Optimising GLP-1 therapy – The critical role of lifestyle

Dr Linia Patel gives an evidence-based evaluation of weight-loss drugs and assesses optimising GLP-1 therapy and the critical role of lifestyle

This article is in latest fitpro Magazine (Sep-Oct 2025) which is usually reserved for FitPro members. As part of our commitment to the fitness community, we decided to make it available to all, to give fitness professionals the quality information they need, in this fast-moving and crucial-to-understand field.

Back in 2021, a high-profile client asked if I could support her with Ozempic – then still relatively new but gaining traction in her circle. I set out to give her an evidence-based approach. I never imagined how quickly these weight-loss jabs would go mainstream. Fast forward to last week: in my women’s health clinic, every single woman struggling with her weight asked me about them.

The weighty challenge we can’t ignore^1,2,3,4

Let’s be real: obesity isn’t just a personal struggle – it’s a public health crisis. In the US, over 40% of adults are living with obesity¹. In the UK, we’re not far behind. According to the most recent National Diet and Nutrition Survey, 28% of men and 29% of women fall into the obesity category. That’s nearly one in three adults².

The ripple effects are massive. Obesity is linked to an increased risk of type II diabetes, heart disease, joint issues and certain cancers – not to mention the psychological toll it can take. The cost to healthcare systems is soaring. In the UK, obesity-related conditions are estimated to cost the NHS billions each year^2,3,4.

So, it’s no surprise weight-loss injections (originally developed to treat type II diabetes) exploded in popularity when people noticed their appetite-suppressing superpower^1,3,4,5. One in eight Americans is now thought to have used a GLP-1 drug¹. In the UK, newly updated National Institute of Clinical Excellence (NICE) guidelines mean that roughly 3.4 million people are eligible to receive these medications on the NHS^1,5.

GLP-1: What it is^1,6

GLP-1 isn’t some new pharmaceutical invention. It’s a naturally occurring hormone our bodies have had all along – a part of the incretin family, produced in the gut and brain. Its job? Helping us feel full and satisfied after a meal. However, for people living with obesity, this system doesn’t always work the way it should. Some may produce less GLP-1 or break it down more rapidly. Others may have issues with how their body responds to the hormone, due to long-standing insulin resistance, gut microbiome imbalances or even genetics. The result? It can feel harder – sometimes impossibly hard – to know when you’re full or to quiet the constant ‘food noise’.

Whether naturally produced or synthetically mimicked, GLP-1 plays a central role in appetite regulation. Enter GLP-1 medications like semaglutide (Ozempic, Wegovy), liraglutide (Saxenda) and tirzepatide (Mounjaro), which mimic this hormone’s natural function. These drugs work by:

• slowing digestion(so you feel full for longer)
• reducing food cravings and ‘food noise’in the brain
• boosting insulin release, which helps manage blood sugar and increases satiety.

Mounjaro goes one step further by also mimicking another hormone – GIP (gastric inhibitory polypeptide) – which amplifies these effects by further slowing digestion and enhancing the body’s insulin response.

Do they work?^{1,6,7,8,9,10,11,12}

Short answer: yes, they work. In fact, GLP-1 medications are the most effective pharmaceutical weight-loss tools we’ve ever had. Compared to traditional lifestyle interventions, these drugs offer exponentially greater outcomes. For years, the gold standard in obesity treatment was bariatric surgery – effective but invasive, costly and not without risk. Now, for the first time, medications are approaching that level of effectiveness, without the surgery.

In the STEP 1 trial, participants who received 2.4mg of semaglutide weekly lost an average of 14.9% of their bodyweight over 68 weeks. The placebo group? Just 2.4%. Other studies show that around one third of people taking GLP-1 medications like Ozempic or Wegovy lose more than 20% of their bodyweight – a result once thought only achievable with surgery⁸.

“Up to 39-40% of the total weight lost with GLP-1 drugs may come from lean body mass”

When paired with a balanced diet and regular exercise, Wegovy has been shown to support average weight loss of nearly 15% in a year. Mounjaro (tirzepatide), part of the next generation of GLP-1 + GIP medications, has raised the bar further, with average weight loss hovering around 17%, and 57% of users losing more than 20% of their bodyweight⁹. Even on a public health scale, we’re seeing an impact. In the US, for the first time in years, obesity rates appear to have stalled¹¹.

But let’s be clear: there is no such thing as a magic jab. These drugs are powerful, yes. But they’re only one piece of the puzzle.

Firstly, as fit pros, you know well that sustainable weight loss isn’t just about the number on the scale – it’s about losing the right kind of weight while supporting overall health. This is where things get tricky. One of the major concerns emerging from clinical trials is muscle loss. Post-hoc analyses from the STEP trials suggest up to 39-40% of the total weight lost with GLP-1 drugs may come from lean body mass, including skeletal muscle¹¹. That number jumps higher among people who aren’t resistance training or consuming enough dietary protein. Lose too much muscle and you risk slowing your metabolism, compromising strength and increasing your chances of weight regain.

In a follow-up study of 300 participants one year after stopping semaglutide, two thirds of the weight lost was regained. What’s more concerning is how that weight came back. In a study of postmenopausal women, 88% of the regained weight was fat, while only 12% was lean mass¹². That kind of rebound not only impacts appearance but has real implications for cardiovascular health, strength, insulin sensitivity and long-term quality of life.

The health benefits beyond the scale^{13,14,15,16,17}

When I worked on the ground in obesity services as a dietitian – and later, when I moved into a strategic role commissioning obesity programmes – a familiar refrain was used: “Losing 5-10% of your bodyweight can make a real difference.”

And it was true. Those early guidelines weren’t just about setting realistic goals – they were backed by science. Modest weight loss of 5-10% has been shown to improve cholesterol, lower blood pressure and stabilise blood sugar⁴. Small steps, big wins. But we’re now entering a new era, where weight loss in the range of 15-20% is not only achievable, but potentially life changing.

Shedding 15-20% of bodyweight can lead to remission of chronic conditions like type II diabetes, high blood pressure, fatty liver disease and even obstructive sleep apnoea. A standout example is the SELECT trial, which studied semaglutide in people with established cardiovascular risk. The results? A 20% reduction in major cardiovascular events like heart attacks and strokes. Off the back of this data, semaglutide is now licensed in the US, Canada and the UK, not just for weight management but also as a treatment for cardiovascular disease.

New research is emerging on a near-daily basis, exploring GLP-1 medications for conditions like:

• polycystic ovarian syndrome (PCOS)
• addiction(including smoking, alcohol and recreational drug use)
• cognitive health and dementia
• obesity-related cancers, such as breast and colon cancer.

Common side effects^1,6

More than half of users experience side effects but, for most, they’re mild, manageable and tend to improve over time, especially when supported with the right nutrition and lifestyle changes.

Here are some of the most common side effects I see in practice:

• Egg burps– About one in 10 people get sulphuric, eggy-smelling burps due to changes in gut bacteria and slowed digestion. It’s not dangerous, just unpleasant.
• Constipation– With digestion slowed down and fibre often low (especially in the early days of reduced appetite), constipation is a frequent complaint.
• Nausea– This is particularly common at higher doses or when meals are skipped or too heavy. Poor nutrition tends to make this worse.
• ‘Ozempic face’ or ‘Ozempic butt’– A term used to describe the loss of volume in the face and glutes due to muscle and fat loss, especially with rapid weight loss and inadequate strength training.
• Weight-loss addiction– The dramatic changes can be intoxicating and some people push too far, too fast, leading to over-restriction, over-training or disordered eating patterns.
• Gallstones– Rapid weight loss can increase the risk of gallstone formation, a side effect seen in other fast weight-loss methods.
• Pancreatitis– Rare (affecting fewer than one in 500) but serious. Anyone experiencing severe abdominal pain should seek urgent medical attention.

And while we’re still learning, there are some unanswered questions. To date, there are very few trials measuring bone mineral density during GLP-1-induced weight loss. We know that both fat and muscle are lost, but what about bone? It’s a critical gap in our understanding, particularly for women in midlife and beyond.

Why nutrition and lifestyle still matter^5,6,18,19,20

Powerful weight-loss medications like GLP-1s don’t replace lifestyle – they make it more essential than ever. While these drugs can kickstart weight loss, it’s nutrition, movement and mindset that determine whether the results are safe, sustainable and protective long term.

Up to 30-40% of the weight lost on GLP-1s can come from lean mass, including muscle¹⁸. Without resistance training and adequate protein, this can slow metabolism and impair physical function. Lifestyle habits also protect against weight regain – common after stopping medication if no behavioural changes are in place¹⁹. Beyond weight, diet and exercise lower inflammation, improve insulin sensitivity and reduce disease risk. Medications can shift the scale but only lifestyle builds lasting health.

“People would prefer to lose weight without using medications”

We also eat for more reasons than being physically hungry. GLP-1s help with physical hunger but they don’t touch emotional, habitual or environmental triggers. That’s where lifestyle coaching steps in. Lifestyle interventions, such as mindful eating and stress management, help build resilience and long-term self-regulation.

Despite all the hype, what’s intriguing is the public hasn’t completely bought into the medication-first model. In a December 2024 Ipsos survey of over 2,000 UK adults, people still say they would prefer to lose weight without using medications. Here are the findings²⁰:

• 6% said they intended to lose weight through more exercise.
• 42% planned to eat healthier.
• Only 3% were considering weight-loss injections.
• Even if offered free on the NHS, only 24% said they’d take them.
• That figure dropped to 7% if they had to pay privately.

So, while weight-loss meds are powerful tools, they’re not the whole solution – and they’re not the preferred solution for most people (based on survey).

Eight strategies to make weight-loss medications more effective^6,21,22,23

1. Eat – even if you don’t feel like it

GLP-1 medications suppress appetite quickly and dramatically but not eating is not the goal. Skipping meals can worsen side effects like nausea and constipation, and lead to unhealthy, muscle-heavy weight loss. Start with small, nutrient-dense meals:

• Smoothies with fruit, protein and nut butter
• Pureed soups with beans and lentils
• Wholegrain crackers with cheese
• Yogurt with seeds and berries

If your intake is very low, consider a food-state multivitamin for extra support. Staying nourished helps you feel better and lose the right kind of weight.

2. Prioritise protein

Protein not only stimulates natural GLP-1 but it preserves muscle mass during weight loss and keeps you feeling fuller for longer. Aim for at least 70g of protein per day. Include protein at every meal – think eggs, yogurt, tofu, lentils, fish or poultry. Combine this with at least two full-body resistance training sessions per week to maintain muscle and metabolism. Just moving more (e.g., daily walks) helps preserve lean tissue too.

3. Fill up on fibre

Fibre supports gut health, blood sugar control and – you guessed it – GLP-1 production. When fibre ferments in the gut, it produces short-chain fatty acids like butyrate, which stimulate GLP-1 release.

• Swap white refined carbs for wholegrains, beans, lentils.
• Load up on colourful fruits and veg.
• Add seeds, oats and legumes for an extra fibre boost.

Tip: Soluble fibre (found in oats, flaxseeds, apples) is especially beneficial for feeding your gut bacteria and improving GLP-1 activity.

4. Choose healthy fats

Not all fats are created equal. While saturated fats (like butter) may dull GLP-1 signalling, healthy fats do the opposite. They are linked to improved satiety, hormone function and stronger GLP-1 responses. They also deliver key nutrients like vitamins A, D, E and K. Choose:

• avocados
• nuts (almonds, pistachios, peanuts)
• extra virgin olive oil
• oily fish.

5. Nourish your gut bacteria

A healthy microbiome = better GLP-1 function. Fermentable fibres (like those in legumes, leeks and oats) feed your gut bugs, especially bifidobacteria, which help produce those short-chain fatty acids that stimulate GLP-1. You can also consider probiotics – some strains, like Bifidobacterium adolescentis, may support this pathway. But focus on food first: prebiotics (plant fibre) are what your gut flora needs to thrive.

6. Prioritise strength training

Exercise isn’t just about burning calories – it preserves muscle mass, improves insulin sensitivity, boosts mood and naturally increases GLP-1 levels. When it comes to movement, walking is a powerful place to begin. Over time, add strength training for metabolic support.

7. Get more sleep, consistently

Sleep and hormone regulation go hand in hand. While one bad night won’t wreck your progress, chronic sleep deprivation will. Studies show that getting only four hours of sleep for a few nights in a row can impair GLP-1 function and increase cravings for sugar and processed foods. Aim for seven to eight hours. Prioritise wind-down rituals and:

• limit screens
• dim lights
• try magnesium or meditation if needed.

8. Mindset makes the difference

Lifestyle change isn’t just about habits – it’s about headspace. GLP-1s regulate hunger but they don’t address emotional eating, stress eating or food beliefs. That’s where support really matters. It’s important that a health professional works with you on your journey. Consider also working with a coach or therapist or joining a support group.

What comes next?

This is a fast-moving space and we’re still learning. New research continues to shape how we think about GLP-1 medications and long-term weight management. One big question remains: how long should people stay on them? Some experts suggest lifelong use, others see a phased, on-and-off approach. We’re also seeing hybrid models emerge, combining medication with coaching, nutrition, exercise and mental health support. However, access is unequal and that inequity raises serious public health concerns. What we do know is this: whether someone takes GLP-1s for months or years, how they support their body and mind – through nourishment, movement, habit change and emotional resilience – will shape their long-term success.

Read more of Dr Linia Patel’s expertise, this blog on or choose from her 7 nutrition based courses on the FitPro education platform.

REFERENCES

1. Tony Blair Institute for Global Change. Unhealthy Numbers: The Rising Cost of Obesity in the UK. London: Tony Blair Institute; 2023. Available from: https://www.institute.global/insights/public-services/unhealthy-numbers-the-rising-cost-of-obesity-in-the-uk
2. Department of Health and Social Care. National Diet and Nutrition Survey: Years 12 to 15 (2019 to 2023). London: DHSC; 2024. Available from: https://www.gov.uk/government/statistics/national-diet-and-nutrition-survey-2019-to-2023
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5. British Dietetic Association, British Nutrition Foundation. Joint policy statement regarding GLP-1/GIP receptor agonists in people living with obesity and/or type 2 diabetes. Birmingham: BDA; 2024 Mar. Available from: https://www.bda.uk.com/resource/joint-policy-statement-regarding-glp-1-gip-receptor-agonists-in-people-living-with-obesity-and-or-type-2-diabetes.html
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