Weight Loss Drugs & Your Health: What You Bring to the Party Matters
Weight-loss injections can be incredibly effective, but what happens to your digestive health, nutritional status, muscles and bones along the way? And what happens when you stop?
Weight-loss injections such as Mounjaro and Wegovy have completely changed the conversation around weight management. For many people, they've made losing weight possible when years of dieting haven't worked. There is also good evidence that these medications can improve blood sugar regulation and other aspects of metabolic health.
An estimated 1.6 million adults in Great Britain have used weight-loss medications over a 12-month period, with many accessing them privately. But while there's plenty of discussion about how much weight people are losing, I'm more interested in what's happening to their health along the way.
I'm certainly not against these medications. They can be life-changing for some people, and I have worked with clients who have benefited enormously. But losing weight and improving your overall health aren't necessarily the same thing. And in many cases clients have come to me after some months on the medications after learning this the uncomfortable way.
There's a saying I particularly like: What you bring to the party is what you get at the party.
What I mean is, if you already have digestive problems, nutrient deficiencies or poor eating habits before starting medication, those issues don't disappear because you're losing weight. Some may actually become more troublesome. And if you haven't changed how you eat, move or look after yourself... what happens when you stop?
That's why I think nutritional support should be part of the conversation from the beginning.
First, how do these medications work?
GLP-1 is a hormone naturally released by your intestines when you eat. It helps regulate blood sugar, appetite and digestion.
Semaglutide, sold as Wegovy and Ozempic, mimics GLP-1. They're the same active drug, although Wegovy is licensed for weight management and Ozempic for type 2 diabetes. Mounjaro contains tirzepatide, which acts on both GLP-1 and another hormone receptor called GIP.
These medications work on two of the main reasons we eat: hunger and enjoyment. They help you feel satisfied with less food, but also influence the brain's reward pathways. This may explain why some people find they're no longer constantly thinking about food or reaching for snacks. You've probably heard this described as the disappearance of 'food noise'.
They also slow gastric emptying, meaning food stays in your stomach for longer. This is part of how they work, but it also helps explain why digestive side effects are so rife.
You may also have heard of retatrutide, or 'Reta'. This acts on three receptors: GLP-1, GIP and glucagon. The clinical trial results have attracted considerable attention, but as of October 2026, retatrutide remains an investigational medication in Phase 3 development and isn't approved for routine use. I mention this because I keep being asked about it.
What if your digestive system wasn't happy to begin with?
This is where my 'what you bring to the party' saying really comes into its own.
Imagine two people starting Mounjaro. One has regular bowel movements, a varied diet and very few digestive complaints. The other already struggles with reflux, constipation, bloating or gallbladder problems. They're not going to have the same experience.
Because these medications slow gastric emptying, they can make certain existing symptoms worse. If you're already constipated, you may become more constipated. If you struggle with reflux or gastritis, you might experience more nausea, fullness or regurgitation.
I'd also want to know whether you're taking proton pump inhibitors (PPIs) for reflux, have previously had SIBO, have a history of gallstones or are already restricting lots of foods because they upset your stomach. These are all relevant pieces of the puzzle.
PPIs reduce stomach acid, which is important for normal digestion and the release of certain nutrients from food. Long-term use can be associated with some nutritional deficiencies, including vitamin B12 and magnesium. That doesn't mean you should stop taking them, but it does mean your medication history matters.
What about SIBO?
Small Intestinal Bacteria Overgrowth (SIBO) is in simple terms an overgrowth of bacteria in the small intestine. Where we really don't want an overgrowth. They can be methane, hydrogen or hydrogen sulphide releasing bacteria and each gas can lead to different symptoms.
Your small intestine has a natural housekeeping mechanism called the migrating motor complex (MMC). Between meals, it helps move residual material and bacteria along the digestive tract.
When intestinal motility is impaired, this clearing process may become less effective. It's one of the reasons slower small intestinal movement can contribute to small intestinal bacterial overgrowth (SIBO) - because bacteria isn't cleared efficiently and small food particles can remain to feed what is there.
SIBO can cause significant bloating, excessive gas, discomfort, extremely smelly gas and changes in bowel habits. Breath testing looks at gases such as hydrogen and methane, which can help us understand different patterns of symptoms, including diarrhoea and constipation. Methane is technically associated with intestinal methanogen overgrowth rather than bacterial overgrowth, but the distinction doesn't need to dominate this discussion.
Interestingly, a 2025 observational study found a higher rate of diagnosed SIBO among people taking GLP-1-based medications. If your symptoms are getting worse, despite all you are doing to help, it's certainly an area worth watching.
If someone is becoming increasingly bloated and constipated, I don't want to automatically tell them to eat more fibre. I want to understand what's happening. Is it simply slower transit, an existing problem that's become worse, or something else that needs investigating?
This is where personalised nutritional therapy can make a real difference. The right advice depends on what's driving the symptoms, not just the symptoms themselves.
Your gallbladder deserves some attention too
This is another aspect of GLP-1 medications that I think deserves much more discussion.
Your liver produces bile, which is stored in your gallbladder and released when you eat, particularly when your meal contains fat. Bile helps you digest and absorb fats, including the fat-soluble vitamins A, D, E and K.
GLP-1 medications may alter how effectively the gallbladder empties, while rapid weight loss itself is a recognised risk factor for gallstones. When bile sits in the gallbladder for longer, crystals can accumulate and form what's known as biliary sludge, which can sometimes develop into gallstones.
Why is this important? A large review of 76 clinical trials involving more than 103,000 participants found that GLP-1 medications were associated with a 37% higher relative risk of gallbladder or biliary disease. The association was stronger in weight-loss trials, although the absolute increase in risk was relatively small.
That doesn't mean everyone taking these medications will develop gallbladder problems. It also doesn't prove that they directly cause biliary sludge. But it's something I would want to consider, particularly if someone already had a history of gallstones or was developing new digestive symptoms.
Bile also does more than digest fat. It helps us absorb those vital nutrients above through it's actions on fat. Bile acids help regulate the intestinal microbial environment and play a role in blood sugar and fat metabolism, which makes this an interesting area of digestive health.
In short, it's really, really important.
If you're experiencing persistent upper abdominal pain, particularly on the right side, perhaps radiating to your back, or nausea and discomfort after eating, don't assume it's simply another side effect of your medication. Gallbladder problems need medical assessment, and severe pain, fever or jaundice requires urgent attention.
Eating less is one thing. Getting enough nutrients is another.
This is one of my biggest concerns when someone is losing weight quickly, particularly if they're experiencing nausea or have very little appetite.
If you're eating half as much as you used to, are you still getting enough protein, iron, calcium, B vitamins, essential fatty acids and other nutrients? And be honest, were you before you started the medications?
You might be losing weight successfully but also eating such a limited range of foods that your nutritional intake is suffering.
And if you were already low in certain nutrients before starting treatment, there's a risk that eating less could make matters worse.
What nutritional problems might develop?
Iron, vitamin B12 and folate are important for healthy red blood cells, energy production and nervous system function. Inadequate intake can contribute to fatigue, poor concentration and, in some cases, anaemia. If someone is already exhausted, I'd want to understand whether they're simply eating too little or whether there's a nutritional deficiency or another medical reason.
Calcium, vitamin D and protein are particularly important for bone and muscle health. These deserve extra attention during midlife, when women are already experiencing hormonal changes that can affect bone density and body composition.
Essential fats matter too, not only for general health but because they provide nutrients that we can't make ourselves. A diet that becomes extremely low in fat or restricted to a handful of foods may be missing more than people realise.
Hydration is another surprisingly easy thing to overlook. Some people report feeling less thirsty while taking these medications, while others simply drink less because they're eating less. Add nausea, vomiting or diarrhoea and dehydration can become a real problem, potentially worsening constipation, headaches, dizziness, fatigue and low blood pressure.
It's important to distinguish between eating fewer nutrients and absorbing them poorly. GLP-1 medications don't automatically cause malabsorption. However, reduced food intake, existing digestive conditions and certain medications can all affect nutritional status.
This is why I don't believe the answer is simply to hand everyone a multivitamin. I prefer to look at what someone is actually eating, their medical history, their symptoms and whether blood testing would help us identify any gaps.
Sometimes a few targeted changes to meals make an enormous difference. Sometimes we need to investigate further. And sometimes a supplement is appropriate, but I'd rather know why we're using it.
Women in midlife: please think about your muscle and bones
Many women are starting these medications during their forties and fifties, just as perimenopause and menopause are making it harder to maintain muscle and protect bone density.
Falling oestrogen can contribute to changes in body composition, including more fat around the middle, while ageing and inactivity can make muscle loss more likely. Now add substantial weight loss into the equation.
Research suggests that around a quarter to two-fifths of weight lost during GLP-1 treatment may be measured as lean mass. Lean mass isn't the same as muscle alone, as it includes water, organs and other tissues, but preserving muscle is still a very important consideration.
Muscle isn't just about looking toned. It helps regulate blood sugar, supports metabolic health and keeps you strong and independent as you age. And your bones need attention too, particularly when weight loss reduces the mechanical loading that helps maintain bone strength.
This is why I'd encourage women to think beyond the scales. Are you getting enough protein? Are you doing anything to maintain your strength? What about calcium, vitamin D and weight-bearing activity?
You don't have to become a gym enthusiast overnight. Small, achievable changes can build strength and confidence, and the right approach will depend on your starting point, health and energy levels.
There's also an important consideration around HRT. Women taking oral HRT should discuss unexpected bleeding or absorption concerns with their prescriber. These aren't reasons to panic, but they are reasons to make sure your prescribing clinician knows what other medications you're taking.
What happens when the weight comes back?
Here's something I think we should be talking about much more: it's not just how much weight you lose, but what you're losing and what happens when the weight comes back.
In the STEP 1 extension study, people who stopped semaglutide regained approximately two-thirds of the weight they'd lost over the following year. That's a substantial amount, but perhaps more concerning is what might happen to body composition.
When you lose weight, you don't just lose fat. You can also lose muscle, and substantial weight loss may affect bone density. When weight comes back, there's no guarantee you'll regain muscle in the same proportion. You could end up with more body fat relative to muscle than you had before, potentially leaving you in a less favourable metabolic position.
For women in perimenopause and menopause, this is particularly important. We're already at a stage of life when maintaining muscle becomes harder and declining oestrogen increases the risk of bone loss. We really don't want to lose muscle and bone while losing weight, only to regain the fat afterwards. This isn't inevitable, but it's a risk worth taking seriously.
And weight regain isn't simply about willpower. After weight loss, our bodies respond by increasing hunger and conserving energy. When medication stops, those biological pressures can become much more noticeable.
Whether you continue or stop, surely it makes sense to use this time to look after your health as well as your weight?
So how can nutritional therapy help?
For the past four years, I've worked with clients taking weight-loss jabs, and with people using earlier treatments before that. Remember Orlistat?
I've also worked with plenty of clients who want to see what they can achieve through nutrition and lifestyle changes before considering GLP-1 medication. Others are already taking it and want to make sure they're staying healthy, managing digestive symptoms, protecting muscle and preparing for the future.
Both approaches are valid, and both deserve individualised support.
As a Registered Nutritional Therapist, I look at your health as a whole. Not just how much weight you've lost, but how you're feeling, what you're eating, how your digestion is functioning and whether you're getting the nutrients your body needs.
Depending on your circumstances, here's what we might work on together:
Your digestive health: understanding whether constipation, reflux, bloating or other symptoms were present before treatment, and whether further investigation, such as SIBO testing, would be appropriate.
Your nutritional status: reviewing your diet and existing blood results, identifying possible deficiencies and considering targeted testing where useful.
Your muscle and bone health: helping you get enough protein, calcium and other important nutrients while developing realistic ways to maintain strength.
Your blood sugar and metabolic health: looking at the bigger picture, including meal composition, fibre, healthy fats and sustainable eating habits.
Your longer-term plan: building routines that support your health whether you remain on medication or eventually stop.
And importantly, I'm not going to give you a list of foods to eat and send you on your way. I want to understand what's going on in your body and why, so we can work out what will actually help you.
Sometimes that means making straightforward changes to what and when you eat.
Sometimes it means addressing constipation before adding more fibre, reviewing your protein intake or looking more closely at a possible nutritional deficiency. And sometimes it means referring you back to your GP or prescribing clinician because something needs medical investigation.
The aim isn't just to lose weight. It's to come through the process as healthy and strong as possible, with habits you can carry forward.
What are you going to take home from the party?
Remember what I said at the beginning? What you bring to the party is what you get at the party.
Well, I'd add something else. What are you going to take home from the party?
Hopefully, it's not just a smaller dress size. It's a better understanding of your body, healthier eating habits, stronger muscles, better blood sugar regulation and the confidence to look after your health for years to come.
And if you arrived at the party with digestive problems, nutritional deficiencies or other health concerns, wouldn't it be lovely to leave having addressed some of those too?
That's what I'd like to help you achieve. Whether you're considering weight-loss medication, already taking it or thinking about life afterwards, let's make sure you're getting more from the experience than simply losing weight.
We can talk through your current health, your concerns and what you're hoping to achieve. I'll explain how I would work with you, and there's absolutely no pressure to book a programme. In fact, I encourage you to go away and think about it. It has to feel right for both of us.
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"Working with Gemma was life changing. She was able to pin point why I was feeling the way I was feeling and helped me manage all the issues with nutrition. I was able feel so much better and actually get out of bed without feeling fatigued. She planned every session considering everything I said to her and always dealing with the main problem. She listened and gave me a encouragement in every session. Gemma explained everything and I learned so much to build healthier habits. This was the best investment into myself and I could not have done this without Gemma's guidance."
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