of your plate)
- A source of fat from whole foods
- Include 1-2 servings of fruit per day, like berries in breakfast or an apple with your lunch
Protein intake is particularly crucial during weight loss. Aim for 1.6-2.2g of protein per kilogram of body weight per day (around 20-40g in each meal) to preserve muscle mass and support metabolic health.
Understanding weight fluctuations
Daily weight changes don’t necessarily indicate actual fat loss or gain. Several factors influence these fluctuations:
Glycogen storage affects water retention – for every gram of carbohydrate stored, your body holds approximately 3-4 grams of water. This explains why reducing carbohydrate intake often leads to rapid initial weight loss.
Sodium intake influences fluid balance, with higher sodium consumption typically leading to increased water retention. This is why weight often fluctuates after consuming restaurant meals or processed foods.
Hormonal changes, particularly during the menstrual cycle, can cause weight to fluctuate by 0.5-1.5kg due to water retention. This is normal and doesn’t reflect true fat loss or gain.
Monitoring your progress
Track your weight loss journey using these strategies:
If you want to weigh yourself, do so at the same time each day, preferably first thing in the morning after using the bathroom. This provides more consistent measurements.
Take monthly body measurements and log how your clothes are fitting, as the scale doesn’t tell the complete story. Changes in body composition often occur even when weight remains stable.
Keep a food diary focusing on meal timing and protein intake rather than strict calorie counting. This helps ensure you’re eating enough to support healthy weight loss.
When to adjust your approach
You’re probably losing weight too quickly if you notice any of the following:
- Persistent fatigue or weakness
- Difficulty sleeping
- Regular headaches
- Mood changes
- Constant hunger or extremely low appetite
Contact your healthcare provider if you consistently lose more than 0.9kg (2 pounds) weekly after the first month. They may need to adjust your medication dosage or provide additional support.
Focus on developing sustainable habits that support your health beyond weight loss. This includes:
- Regular meal patterns that fit your lifestyle
- Eating a diet based on whole foods rich in protein, fat, complex carbohydrates, and fibre
- Enjoyable forms of physical activity
- Stress management techniques
- Adequate sleep routines
- Social support systems
Take home message
While Mounjaro can be an effective tool for weight loss, the goal is to lose weight in a way that supports your long-term health and quality of life.
Focus on building sustainable habits, eating a diet based on whole foods, and regular movement rather than rapid results on the scales.
Remember that everyone’s journey is different, and what matters most is finding an approach that works for you while maintaining your health and wellbeing.
Second Nature’s medication programmes
Second Nature has two medication-supported programmes: a Wegovy weight-loss programme and a Mounjaro weight-loss programme.
Why should you choose Second Nature over other medication providers if you’ve decided to try Mounjaro or Wegovy (assuming you’re eligible)?
For peace of mind.
Second Nature has worked with the NHS for over 6 years, providing weight-loss programmes across the UK.
While our Wegovy and Mounjaro weight-loss programmes are private and not currently used by the NHS, we’ve built the programmes focusing on scientific evidence, patient safety, and data security.
We hope that our 6+ years of working with the NHS and building a track record of effective weight-loss results will give you peace of mind to give us a try.
