GLP-1 medications are changing the way many people approach weight management and metabolic health. But alongside the benefits, there are real, and sometimes unexpected, body reactions that can happen along the way.
In this episode, Catriona speaks with personal trainer Becky Lever about what people commonly experience when starting GLP-1s, from early side effects like nausea to longer-term changes in energy, mood, and muscle mass.
This fourth episode in the GLP-1 series focuses on how the body responds to these medications over time. Becky shares what she sees in clients, how reactions can vary, and why building good habits early makes a big difference, especially if you plan to reduce or stop treatment later.
Top 5 highlights from the conversation
1. Early side effects are common, especially nausea
Many people experience nausea at the start of their GLP-1 journey. This is one of the most frequently reported early reactions and often settles over time.
Other early changes can include food aversions and a reduced interest in eating, which links closely to the “food noise” discussed in earlier episodes.
2. Appetite changes can lead to under-eating
One of the biggest shifts is not feeling hungry in the same way as before. While this can feel positive, it can also lead to skipping meals unintentionally.
Your body still needs:
- Protein for muscle health
- Healthy fats
- Carbohydrates for energy
- Vitamins and minerals
Creating a structure around eating becomes important, rather than relying on hunger cues alone.
3. Digestive changes and hydration matter more than you think
Because GLP-1 medications slow down how quickly the stomach empties, people may notice:
- Constipation
- Feeling full for longer
- Acid reflux
Hydration becomes especially important. Not drinking enough can worsen these symptoms and contribute to fatigue.
4. Energy, mood, and brain fog can fluctuate
Some people report:
- Low energy or fatigue
- Difficulty concentrating (brain fog)
- Mood changes
These symptoms can overlap with other life stages, particularly menopause, so it’s not always straightforward to know what’s causing what. This is why ongoing monitoring and support are so important.
5. Muscle loss and long-term habits need attention
Weight loss on GLP-1s isn’t just fat loss. There can be a higher level of muscle loss too.
That’s why it’s important to:
- Include strength-based exercise
- Maintain protein intake
- Build sustainable routines
These habits become even more important if you reduce your dose or stop treatment, helping prevent weight regain and supporting long-term health.
Additional Insights
Body changes can happen quickly
Rapid weight loss can lead to visible changes such as:
- Loss of facial volume
- Skin changes
These can feel unexpected, even when weight loss is the goal.
Women may notice hormonal changes
Some women report changes in their menstrual cycle, including irregularity or differences in flow. This is another area where medical guidance is important.
Not everything is caused by GLP-1
Symptoms like fatigue, brain fog, or mood shifts may also be linked to:
- Menopause
- Existing health conditions
- Lifestyle factors
It’s important not to assume everything is medication-related without checking.
Support and monitoring are key
GLP-1 medications should always be taken under proper guidance. Having someone to speak to, whether that’s a GP or specialist, makes it easier to:
- Check what’s normal
- Adjust if needed
- Feel reassured
About the Expert
Becky Lever is a qualified personal trainer with experience supporting clients who are using GLP-1 medications alongside exercise and lifestyle changes.
I’m Becky. I started Believe Fitness & Nutrition in 2022. I am a qualified PT, online health and nutrition coach and qualified menopause specialist. I recently completed training to enhance my support for clients using GLP-1 medications. I have always had a keen interest in sport, nutrition and fitness. As a youngster, I competed in ten-pin bowling for my country worldwide and can attest to the value of staying active and healthy.
I live in Hampshire. I enjoy walking, strength training, kayaking, and cycling.
I have helped numerous men and women understand how to make better nutrition choices, learn how to exercise to achieve their goals and change habits and behaviours for a happier, healthier life.
Medical disclaimer
This content is for general information only and is not a substitute for professional medical advice. Always consult your GP or a qualified healthcare professional if you have any concerns about your health.