Nutrition Tips for Patients Starting GLP-1 Therapy

GLP-1 receptor agonists like semaglutide and tirzepatide are changing the way we approach obesity. Some have even described them as a “medicinal version of bariatric surgery.” While these medications don’t interfere with nutrient absorption the way surgery does, they do dramatically reduce appetite. That means our patients need to be much more intentional about the foods they choose.

As clinicians, we get very little training about nutrition. That’s why I brought in dietitian Jen Cholewka, RD to talk to me on Primary Care RAP about caring for my patients on GLP-1 agonists–and why I want to share what I learned with you.

Starting With the Basics

When initiating a GLP-1, we always pair the prescription with some basic dietary advice. Many of these patients have already been working hard on healthy eating—cutting back on added sugars and building balanced plates. But once the medication kicks in and their overall food intake decreases, the traditional “half a plate of vegetables” model often doesn’t fit anymore. Instead, we should emphasize one central point: at every eating opportunity, no matter how small, make protein and fiber the priority.

Why Protein Matters

We know that weight loss, whether from medication or lifestyle alone, almost always comes with some loss of lean mass. The way to protect against this is adequate protein. How much protein, you ask? I asked the same.

One guideline is to eat 0.8 grams of protein per kilogram of body weight per day, (although some experts recommend more during weight loss). For a 100 kg (220 lb) patient, this translates to a daily target of at least 80 g per day, which is usually manageable if patients aim for 20 to 30 grams at each meal. Another way to frame it is that about 30 percent of total daily calories should come from protein.

Of course, appetite suppression can make hitting these numbers difficult. That’s where protein supplements can be helpful. Whey, soy, or pea-based shakes are often well tolerated, and for patients experiencing nausea, a shake may be easier to get down than a solid meal. When patients ask which shakes to choose, recommend options that deliver at least 20 grams of protein with fewer than 200 calories and minimal added sugar.

Fiber, Fat, and Balance

Fiber is equally important, both for satiety and for managing the constipation that often accompanies GLP-1 use. Women should aim for at least 25 grams daily of fiber and men for 35 grams, ideally from a mix of soluble and insoluble sources. Adequate hydration is key to making this work. Simple strategies—like adding chia seeds to yogurt or cereal—can boost intake significantly.

Fat intake is a bit more nuanced. Many patients come to GLP-1 therapy after following low-carb, high-fat diets, but they often find that large amounts of fat suddenly feel intolerable. Consider steering them toward a Mediterranean-style eating pattern instead, one that emphasizes monounsaturated fats, omega-3 fatty acids, and moderate portions. This approach supports cardiovascular health and glycemic control while being easier to maintain over the long term.

Counting macros isn’t necessary. Instead, encourage patients to stay mindful of their protein, fiber, and fluid intake. In practice, those three levers are the ones that make the biggest difference.

Micronutrients and Monitoring

Because patients are consuming less food overall, micronutrient gaps are common, though not as dramatic as in the bariatric surgery population. Consider recommending a daily multivitamin for everyone—it’s low risk and provides some insurance. Vitamin D deficiency is widespread, so it’s worth checking levels and supplementing if necessary. Calcium can also be considered if dietary intake is low.

Keep an eye out for symptoms of vitamin or mineral deficiencies. I had a patient who developed perioral paresthesias after significant weight loss on semaglutide. Her symptoms resolved once we finally added a B-complex vitamin, and I wish I had told her to start vitamins sooner. 

Consider checking a full micronutrient panel after a year on therapy, or sooner if symptoms arise. If the patient is losing weight faster than 1% of body weight per week, that would be another indicator that the patient is at risk for developing micronutrient deficiencies.

For labs, start with the basics—CBC, vitamin D, iron studies, and maybe prealbumin. If patients present with brittle nails, hair loss, diarrhea, or cognitive changes, expand the workup.

Managing Common Side Effects

Patients frequently complain of GI side effects while on semaglutide or tirzepatide: constipation, diarrhea, or just not wanting to eat at all. Our first-line recommendation should be food-based fiber and hydration. Whole fruits, vegetables, greens, and whole grains usually help, but if that isn’t enough, a fiber supplement can be added.

Appetite suppression is part of the goal of GLP-1 agonists, but sometimes these medications work almost too well. When patients report that they can barely eat, encourage them to try at least three small meals or snacks each day, even if portions are tiny (you could also consider reducing the dose of the medication, of course). The goal is to build habits they can sustain long term. If nausea or lack of appetite makes solid food unappealing, a protein shake may be the best option. It helps to remind patients to keep their kitchens stocked with nutrient-dense, easy-to-grab foods—string cheese, cut-up fruit and vegetables, or prepared leftovers—so that snacking feels less like a chore.

Fatigue is another common issue, and it can be multifactorial: too few calories, iron deficiency, or simply the medication itself. Patients should stay active during the day, drink plenty of water, and make sleep a priority. If symptoms persist, look more closely at labs.

Looking Ahead

One of the big unanswered questions with GLP-1 therapy is what happens when patients stop taking the medication. Weight regain is the rule rather than the exception, and in many cases, the regained weight is all fat rather than a mix of fat and lean mass. The best defense is proactive: encourage strength training and adequate protein from the very beginning so that patients preserve muscle while they lose weight. Those who build strong habits along the way are much better positioned to succeed when the medication is discontinued.

Should Every Patient See a Dietitian?

This is where I’ve shifted my own practice. In the past, I hesitated to push referrals because many patients had already seen a dietitian or nutritionist without much benefit. But GLP-1 therapy changes the playing field. These patients are suddenly free from “food noise,” which gives them a unique window to rebuild their eating patterns from scratch. Even one session with a dietitian early in therapy can make a huge difference.

I now frame it as an opportunity rather than a punishment. Dietitians are not the food police; they are partners in helping patients create habits that will keep the weight off long after the medication ends. With the growing availability of telehealth, access is also easier than it used to be.

To listen to my conversation with registered dietitian Jen Cholewka RD, on this topic, check out our episode, "GLP-1s and Nutrition Counseling" on Primary Care Reviews and Perspectives.