The First Year Of GLP-1 Use Comes With This Hard-To-Detect Side Effect
GLP-1 medications have become one of the most talked-about tools in metabolic health. They curb appetite, help regulate blood sugar, and have shown real results for weight management, so much so that GLP-1 medications just got WHO backing for obesity treatment.
But as more people start these medications, some side effects are coming into light. A recent study published in The Journal of Nutrition1 found that people in their first year on GLP-1s may be falling short on several key nutrients, and most people don't see it coming.
GLP-1s, appetite & nutrition
GLP-1 receptor agonists work by slowing digestion and reducing appetite, which leads to lower overall food intake. For this study, researchers wanted to understand whether that reduction in eating was also affecting nutritional quality, and whether it mattered how long someone had been on the medication.
Using NHANES data collected between 2007 and 2020, they looked at adults with type 2 diabetes and divided them into three groups:
- Non-users (4,247 people)
- Short-term users (people on the medication for less than one year)
- Long-term users (people on the medication for one year or more).
They then compared each group's likelihood of meeting recommended daily intake levels for key nutrients.
Because this was a cross-sectional study (meaning it captured a single point in time rather than tracking people over months or years), the findings show an association between short-term GLP-1 use and lower nutrient intake, not a direct cause-and-effect relationship.
Short-term users were significantly less likely to hit daily targets for five nutrients
Compared to non-users, short-term GLP-1 users were significantly less likely to be meeting recommended daily intake levels for folate, iron, niacin, potassium, and vitamin B6. Long-term users, on the other hand, showed eating patterns that looked much more similar to people not on the medication at all, suggesting that over time, many people naturally adjust how they eat.
- For iron specifically, 63% of non-users were meeting their daily target, compared to just 27% of short-term users.
- For niacin, 57% of non-users were hitting the mark versus 26% of short-term users.
- Potassium showed the widest gap: 95% of non-users fell short, compared to 71% of short-term users, meaning even the non-user group struggles here, but short-term GLP-1 users struggle more.
Why the first year carries the biggest risk
Why is the first year of using these medications so different? GLP-1 medications reduce appetite significantly, which means people eat less overall. And when you eat less overall, you tend to eat less of everything, including the foods that supply key vitamins and minerals. GLP-1s are unique in how quickly and dramatically appetite can decrease, often faster than a person's ability to consciously shift toward more nutrient-dense foods.
Long-term users appeared to develop eating habits that more closely resembled people not on the medication, suggesting that many people naturally recalibrate over time, gravitating toward more nutrient-dense foods or settling into new meal rhythms. But that adaptation takes time, and the first year is when the gap is most pronounced.
It's also worth knowing that nutrition isn't the only thing to monitor in year one. Research suggests unexpected bone health effects from GLP-1 medications, and reduced movement on GLP-1s is another underreported concern. Staying on top of your nutrition fits into a broader picture of proactive care during this period.
How to close the nutrient gap in your first year on GLP-1s
If you're in your first year on a GLP-1 medication, a few proactive steps can make a real difference.
- Ask for a micronutrient panel: Request bloodwork that includes folate, iron (and ferritin, the stored form of iron), B6, B12, and potassium. This gives you a baseline and helps catch any shortfalls before they become symptomatic.
- Make every bite count: When appetite is suppressed, nutritional quality matters more than ever. Focus on foods that pack a lot of nutrition into a small volume, including leafy greens, legumes, eggs, lean proteins, and potassium-rich options like sweet potatoes and avocado. Building up your daily protein intake is a good place to start.
- Consider a multivitamin: A good multivitamin can help fill gaps, especially for B vitamins and iron. Many folks (especially women) would benefit from a multi that also contains iron, like this one). Talk to your doctor or a registered dietitian about what makes sense for you.
- Don't skip meals entirely: GLP-1s can make it easy to go long stretches without eating. Consistently skipping meals makes it much harder to hit your daily nutrient targets.
- Protect your muscle: Eating less on GLP-1s can lead to muscle loss if protein intake and strength training aren't prioritized. The GPS framework is a practical guide to maintaining muscle while on the medication.
- Work with a dietitian: A registered dietitian familiar with GLP-1 medications can help you build an eating plan that accounts for reduced appetite while still covering your nutritional needs.
The takeaway
This recent study found that short-term GLP-1 users are significantly less likely to be getting enough folate, iron, niacin, potassium, and vitamin B6, with the risk concentrated in the first year of use. The study was cross-sectional and the short-term user group was small, so more research is needed, but the signal is clear enough to act on.
Proactive monitoring, a focus on nutrient-dense eating, and a conversation with your doctor can go a long way toward closing that gap.