New study: 1 in 5 GLP-1 users develop nutritional deficiencies
This week, I'm unpacking a brand new study by Butsch et al. (2025) that reveals just how common nutritional deficiencies are with GLP-1 medications and what you can do about it.
Let’s get into it!
Study Overview
This large retrospective study analysed claims data from over 460,000 US adults newly prescribed GLP-1s between 2017-2022. The majority had type 2 diabetes (80.5%), obesity (44.9%), and were female (56.3%). Researchers tracked nutritional deficiencies for 12 months after starting GLP-1 therapy.
Key Findings
Deficiency Rates Are Substantial:
12.7% developed nutritional deficiencies within 6 months
22.4% developed deficiencies within 12 months
Vitamin D deficiency was most common (7.5% at 6 months, 13.6% at 12 months)
The Dietitian Paradox
Here's what's surprising: Patients who saw a dietitian within 6 months were more likely to be diagnosed with nutritional deficiencies:
18.5% vs 12.2% at 6 months
29.8% vs 21.8% at 12 months
The authors suggest this reflects increased screening and detection rather than dietitian care being harmful, patients referred to dietitians likely had higher baseline risk.
Comparison with Non-GLP-1 Users
When compared to matched patients taking only metformin, GLP-1 users showed higher rates of several deficiencies at 12 months, particularly:
Vitamin D deficiency
B vitamin deficiencies
Thiamine deficiency
Other interesting notes from the study
92% of patients hadn't seen a dietitian in the 6 months before starting GLP-1s
The average time to first dietitian visit was 128 days (over 4 months)
The authors note that GLP-1s can reduce energy intake by up to 39%, and also stress the importance of hydration monitoring (GLP-1s may suppress thirst).
B12 testing may be complicated by semaglutide interfering with assay results
Clinical Implications
This study starts to validate what we've observed in practice:
GLP-1s create predictable nutritional challenges that demand proactive, not reactive, intervention. With 1 in 5 patients developing deficiencies within a year, the current "wait and see" approach isn't serving our patients.
Next Steps
Build your referral case: Use this evidence to advocate for dietetic referrals at GLP-1 initiation. The 20% deficiency rate within 12 months provides data to support systematic referral protocols.
Strengthen monitoring protocols: This research reinforces the need for comprehensive baseline assessments and regular follow-up testing. Position yourself as the professional who catches these issues before they become problems.
Elevate your clinical narrative: Frame your services around preventing the documented nutritional complications, not just treating them after they occur. This shifts the conversation from optional to essential.
Read the full study here
Reference
Butsch, W.S., Sulo, S., Chang, A.T., Kim, J.A., Kerr, K.W., Williams, D.R., Hegazi, R., Panchalingam, T., Goates, S. and Heymsfield, S.B., 2025. Nutritional deficiencies and muscle loss in adults with type 2 diabetes using GLP-1 receptor agonists: A retrospective observational study. Obesity Pillars, 15, p.100186. doi: 10.1016/j.obpill.2025.100186.
Thanks for reading!
Leif
Got feedback? Email leif@glp1dietitianhub.com, I'd love to hear from you.
Note: This newsletter is for educational purposes only and should not be considered medical advice. Always consult a qualified healthcare professional for personalised guidance.
Subscribe for free to receive new posts and support my work