As the number of people taking GLP-1 medications for diabetes or weight loss increases, more dietitians—including those who don’t specifically work in weight or diabetes management—will see these individuals in their offices or reaching out for consults. They may be seeking nutrition counseling related to their GLP-1 use, or they may simply have a different nutrition-related concern.
While some patients are prescribed these medications by providers or clinics that provide a comprehensive evaluation and follow-up, this is not always the case for those using GLP-1s for weight loss. Many users obtain these medications from online compounding pharmacies or other online vendors that don’t require direct communication with a clinician. The “microdosing” trend on social media encourages use of these medications for weight loss in individuals with a “normal” or even low BMI.1
There’s no research looking at the nutrition habits of free-living humans taking GLP-1s for weight loss—or for diabetes, for that matter—but anecdotally we know some people on these medications falsely believe that because they’re losing weight or managing their blood sugar, nutrition and physical activity don’t matter. That couldn’t be further from the truth. This is where dietitians in almost any area of clinical or private practice can put their nutrition science and behavior change skills to work.
Energy and Nutrient Intake
GLP-1 medications activate central pathways that ultimately reduce appetite, increase satiety and slow gastric emptying. One narrative review found that treatment with weight loss doses of GLP-1 (semaglutide, liraglutide) or GIP/GLP-1 (tirzepatide) medications reduced calorie intake by 16% to 39% compared with placebo, and a few of those studies found that people taking one of these drugs ate fewer high-fat foods.2 Data from the STEP 5 clinical trial for semaglutide for weight loss also found that people taking GLP-1 medications have fewer cravings for sweet, salty, or starchy foods, what some call a quieting of “food noise.”3
However, because these medications reduce appetite, some patients may find it difficult to consume adequate calories and nutrients. Some users report forgetting to eat, while others may view having almost no appetite as a benefit. This may be because they feel this will encourage more or faster weight loss. Or it may be because they have little time, energy, or interest for meal preparation, or experience decision fatigue when deciding what to eat—challenges that are not unique to clients taking a GLP-1.
If a patient or client is experiencing more severe gastrointestinal symptoms, especially nausea, this poses an additional barrier to adequate intake. Any of these factors can potentially lead to nutrient deficiencies, electrolyte abnormalities, and other signs of malnutrition.
Of note, in people who are genetically predisposed to eating disorders, the effects of energy restriction on the brain—especially when followed by weight loss and social praise that typically follows—can initiate the onset or perpetuation of restrictive eating disorders, including anorexia nervosa.1 Many eating disorder clinicians are seeing patients for whom GLP-1 medications are a trigger, a tool, or both.
Nutrient deficiencies are a common concern with significantly reduced energy intake, regardless of the reason or means. Of specific concern are the fat-soluble vitamins (A, D, E, K), vitamin B12, folate, thiamin, magnesium, potassium, calcium, iron, copper, zinc, and selenium.4 While it’s ideal to get nutrients from food, many people taking GLP-1 medications may also benefit from a quality multivitamin and multimineral supplement, and possibly supplemental calcium and vitamin D, to bridge any gaps. Women who plan to become pregnant at some point should talk to their doctor about their iron status and whether they would benefit from an iron supplement. Older adults generally benefit from taking supplemental vitamin B12.
The bottom line is that adequate energy intake is also important, regardless of what a client’s appetite is telling them. If calories drop too low to support the body’s functions, this can harm almost every organ system, including muscles, bones, reproductive organs, and the brain. The typical recommendation is that women consume 1,200 to 1,500 kcal and men consume 1,500 to 1,800 kcal per day while taking antiobesity medications.5
But because this calorie level is still low, it’s essential that patients pay attention to food quality, emphasizing fruits, vegetables, whole grains, lean protein foods, low-fat dairy or dairy alternatives, and healthy fats, while limiting foods that are high in saturated fat, sugar, or both. This dietary pattern—the Mediterranean diet and the DASH diet are two examples—has additional benefits for cardiovascular health and general health. Counseling clients to eat smaller, nutrient-rich meals more often can be helpful if they find it difficult to meet nutritional needs with three meals a day.
Even when eating a variety of nutritious foods each day, if a client is unable to meet the calorie minimums mentioned above, they should discuss this with talk their doctor, as they may need a lower dose.
Protein and Muscle Health
Along with consuming adequate energy and micronutrients, meeting protein recommendations helps protect muscle and bone during weight loss and maintenance. As early as the mid-40s, muscle mass and strength of even healthy, physically active adults begin to decline. Loss of muscle mass is also common with any rapid weight loss.6 Because taking GLP-1 medications can result in a degree of weight loss approaching that seen following bariatric surgery, researchers are finding that the risk of muscle loss is higher with GLP-1s than with older weight loss medications, especially in the early stages of treatment.7
A 2025 study estimated that, in the absence of a structured exercise program, 20% to 25% of weight loss in nonelderly men and about 10% to 15% of weight loss in nonelderly women consists of skeletal muscle.8 It’s estimated that percentage of weight loss from fat-free mass—which notably contains skeletal muscle as well as all other nonfat molecules in the body, including water—could be as high as 25% to 39% in people taking a GLP-1.7 Rapid weight loss can lead to sarcopenia, a progressive form of muscle loss that causes muscle weakness, but physical activity and adequate protein reduce this risk.9
A protein intake of 1.2 g/kg may be an appropriate target.10 You can help patients and clients reach this target by taking the following steps:
• Plan each meal around a high-quality protein source.
• Consume protein three or more separate times each day.
• Aim for 20 to 40 g of protein at each meal.
• Keep high-protein foods readily available for snacks.
• If experiencing early satiety, eat protein foods first.
Protein should ideally be paired with physical activity—including strength training—to reduce muscle loss or even to maintain or increase muscle. This appears to be particularly important for older adults, whose bodies have more difficulty building new muscle, even with adequate protein intake.11,12 As a further step to help protect muscle mass, some doctors are adjusting GLP-1 dosing to prevent rapid weight loss. For example, instead of automatically increasing the dose every four weeks, increasing it only when weight loss plateaus or cravings start to return. Research is also underway to develop drugs that may help reduce muscle loss in people taking GLP-1s.
Takeaways
While prescription medications play an important role in health for many individuals, they don’t replace the broad benefits of balanced, adequate nutrition and regular physical activity. The idea that a pill—or an injection—can do it all may be appealing to some patients and clients, dietitians play an essential role in preventing the downstream effects of inadequate energy, protein, and micronutrient intake.
— Carrie Dennett, MPH, RDN, is editor of Today’s Dietitian.
References
1. Banks A. GLP-1 receptor agonists and eating disorders—cause for concern. N Engl J Med. 2026;394(17):1665-1667.
2. Christensen S, Robinson K, Thomas S, Williams DR. Dietary intake by patients taking GLP-1 and dual GIP/GLP-1 receptor agonists: a narrative review and discussion of research needs. Obes Pillars. 2024;11:100121.
3. Wharton S, Batterham RL, Bhatta M, et al. Two-year effect of semaglutide 2.4 mg on control of eating in adults with overweight/obesity: STEP 5. Obesity (Silver Spring). 2023;31(3):703-715.
4. Wadden TA, Chao AM, Moore M, et al. The role of lifestyle modification with second-generation anti-obesity medications: comparisons, questions, and clinical opportunities. Curr Obes Rep. 2023;12(4):453-473.
5. Almandoz JP, Wadden TA, Tewksbury C, et al. Nutritional considerations with antiobesity medications. Obesity (Silver Spring). 2024;32(9):1613-1631.
6. Faria I, Samreen S, McTaggart L, Arentson-Lantz EJ, Murton AJ. The etiology of reduced muscle mass with surgical and pharmacological weight loss and the identification of potential countermeasures. Nutrients. 2024;17(1):132.
7. Prado CM, Phillips SM, Gonzalez MC, Heymsfield SB. Muscle matters: the effects of medically induced weight loss on skeletal muscle. Lancet Diabetes Endocrinol. 2024;12(11):785-787.
8. Heymsfield SB, Yang S, McCarthy C, et al. Proportion of caloric restriction-induced weight loss as skeletal muscle. Obesity (Silver Spring). 2024;32(1):32-40.
9. Caturano A, Amaro A, Berra CC, Conte C. Sarcopenic obesity and weight loss-induced muscle mass loss. Curr Opin Clin Nutr Metab Care. 2025;28(4):339-350.
10. Tinsley GM, Heymsfield SB. Fundamental body composition principles provide context for fat-free and skeletal muscle loss with GLP-1 RA treatments. J Endocr Soc. 2024;8(11):bvae164.
11. Smith GI, Commean PK, Reeds DN, Klein S, Mittendorfer B. Effect of protein supplementation during diet-induced weight loss on muscle mass and strength: a randomized controlled study. Obesity (Silver Spring). 2018;26(5):854-861.
12. Villareal DT, Aguirre L, Gurney AB, et al. Aerobic or resistance exercise, or both, in dieting obese older adults. N Engl J Med. 2017;376(20):1943-1955.