Guest blog by Lillian Craggs-Dino, DHA, RDN, LDN, FASMBS-IH Whether you're on a GLP-1 weight loss medication, have had metabolic and bariatric surgery, or are considering either option, one thing is certain: What you eat matters. This blog breaks down the key nutrition principles for both treatment paths, explains what side effects to watch for, and shows you what a healthy, sustainable eating plan actually looks like. Understanding Obesity as a Chronic Disease Obesity is a chronic, relapsing metabolic disease that requires long-term treatment strategies to manage effectively. This means it's not simply a matter of willpower or short-term dieting. Like other chronic conditions, it needs ongoing medical support and lifestyle management. Two of the most important tools available today are metabolic and bariatric surgery and medications known as GLP-1 receptor agonists (GLP-1s). Common GLP-1 medications include liraglutide (Saxenda®), semaglutide (Wegovy®, Ozempic®), and tirzepatide (Zepbound®, Mounjaro®), with newer options like retatrutide on the horizon. It is worth noting that not all weight loss medications are GLP-1s. Others, such as Orlistat, Phentermine, and combination drugs like Phentermine-Topiramate and Bupropion-Naltrexone, work through different mechanisms. Types of Weight Loss Procedures There are several surgical procedures used to treat obesity. The most commonly performed include: Vertical sleeve gastrectomy Gastric bypass Biliopancreatic diversion with duodenal switch (BPD/DS) Single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) In addition to traditional surgery, there are also nonsurgical, device-based options, such as the gastric balloon, transpyloric shuttle, endoscopic sleeve gastroplasty, and the vagal nerve stimulator. Regardless of which approach you take, the foundation for lasting success is the same: a healthy diet, a balanced lifestyle, and regular physical activity. Why Nutrition Matters for Bariatric Surgery and GLP-1 Medications One important gap exists in current practice today: Patients who are prescribed GLP-1 medications often don't go through the same level of preparation as those undergoing metabolic and bariatric surgery. Surgical patients typically complete thorough medical evaluations, nutrition assessments, and education programs before they are approved for surgery. While similar preparation is recommended for patients starting weight loss medications, it frequently doesn't happen. This matters because both bariatric surgery and GLP-1 medications come with specific nutritional requirements and potential risks. Without proper preparation and guidance, patients may not achieve the best long-term outcomes. The Nutritional Foundation for Healthy Weight Loss For anyone actively working toward weight loss, the nutritional foundation is similar regardless of the treatment path. A reduced-calorie diet should include: Adequate protein to preserve muscle mass Complex carbohydrates for sustained energy Healthy fats to support overall health Plenty of fluids to stay hydrated Vitamin and mineral supplements to prevent nutritional deficiencies The table below outlines the specific nutritional recommendations for both bariatric patients and those using GLP-1 medications. Table 1. Nutrition Recommendations for Metabolic and Bariatric Surgery and Medical Management with GLP-1s1,2 Treatment Protein Carbohydrates Hydration Vitamin & Mineral Supplements Diet Progression & Eating Tips Metabolic & bariatric surgery 1.5–2.0g/kg body weight per day Healthy complex carbs At least 1.5 liters/day Bariatric multivitamin, calcium, high iron, B-complex, vitamin D, B12 (optimize with 100mg vitamin B1 before surgery) Begin with liquids, then slowly advance to pureed/soft proteins. Goal: Regular, nutrient-dense, culturally appropriate diet. Fiber >21g/day, including resistant starches. GLP-1 medications At least 60g/day or up to 1.5g/kg body weight Healthy complex carbs 2–3 liters/day Complete age-appropriate multivitamin, vitamin D, calcium, B12 Start with a soft, bland diet and eat small meals to help manage nausea. Fiber >21g/day. Goal: Regular, nutrient-dense, culturally appropriate diet. Common Side Effects and How to Manage Them It's important to know that many of the side effects seen after bariatric surgery are also commonly experienced by people taking GLP-1 medications.1,2 These can include: Nausea Constipation Abdominal discomfort Dehydration Food intolerances The good news is that these side effects are manageable. Eating small, frequent meals, staying well hydrated, and following dietary recommendations by your care team can make a significant difference. The Role of Your Medical Team and Registered Dietitian Nutritionist Ongoing support from a qualified medical team, including a registered dietitian, is important. A dietitian can help you build a meal plan that meets your nutritional needs, reduces side effects, and supports long-term weight loss success. Patients can also take an active role in their own care by: Tracking what is eaten each day Noting any side effects and discussing them with the care team Monitoring weight regularly The Bottom Line: Sustainable Weight Loss Starts With Good Nutrition The goal of obesity treatment is sustainable, healthful weight loss, achieved through a nutrient-dense diet and lifestyle habits that support long-term success. If you have questions about your own nutrition plan, reach out to your care team. A registered dietitian who specializes in bariatric and weight loss medicine can provide personalized guidance wherever you are in your journey. References Almandoz JP et al. Obesity (Silver Spring). 2024;32(9):1613–1631. Mechanick JI et al. Surg Obes Relat Dis. 2020;16:175–247.