Abstract
Background: GLP-1 receptor agonists (GLP-1 RAs) are prescribed for type 2 diabetes, weight management and cardiovascular risk reduction in individuals where a BMI of 27 kg/m² or more is accompanied by comorbidities. The appetite suppressing effect of this class of medications may compromise nutritional adequacy. Evidence on dietary intake in GLP-1 RA users remains limited, with no studies published on UK population to date. This is the first UK focused cross-sectional observational study to assess macro- and micronutrient intake in UK adults using GLP-1 RAs and compare findings against UK DRVs.
Methods: The study was conducted among adult GLP-1 RA users (n=38, mean age 51.6 ± 8.2 years; 86.8% female). The participants completed a questionnaire on anthropometric data and GLP-1 usage. They also recorded 3-day food diaries using INTAKE24, an online tool. Nutrient intakes were analysed against UK DRVs.
Results: Mean daily energy intake was 1,337 ± 475 kcal/day. 89.5% of participants did not meet their estimated average requirement (EAR). All participants (100%) fell below the fibre DRV of 30 g/day, with a mean intake of 14.5 ± 4.9 g/day. Nearly half (44.7%) fell short of the protein EAR of 0.75 g/kg/day. Widespread micronutrient inadequacy was observed. Vitamin D, potassium and selenium showed the most severe deficit, with greater than 90% of participants below the RNI. 81.6% were below the RNI for iron and 78.9% for magnesium. Although 73.7% of participants reported taking supplements, supplementation appeared largely unsupervised, with fewer than 10% under professional nutritional guidance.
Conclusions: UK adults using GLP-1 RAs demonstrate widespread shortfalls across both macro- and micronutrients relative to UK DRVs and energy intake. While supplementation partially addressed some deficits, its use was largely ad hoc. These findings highlight the need for structured, evidence-based nutritional support to be integrated into GLP-1 RA prescribing pathways in the UK.
1. Do GLP-1 medications cause nutrient deficiencies?
GLP-1 receptor agonists don’t directly block nutrient absorption — they may cause deficiencies indirectly, by sharply reducing how much food people eat. In this UK study, participants consumed only 1,337 kcal/day on average, about 345 kcal/day less than typical UK adults, and 89.5% fell short of their estimated energy needs. Lower food intake naturally pulls down intake of fibre, protein, and several vitamins and minerals.
2. What vitamins and minerals are most at risk for people on GLP-1 drugs like Ozempic, Wegovy, Mounjaro, or Zepbound?
Over 90% of participants fell below the UK Reference Nutrient Intake (RNI) for each. Iron was low in 81.6%, and magnesium in 78.9%. Folate and vitamin A were inadequate in 63.2%, and vitamin B6 in 52.6%. By contrast, vitamin B12 and vitamin E were well maintained in most participants.
3. Do people on GLP-1 medications get enough fibre?
No — in this study, 100% of participants fell below the UK fibre target of 30g/day, with a mean intake of just 14.5g/day, less than half the recommendation. Interestingly, this matches both a comparable US study (also 14.5g/day) and the general UK population average (16.4g/day), suggesting low fibre intake is a pre-existing population pattern that GLP-1 use doesn’t make meaningfully worse — but it does compound the constipation that’s already common with these drugs (76.3% of participants reported it).
4. Is nutrient deficiency on GLP-1 medications caused by the drug itself, or by pre-existing UK dietary patterns?
Both, but the contribution differs by nutrient. Comparing this cohort to UK national diet data (NDNS 2019–2023), shortfalls in fibre, iron, vitamin D, and selenium reflect pre-existing population-wide dietary patterns rather than a GLP-1-specific effect. However, magnesium and potassium inadequacy was worse than the general population, suggesting GLP-1 use may specifically worsen intake of those two nutrients.
5. Is this the first UK study on GLP-1 medication and nutrient intake?
To the author’s knowledge, yes. This is the first UK-based cross-sectional study to assess macro- and micronutrient intake among GLP-1 RA users using validated 3-day food diaries, comparing results directly against UK Dietary Reference Values rather than relying on US-based data or extrapolating from bariatric surgery research.
6. Should you see a Registered Nutritionist while taking GLP-1 weight-loss medication
The evidence increasingly says yes. This study, along with expert consensus guidance and dietitian surveys, points to structured nutritional support being needed alongside GLP-1 prescribing — not just generic advice on managing nausea, but active monitoring of protein, fibre, and micronutrient intake, since most users currently manage supplementation on their own without guidance.
