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Key points
- 22% of GLP-1 patients develop nutritional deficiencies within 12 months, vitamin D being the most common.
- Standard multivitamins lack adequate doses of calcium, vitamin D, and potassium for GLP-1 patients’ needs.
- Patients regain 2/3 of weight within a year of stopping GLP-1s; medications don’t address root causes.
- Working with a registered dietitian improves outcomes through personalized meal plans and regular monitoring.
Co-written with Jenna Moore, RD, CSSD
As a psychiatrist, I’ve seen the mental health benefits that go along with successful weight loss—improved mood, enhanced self-esteem, and reduced anxiety. And as a registered dietitian, Jenna Moore has witnessed the physical benefits firsthand. Medicines such as semaglutide and tirzepatide have produced a breakthrough in the treatment of obesity. Patients generally lose 15-20% of their body weight. These medicines mimic the effects of a natural hormone called glucagon-like peptide-1(GLP-1) and are known as “GLP-1 agonists.” However, both of us have become increasingly concerned about a silent crisis that is developing behind these success stories: Malnutrition.
GLP-1 agonists work by causing us to feel full, delaying the release of food from our stomachs, and reducing our appetite. While this can produce impressive weight loss, it also creates a nutritional paradox. Recent studies have found that individuals using GLP-1 agonists reduce their caloric intake by 16-39%. This can result in some individuals consuming such a small number of calories that they are at risk of developing micronutrient insufficiency
From my psychiatric practice, I can tell you that caloric restriction doesn’t just affect your body—it also impacts your mental health. Some patients experience brain fog, difficulty concentrating, and trouble sleeping. What many people don’t realize is that these aren’t necessarily side effects of the GLP-1 agonists. They may be symptoms of a nutritional deficiency
From my dietitian’s perspective, the food choices people make on these medications often worsen the problem. When their appetite is severely suppressed, people tend to eat whatever sounds tolerable rather than what’s nutritionally optimal. This can lead to inadequate protein and micronutrient intake
Malnutrition Is Common
A study examining over 460,000 patients who were prescribed GLP-1 agonists found that 22% developed nutritional deficiencies within 12 months of starting treatment. Vitamin D deficiency was the most common, affecting 13% of patients within one year. But the deficiencies went far beyond a single vitamin—vitamin A, vitamin C, B vitamins, calcium, and zinc levels were also reduced
Physical symptoms of these nutritional deficiencies can include hair loss, fatigue, muscle weakness, and slow wound healing. As a psychiatrist, I recognize that these same deficiencies can also cause psychiatric symptoms like depression, anxiety, and cognitive impairment. All of these problems can originate from insufficient vitamins and minerals
Why Standard Multivitamins Fall Short
When discussing supplementation with patients, many assume that a standard multivitamin will fix the problem. Unfortunately, that’s rarely true. Most multivitamins are created for people who are eating 1,800-2,500 calories each day and a diet with a variety of different foods. Multivitamins typically contain large amounts of nutrients that are easily obtained from food, like B vitamins and vitamin C, but inadequate amounts of the nutrients GLP-1 patients need most
- What are healthy approaches to dieting?
- Take our Healthy Lifestyle Test
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One example is calcium. Adults typically need 1,000-1,200 mg daily, but most multivitamins contain only 200-300 mg because of the limited size of the pill. Similarly, the amount of vitamin D required to correct a deficiency is often more than 5,000 IU per day. Standard multivitamins contain only 400-800 IU. Potassium is another example. Important for cardiac and muscle functioning, potassium is almost never included in significant amounts in multivitamins. The average male needs 3,400 mg daily, but multivitamins typically contain none.
A Comprehensive Nutritional Strategy
Patients on GLP-1 agonists require a supplement protocol that goes way beyond a single pill. Here are some general recommendations:
Calcium and Vitamin D: We recommend a combination approach using both gummies and chelated supplements to achieve 1,000+ mg of calcium daily, paired with 5,000-7,500 IU of vitamin D3
Diet Essential Reads
Food Noise: Is the Chatter About the Wrong Things?
Diet Soda and the Brain
Protein: This is important for preserving muscle mass during rapid weight loss. We target 1.5 grams per kilogram of body weight daily. We also use forms of protein that don’t further suppress appetite, such as collagen peptides or hydrolyzed whey protein
Omega-3 Fatty Acids: Essential for brain health and inflammation regulation, these are often dramatically reduced when overall food intake drops
Electrolytes: Supplementation with potassium and magnesium is important in order to maintain proper muscle and cardiac functioning
Addressing Root Causes
From my psychiatric perspective, one of the most important questions is: What happens when the medication stops? Research demonstrates that patients regain about two-thirds of their lost weight within one year of stopping treatment with a GLP-1 agonist. A 2025 review found the average amount of weight regained after stopping semaglutide or tirzepatide is 20 pounds
Why? Because the medication doesn’t address the psychological and behavioral root causes of weight gain—stress eating, poor sleep hygiene, and inadequate coping mechanisms are just a few. As a psychiatrist, it is clear to me that an integrative approach is needed. We must work with our patients to identify and change their negative cognitive and behavioral patterns. It is also important to refer our patients to a registered dietician for help with their nutritional planning
Why You Need a Registered Dietitian
The data strongly supports what both of us see clinically: patients who work with registered dietitians while on GLP-1 therapy have better outcomes. Interestingly, a recent study found that nutrient deficiencies were more likely to be diagnosed in patients who saw a dietitian—not because dietitian visits caused deficiencies, but because these clinicians knew what to look for and test for
- Design personalized meal plans that maximize nutrient density within appetite constraints
- Recommend specific supplementation strategies based on individual lab values and dietary patterns
- Provide strategies to manage common GI side effects like nausea and constipation
- Build sustainable eating behaviors that persist after the medication is discontinued
Avoiding Weight Regain After GLP-1
GLP-1 agonists are a powerful tool for the treatment of obesity, but they are just that—a tool, not a complete solution. The evidence on nutritional deficiencies and weight regain tells us that if patients want to successfully maintain the weight loss they achieve on these medicines, they need an interdisciplinary approach
We encourage patients to look at GLP-1 therapy as an opportunity to change their relationship with food, build healthy habits, and look at the psychological factors that drive their eating behaviors—all while monitoring their diet to make sure they are getting the nutrition they need
Working with an RDN can help you establish sustainable, healthy eating habits while you are taking a GLP-1 agonist. This way, once you finish your GLP-1 treatment, you will have the skills you need to keep the weight off and make sure your weight loss is permanent
By utilizing targeted nutritional supplementation and paying attention to behavioral changes, you can achieve not just weight loss, but lasting physical and mental health.
Jenna Moore is a Performance Dietitian. She works with a variety of people, specializing in performance nutrition, weight loss, gut health, autoimmune disease and anti-inflammatory nutrition. On a personal level, Jenna is passionate about hiking, surfing, rock climbing, meditation and yoga
Facebook image: Anton Vierietin/
References
Berg, S., et al. (2025). Discontinuing glucagon-like peptide-1 receptor agonists and body habitus: A systematic review and meta-analysis. Obesity Reviews, 26(4), e13929
Butsch, W. S., Sulo, S., Chang, A. T., Kim, J. A., Kerr, K. W., Williams, D. R., Hegazi, R., Panchalingam, T., Goates, S., & 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, 100186
Christensen, S., Robinson, K., Thomas, S., & Williams, D. R. (2024). Dietary intake by patients taking GLP-1 and dual GIP/GLP-1 receptor agonists: a narrative review and discussion of research needs. Obesity Pillars, 11, 100121
Johnson, L., et al. (2025). Investigating nutrient intake during use of glucagon-like peptide-1 receptor agonist: A cross-sectional study. Frontiers in Nutrition, 12, 1566498
Mozaffarian, D., Agarwal, M., Aggarwal, M., Alexander, L., Apo. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Obesity Pillars, 100181
Wilding, J. P. H., Batterham, R. L., Calanna, S., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384, 989-1002
Wilding, J. P. H., Batterham, R. L., Davies, M., et al. (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism, 24(8), 1553-1564
