8 minute read

In this article:

• The GLP-1 bandwagon — and why nutrition matters more, not less
• A word before we begin
• 1. Protein — the non-negotiable
• 2. Fibre — just as important as protein
• 3. Nutrient density — what goes into smaller meals matters more
• 4. Hydration — more important than you think
• 5. Key nutrients to monitor — and what to do about them
• 6. Healthy fats — why fat is not the enemy
• A note on supplements while on GLP-1 medications

The GLP-1 bandwagon — and why nutrition matters more, not less

GLP-1 receptor agonists - medications including semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) have transformed the treatment landscape for obesity and metabolic health. The clinical evidence for their effectiveness in achieving meaningful weight loss is strong, and their benefits extend beyond weight alone, with emerging evidence for cardiovascular, hepatic, and renal outcomes.

They have also triggered significant shifts to the food industry and are impacting everything from fashion to travel. As author Johann Hari, who spent a year researching GLP-1 medications for his 2024 book Magic Pill, put it on The Diary of a CEO:

Whilst results are undeniable, the research in this area is still evolving rapidly. What is clear is that these medications have entered widespread use faster than the clinical evidence on their long-term nutritional implications can keep up with - and there is currently a significant amount of unregistered and unmonitored use that means we simply do not yet have population-level data at the scale we need. Much of what is being marketed around GLP-1 medications - from specialist supplement ranges to specific dietary protocols - is running well ahead of the science.

What the evidence does show clearly is this: when you are on a GLP-1 medication and eating significantly less, nutrition does not matter less - it matters considerably more. If the quantity of food goes down, the nutritional quality of what remains needs to go up. Getting that balance right is one of the most important and least discussed aspects of using these medications well.

A word before we begin

GLP-1 medications are serious pharmaceutical drugs. They were developed in a clinical setting for the treatment of type 2 diabetes and obesity, and when used appropriately - under medical supervision, for the right reasons, with careful monitoring - they can be life-changing for people who need them.

What concerns us as a nutrition brand is the growing culture of casual, unsupervised use for those who don't qualify to take these drugs from a medical standpoint. Whilst many in need of the drugs may struggle to get hold of them on the NHS in the UK, GLP-1s are not lifestyle drugs to be started lightly, stop-started sourced online, or used without a doctor's ongoing involvement. Stories of sharing pens between households and taking random doses without proper advice are rampant and concerning. Whilst weight loss is at the heart of why many take these drugs, others are pressured by other purported (but as yet unproven) benefits on wellbeing.

Whatever the route, the side effects of taking these drugs can be significant and the nutritional risks, as this article explains, are real. These can escalate to serious malnutrition if not properly managed and this is something many experts report seeing in their clinics. Stopping the medication without a plan frequently leads to rapid weight regain - because the underlying dietary and lifestyle foundations have not been built alongside. Cambridge professor and obesity scientist Dr Giles Yeo explains it how it is:

If you are considering GLP-1 medication, please do so with your GP or a specialist physician who can assess whether it is appropriate for you, monitor your health throughout, and support you with the dietary and lifestyle changes that make these medications work safely and sustainably. If you are already taking one, this article is designed to help you protect your health while you do.

Approached properly - with medical oversight, nutritional awareness, and an active commitment to diet and exercise - GLP-1 medications can be a powerful tool. Approached casually, they carry risks that are not yet fully understood, and that deserve to be taken seriously.

Here is what the evidence currently supports and what our nutritionists recommend:

1. Protein — the non-negotiable

One of the most consistent findings from GLP-1 clinical trials is that weight loss includes a meaningful proportion of lean muscle mass alongside fat. Studies have shown that while GLP-1 receptor agonists are effective in reducing fat mass, up to 40% of the total weight loss can come from fat-free mass.¹ Whilst typical weight loss diets also lead to muscle loss, the magnitude of this lean tissue loss with GLP-1s has been likened to that typically accrued over a decade or more of ageing.

To protect yourself against this, the first thing to be aware of is that protein intake and physical activity need to be taken extremely seriously. A prospective six-month study of 200 adults who received education on resistance training and protein intake at the time of starting semaglutide or tirzepatide found that participants lost approximately 13% of their body weight but only around 3% of their muscle mass - significantly less than trials where no such guidance was given.² Resistance training and remaining as active as possible alongside GLP-1 therapy is a core part of using these medications well and staying healthy.

Protein intake is equally central. When calorie intake falls significantly, the body is at greater risk of drawing on muscle tissue for energy - particularly if protein intake is insufficient. For individuals actively losing weight with GLP-1s many experts recommend 1.2 to 1.6 grams of protein per kilogram of body weight per day.³ For a woman weighing 75kg, that means 90–120g of protein daily. We aren't usually ones for counting our macro's but when you begin these medications, and appetite is significantly suppressed and meal volumes are small, some deliberate planning is wise.

Good protein sources that work well in smaller meals:

• Greek yoghurt (200g) - approximately 20g protein
• Cottage cheese (150g) - approximately 18g protein
• 2 eggs - approximately 12g protein
• Cod fillet (150g) - approximately 33g protein, very lean and easy to digest
• Chicken breast (150g) - approximately 45g protein
• Tofu (150g) - approximately 12g protein
• Edamame (100g) - approximately 11g protein
• Kefir (250ml) - approximately 8g protein alongside gut-supporting probiotics
• Lentils or chickpeas (100g cooked) - approximately 9g protein, also provide fibre
• Mixed nuts (30g) - approximately 7g protein alongside healthy fats

Plant-based protein sources such as lentils, beans, tofu, and edamame are particularly efficient because they also contribute fibre - something especially valuable when eating less overall.

2. Fibre — just as important as protein

The UK recommendation for dietary fibre is 30g per day - a target most people do not hit even on a normal diet. When overall food volume falls significantly on GLP-1 medications, fibre intake often falls with it at exactly the point it matters most.

GLP-1 medications already slow gastric emptying as part of their mechanism. When fibre intake also falls, constipation (one of the most commonly reported side effects of these medications) becomes more likely and sometimes, more uncomfortable. Fibre also feeds the gut microbiome, and on a reduced calorie intake, maintaining gut microbial diversity requires deliberate attention to plant variety even in small quantities.

If you are not used to eating 30g of fibre per day, increasing too quickly can cause bloating and discomfort - particularly when the digestive system is already slowing. Build up gradually, adding one or two fibre-rich foods at a time over several weeks, and drink plenty of water alongside. The goal is to find easy wins at every meal rather than one large fibre hit at the end of the day.

Easy ways to build fibre into every meal:

• Raspberries (100g) — approximately 6g of fibre, one of the highest per calorie of any fruit. Easy to add to yoghurt or eat as a snack
• Chia seeds (2 tablespoons) — approximately 8g of fibre. Stir into yoghurt, water, or a small smoothie. Ensure fully soaked first (20 mins)
• Ground flaxseed (1 tablespoon) — approximately 3g of fibre plus omega-3 fatty acids. Add to anything but again, best soaked or consumed with water, as they absorb water from the bowel.
• Broccoli (100g) — approximately 3g of fibre, dense in vitamins and minerals
• Lentils or chickpeas (100g cooked) — approximately 8g of fibre and also a protein source
• Avocado (half) — approximately 5g of fibre alongside healthy fats
• Leafy greens — lower in fibre per gram but easy to include in volume
• Sweet potato

Your plant-based proteins double up as fibre sources - tahini, lentils, beans, edamame, and tofu all contribute to both goals simultaneously, making them particularly efficient choices when eating less.

3. Nutrient density — what goes into smaller meals matters more

When you are only eating two small meals a day, those meals cannot afford to be nutrient-poor. This is perhaps the most important principle, and the one most at odds with how many people actually eat when nausea or reduced appetite makes plain, simple food the path of least resistance.

GLP-1 side effects including nausea, bloating, and slow digestion are reasons to be thoughtful about what goes into smaller meals. Ultra-processed foods and drinks high in additives, emulsifiers, and refined ingredients can be harder for a slowed digestive system to process, and they displace the protein, fibre, and micronutrients the body needs. A small meal of Greek yoghurt with berries, seeds, and a drizzle of olive oil delivers significantly more than the same calorie count from crackers or toast. They also tend to lead to fewer gastro related side effects.

Smaller meals, more frequently, generally work better than two large meals - both for digestive comfort and for maintaining stable blood sugar and energy throughout the day.

4. Hydration — more important than you think

We know you've heard it before, but bear with us because this one is boring but important! GLP-1 receptor agonists have been shown to suppress water intake independent of their effects on food intake, meaning appetite suppression can reduce fluid consumption as well as food volume. When food intake falls, an additional source of hydration disappears too, since a meaningful proportion of daily fluid intake comes from food.

Constipation is worsened significantly by inadequate hydration. So is the risk of headaches, low energy, and poor cognitive performance. Starting the day with a glass of water before anything else is a simple habit that matters more than usual when appetite is suppressed.

Target at least 1.5–2 litres of water or herbal tea per day. Quality electrolyte drinks without too much sugar or sweeteners can help if constipation or headaches are present. If plain water feels unappealing, warm water with lemon or herbal teas are just as effective.

5. Key nutrients to monitor — and what to do about them

A 2026 narrative review encompassing 480,825 adults found that GLP-1 receptor agonists may predispose users to micronutrient deficiencies through appetite suppression, delayed gastric emptying, and altered absorption.⁴ Vitamin D deficiency was the most common finding, occurring in 7.5% at 6 months and 13.6% at 12 months. Iron depletion was frequent, with GLP-1 users demonstrating a 26% higher rate of iron deficiency compared to controls.

It is also worth acknowledging that the data here is still developing. Given the scale of unregistered and unsupervised GLP-1 use (particularly in the UK) we do not yet have the population-level nutritional monitoring data at the depth needed to draw firm conclusions. What we do know is that the mechanisms for deficiency are clear and the early evidence is consistent enough to take seriously.

The nutrients most worth monitoring:

• Iron and ferritin - iron deficiency is already one of the most common causes of fatigue in women, and the risk increases on GLP-1 medications. Prospective data suggest semaglutide may reduce intestinal iron absorption directly, in addition to the reduction in dietary iron from eating less. Ask your GP for a ferritin test specifically - a result below 50 ng/mL in a menstruating woman experiencing fatigue/hair loss warrants attention even if it sits within the standard reference range. Iron supplements are notorious for making constipation worse, and many women tell us this has worsened their gastro related symptoms. It's therefore vital to choose forms that are easily absorbed, and this also means you can take lower, more efficient, doses. Look for Ferrochel® iron, which is what we use in our new Energy Formula.
• Vitamin B12 - found primarily in animal foods, B12 is increasingly at risk when overall dietary intake is reduced. Deficiency develops slowly but has significant neurological and metabolic consequences. Methyl-cobalamin is the active form the body uses most efficiently, again used in all Equi products including Energy Formula.
• Vitamin D - the most commonly deficient nutrient in UK adults even without GLP-1 medications, and the most consistently flagged in GLP-1 deficiency data. A sensible daily dose of vitamin D3 (around 10–25mcg) is a reasonable precaution for most people, particularly through the autumn and winter months. Always combine with K2 to ensure adequate distribution in the body.
• Zinc - involved in immune function, skin health, hormonal balance, and protein synthesis and also needed for collagen production in skin and joints. Suboptimal zinc is common in people eating a restricted or low-variety diet. Zinc picolinate is the best quality and most absorbable form, used across Equi's range.

We hasten to add here that this does not mean taking high doses of anything. In particular B12 supplements on the market are often formulated at 10,000 times the nutrient reference value and high B12 is commonly see on test results for this reason. Iron supplements are often given at levels that cause significant gastrointestinal side effects (especially when in the form ferrous sulphate) and iron overload can occur in those who don't need it, with negative consequences. High-dose vitamin D without adequate vitamin K2 and magnesium can also create imbalances rather than correct them.

The most sensible approach is a broad-spectrum formula providing these nutrients at clinically appropriate, gentle, safe doses in their most bioavailable forms - enough to fill the gaps created by eating less, without the risk of overcorrection. Energy Formula provides iron as Ferrochel® iron bisglycinate at a gentle 7mg dose, a complex of B vitamins in their active methylated forms, vitamin D3/K2, zinc, and a broad micronutrient base, all designed to support nutritional status without any risk of the imbalances that come with high-dose isolated supplementation. It's also got an array of nutrient dense botanicals, superfoods and anti-oxidants such as co-Q10, as well as gentle thyroid and hormone support.

For anyone taking GLP-1 medications, our nutritionist Alice recommends getting a full blood panel done at least once a year - and ideally before you start, so you have a true baseline to track against over time.

Alongside the standard bloods your prescribing doctor should be running, ask specifically for: iron and ferritin, vitamin B12, folate, vitamin D, zinc, and full thyroid function including TSH, free T3, free T4, and thyroid antibodies.

These are the nutrients most likely to be affected during GLP-1 therapy - and the ones most commonly missed on a standard annual check. Knowing where you start means you can identify changes early, supplement intelligently rather than guessing, and have an informed conversation with your GP if something shifts. It also means that if you do experience fatigue, hair changes, low mood, or other symptoms that could point to a nutritional gap, you have the data to act on rather than simply hoping for the best.

6. Healthy fats — why fat is not the enemy

When overall food intake falls and nausea is present, fat is often the first macronutrient to be reduced - sometimes deliberately to manage symptoms and sometimes because rich foods simply do not appeal. But healthy fats are essential for hormone production, fat-soluble vitamin absorption (vitamins A, D, E, and K all require dietary fat to be absorbed), skin health, brain function, and concentration. Without adequate healthy fat, these systems begin to underperform - contributing to the dry skin, difficulty concentrating, and low mood that some women experience during significant weight loss. Sleep can also be impacted.

Evidence from clinical studies also indicates that omega-3 polyunsaturated fatty acids may attenuate lean mass loss during GLP-1 therapy, primarily via anti-inflammatory pathways and modulation of protein synthesis.⁵ Omega-3s are therefore not just a general wellness consideration on these medications - they may actively support the preservation of lean tissue that GLP-1 therapy puts at risk.

Omega-3 food sources to prioritise:

• Oily fish - salmon, mackerel, sardines, herring (2–3 portions per week)
• Ground hempseed, flaxseed and chia seeds - plant-based ALA omega-3 that the body partially converts to EPA and DHA (3-4 times per week)
• Walnuts - a useful everyday source

Other good fats to include:

• Extra virgin olive oil — 1-2 TBSP / day
• Nuts & seeds of all kinds — 1-2 palmfuls per day
• Avocado — ¼ per day
• Tahini — mix 1 TBSP with water, salt and lemon juice and use as a dressing for roasted vegetables or salad leaves

When appetite makes rich oily foods unappealing - as it frequently does on GLP-1 medications - supplementation becomes particularly relevant.

Our Beauty Oil Edition is formulated around krill oil - a highly bioavailable source of EPA and DHA omega-3 fatty acids that support skin health, cardiovascular function, and the anti-inflammatory pathways relevant to lean mass preservation. Krill oil also contains astaxanthin, a powerful antioxidant that provides additional protection against the oxidative stress associated with rapid body composition change.

Omega-7 fatty acids from sea buckthorn oil deserve specific mention in the context of GLP-1 use. As body composition changes rapidly during weight loss, the mucous membranes throughout the body (including the gut lining, vaginal tissue, and skin) can become drier and more vulnerable. Omega-7 fatty acids are a key structural component of these mucosal tissues. A randomised double-blind placebo-controlled trial in postmenopausal women found that oral sea buckthorn oil significantly improved vaginal epithelial integrity compared to placebo.⁶ A 2024 RCT corroborated these findings across vaginal, skin, and ocular health.⁷ Our Menopause Oil Edition is formulated around sea buckthorn oil and is particularly relevant for women in perimenopause or menopause who are also using GLP-1 medications and experiencing mucosal or skin dryness.

A note on supplements while on GLP-1 medications

The supplement market around GLP-1 medications is expanding rapidly - and much of what is being marketed is opportunistic rather than evidence-based. So-called natural GLP-1 boosters are not supported by robust human clinical evidence. Products claiming to replicate or enhance GLP-1 drug effects should be approached with scepticism.

What supplementation can and should do is address the nutritional gaps that GLP-1 medications create - protecting against the deficiencies that develop quietly over months of significantly reduced food volume, at safe and appropriate doses rather than therapeutic mega-doses.

A practical protocol for women on GLP-1 medications, based on current evidence:

• Energy Formula - a comprehensive daily formula covering active B vitamins in methylated forms, iron bisglycinate at a gentle safe dose, zinc, vitamin D3, magnesium bisglycinate, CoQ10 for mitochondrial energy, adaptogenic support, and a broad micronutrient base. Always taken with food.
• Collagen & Keratin Edition - Hydrolysed collagen at a clinical dose alongside vitamin C, zinc, hyaluronic acid, and antioxidants - supporting skin elasticity, connective tissue, and joint health during rapid body composition change.
• Beauty Oil Edition - krill oil providing highly bioavailable omega-3 EPA and DHA for skin, cardiovascular health, and lean mass support.
• Menopause Oil Edition - sea buckthorn oil providing omega-7 fatty acids for mucosal integrity and skin barrier support - particularly relevant for perimenopausal and menopausal women experiencing dryness during weight loss.

None of these are a substitute for the dietary principles above. Food comes first - always. But when eating significantly less, these formulas help ensure the body still has access to what it needs to function, recover, and stay resilient. And none of them replicate or replace the medical supervision that GLP-1 medications require.

Further reading

For anyone who wants to go deeper on the nutritional science behind GLP-1 medications, we recommend The Appetite Reset: How to Eat, Drink and Thrive Before, During and After GLP-1s by Dr Federica Amati. Published in 2025, it is the most thorough and evidence-based guide currently available on eating well at every stage of GLP-1 therapy.

Written by the Equi London nutrition team

This article is for educational purposes only and does not constitute medical advice. GLP-1 medications are prescription drugs that should only be used under the supervision of a qualified medical professional. If you are taking or considering GLP-1 medications, please discuss any dietary changes or supplementation with your prescribing doctor or a registered healthcare professional before making changes. Food supplements should not be used as a substitute for a varied, balanced diet or healthy lifestyle.

References

1. Scheen AJ. GLP-1 receptor agonists, body composition, skeletal muscle and risk of sarcopaenia: from promising findings in animal models to debated concern in human studies. Diabetes Metab. 2025;51(5):101681.
2. Peralta-Reich D, et al. Incretin-based obesity medications show minimal lean muscle mass loss in 6-month prospective study. Abstract presented at: European Congress on Obesity (ECO 2025); May 2025; Malaga, Spain.
3. Christodoulides S, Lam A, McLean A, Lam V, Moran LJ, Lim SS. Nutrition support whilst on glucagon-like peptide-1 based therapy. Is it necessary? Curr Opin Clin Nutr Metab Care. 2025;28(5):397–404. doi:10.1097/MCO.0000000000001100.
4. Urbina EM, et al. Micronutrient and nutritional deficiencies associated with GLP-1 receptor agonist therapy: a narrative review. Clin Obes. 2026;16(1):e70070.
5. Dias DD, Vasconcelos AR, Souza ACR, de Menezes C, Silva IST, Name JJ. Nutritional approaches to enhance GLP-1 analogue therapy in obesity: a narrative review. Obesities. 2025;5(4):88. doi:10.3390/obesities5040088.
6. Larmo PS, Yang B, Hyssälä J, Kallio HP, Erkkola R. Effects of sea buckthorn oil intake on vaginal atrophy in postmenopausal women: a randomized, double-blind, placebo-controlled study. Maturitas. 2014;79(3):316–321.
7. Chan E, Garzon C, Grice DM, et al. The impact of oral sea-buckthorn oil on skin, blood markers, ocular, and vaginal health: a randomized controlled trial. J Funct Foods. 2024;112:105973.
8. Amati F. The Appetite Reset: How to Eat, Drink and Thrive Before, During and After GLP-1s. London: Penguin; 2025.