Are Patients On GLP-1s Getting the Right Nutrients?

As the use of glucagon-like peptide 1 receptor agonists (GLP-1 RAs) continues to exponentially expand obesity treatment, concerns have arisen regarding their impact on nutrition in people who take them.

While the medications’ dampening effects on appetite result in an average weight reduction ≥ 15%, they also pose a risk for malnutrition.

"It’s important to eat a balanced diet when taking these medications," Deena Adimoolam, MD, an endocrinologist based in New York City and a member of the national advisory committees for the Endocrine Society and the American Diabetes Association, told Medscape Medical News. "If someone’s diet is minimal, it’s important they’re keeping up with their need for macronutrients — protein, fat, carbohydrates — as well as micronutrients — vitamins and minerals."

The decreased caloric intake resulting from the use of GLP-1 RAs makes it essential for patients to consume nutrient-dense foods. Clinicians can help patients achieve a healthy diet by anticipating nutrition problems, advising them on recommended target ranges of nutrient intake, and referring them for appropriate counseling.

Where to Begin

The task begins with "setting the right expectations before the patient starts treatment," said Scott Isaacs, MD, president-elect of the American Association of Clinical Endocrinology.

To that end, it’s important to explain to patients how the medications affect appetite and how to adapt. GLP-1 RAs don’t completely turn off the appetite, and the effect at the beginning will likely be very mild, Isaacs told Medscape Medical News.

Some patients don’t notice a change for 2-3 months, although others see an effect sooner.

"Typically, people will notice that the main impact is on satiation, meaning they’ll fill up more quickly,” said Isaacs, who is an adjunct associate professor at Emory University School of Medicine, Atlanta. “It’s important to tell them to stop eating when they feel full because eating when full can increase the side effects, such as nausea, vomiting, diarrhea, and constipation."

A review article, written by lead author Jaime Almandoz, MD, University of Texas Southwestern Medical Center, Dallas, in Obesity offers a "5 A’s model" as a guide on how to begin discussing overweight or obesity with patients. This involves asking for permission to discuss weight and asking about food and vitamin/supplement intake; assessing the patient’s medical history and root causes of obesity, and conducting a physical examination; advising the patient regarding treatment options and reasonable expectations; agreeing on treatment and lifestyle goals; and assisting the patient to address challenges, referring them as needed to for additional support (eg, a dietitian), as well as arranging for follow-up.

Impact of GLP-1 RAs on Food Preferences

Besides reducing hunger and increasing satiety, GLP-1 RAs may affect food preferences, according to a research review published in the International Journal of Obesity. It cites a 2014 study that found that people taking GLP-1 RAs displayed decreased neuronal responses to images of food measured by functional magnetic resonance imaging in the areas of brain associated with appetite and reward. This might affect taste preferences and food intake.

Additionally, a 2023 study suggested that during the weight-loss phase of treatment (as opposed to the maintenance phase), patients may experience reduced cravings for dairy and starchy food, less desire to eat salty or spicy foods, and less difficulty controlling eating and resisting cravings.

"Altered food preferences, decreased food cravings, and reduced food intake may contribute to long-term weight loss," according to the research review. Tailored treatments focusing on the weight maintenance phase are needed, the authors wrote.

Are Patients Vulnerable to Malnutrition?

A recent review found that total caloric intake was reduced by 16%-39% in patients taking a GLP-1 RA or dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 RA, but few studies evaluated the composition of these patients’ diets. Research that examines the qualitative changes in macronutrient and micronutrient intake of patients on these medications is needed, the authors wrote.

They outlined several nutritional concerns, including whether GLP-1 RA or GIP/ GLP-1 RA use could result in protein intake insufficient for maintaining muscle strength, mass, and function or in inadequate dietary quality (ie, poor intake of micronutrients, fiber, and fluid).

"Although we don’t necessarily see ‘malnutrition’ in our practice, we do see patients who lose too much weight after months and months of treatment, patients who aren’t hungry and don’t eat all day and have one big meal at the end of the day because they don’t feel like eating, and people who continue to eat unhealthy foods," Isaacs said.

Some patients, however, have medical histories placing them at a greater risk for malnutrition. “Identification of these individuals may help prevent more serious nutritional and medical complications that might occur with decreased food intake associated with AOMs [anti-obesity medications],” Almandoz and colleagues noted in their review.

What Should Patients Eat?

Table. Nutritional Recommendations for Patients Being Treated with Anti-Obesity Medications
Dietary Component	Sources	Signs/Symptoms of Deficiency	Additional Considerations
Fluids	Water Low-calorie beverages Nutrient-dense beverages (eg, low-fat milk, soy milk) Limit sugar-sweetened beverages, alcohol, and caffeine	Hypotension Tachycardia Dizziness	Greater risk for dehydration in older individuals Low carbohydrate/ketogenic diets may increase dehydration risk
Energy	Healthy dietary pattern (vegetables, fruits, whole grains, lean protein, low-fat dairy/dairy alternatives, and healthy fats)	Reduced fat/lean mass Decreased strength/functional capacity	Aging is associated with decreased energy expenditure
Fiber	Whole grains Vegetables Beans, peas, and lentils Fruits Nuts and seeds Fiber supplementation if necessary	Constipation	Plant-based foods contain soluble and insoluble fiber
Protein	Beans, peas, and lentils Nuts, seeds, and soy products Seafood Lean meat and poultry Low-fat dairy foods Eggs Meal replacement products if intake from whole foods is insufficient	Loss of lean body mass Weakness Edema Hair loss Skin changes	Aging and acute illness are associated with increased protein requirements
Carbohydrates	Whole grains Fruits Vegetables Nuts and seeds Dairy foods Dairy alternatives	Low carbohydrate diets (ketogenic diets) may increase risk for dehydration, fatigue, halitosis, and other adverse events	Very low carbohydrate diets may lead to restricted intake of fruits, vegetable, and whole-grain foods, which are important sources of micronutrients and dietary fiber
Fats	Nuts and seeds Avocado Vegetable oils (limit palm and coconut oils) Fatty fish and seafood	Essential fatty acid deficiency (dry skin, hair loss, and impaired wound healing)	Adequate fat intake may promote gallbladder emptying (reduces risk for weight reduction–related cholestasis) Malabsorptive intestinal track disorders or history of malabsorptive bariatric surgery increases risk for deficiency of essential fats and fat-soluble vitamins Consumption of high-fat meals may cause gastric distress
Almandoz JP, Wadden TA, Tewksbury C, et al. Nutritional considerations with antiobesity medications. Obesity (Silver Spring). 2024; 32: 1613-1631. Source

Dietary and Behavioral Counseling

The drugs don’t necessarily motivate a person to eat healthier food, only to eat less food, Isaacs noted.

"The person might be eating low-volume but high-calorie food, such as bag of chips or a cookie instead of an apple," Isaacs said. Patients who are losing weight "may not realize that weight loss isn’t the only important outcome. Because they’re losing weight, they think it’s okay to eat junk food."

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Are Patients On GLP-1s Getting the Right Nutrients?