With the increasing use of GLP-1 and dual GIP/GLP-1 receptor agonists for obesity and type 2 diabetes management, clinicians are observing substantial reductions in patients’ energy intake. But how do these medications affect overall dietary quality, including protein and micronutrient intake? This narrative review by Christensen et al. (2024) provides a comprehensive overview of current evidence—and highlights important gaps. 

Reduced Caloric Intake with GLP-1 Therapy: Evidence & Limitations

Across ten clinical studies, patients using GLP-1 or GIP/GLP-1 RAs showed a reduction in calorie intake of 16–39% compared to placebo. Most studies measured intake via standardized meals followed by ad libitum consumption, rather than using gold-standard methods like 24-hour recalls. Only four studies evaluated macronutrient intake, and results were inconsistent. Some found reduced intake of fat, carbohydrates, and protein, while others observed no significant differences between treatment and control groups.

Nutritional Oversight in GLP-1 Studies: A Missed Opportunity

Despite the clear impact on appetite and cravings, very few studies incorporated dietary counseling, and only two reported the involvement of a registered dietitian. This raises concerns, especially as protein intake may fall below levels needed to maintain muscle mass, and micronutrient intake—including fiber, vitamin D, calcium, and iron—may also be inadequate, particularly in individuals with obesity who already tend to consume suboptimal diets. 

Research Priorities in Nutrition and GLP-1 Therapy 

The authors emphasize the urgent need for new research to better understand: 

• How these medications alter dietary patterns and diet quality 

• Whether reduced protein intake contributes to muscle loss or sarcopenia 

• What nutritional guidance should be offered alongside pharmacotherapy 

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