How GLP-1 Medications Affect Appetite, Eating Habits, And Nutritional Needs
GLP-1 receptor agonist medications (brands such as Ozempic, Wegovy, Zepbound, Mounjaro) have been shown to be very effective in promoting weight loss for many individuals. They increase the amount of glucagon-like peptide (and gastric inhibitory peptide, or GIP, in dual agonist medications such as Mounjaro) in the body. These are hormones that the body naturally produces, but in lower amounts.
GLP-1 medications primarily work by:
- Slowing stomach emptying, which can lead to nausea (experienced by up to 50% of individuals), vomiting, reflux, bloating, and constipation (up to 40% of individuals).
- Acting on the brain to signal satiety or fullness. A number of studies indicate they act on the part of the brain that is closely associated with the body’s reward system, which modulates urges and cravings. These two main mechanisms contribute to reduced food intake, which promotes weight loss. In some clinical trials, people who lost the most weight generally reduced their energy intake by 50% from baseline. It is also important to note that the rate of gastrointestinal adverse events listed above may decrease over time, but they don’t typically disappear altogether.
Because GLP-1 medications can be very effective at reducing cravings, appetite, and nutritional intake, there is the potential for individuals prescribed these drugs to have a higher risk for protein malnutrition (loss of lean mass), nutritional deficiencies, and dehydration compared to people losing weight with lifestyle interventions alone.
Why Working With A Registered Dietitian During GLP-1 Use Is Important
It is critical that individuals who are prescribed anti-obesity drugs also be prescribed nutritional guidance. In reality, most people are not receiving this guidance, which puts them at greater risk of inadequate nutrition, greater loss of lean mass, and often earlier discontinuation of these medications due to poorly managed side effects. More than 90% of individuals stop taking anti-obesity medications within a year, with many discontinuing after just six months.
A registered dietitian can provide guidance on the following:
- Tips to maximize nutritional density of food choices to prevent nutritional deficiencies when overall intake is significantly reduced
- Review protein needs to help minimize loss of muscle and bone tissue
- Suggest fluid and electrolyte consumption targets to prevent dehydration
- Provide suggestions on managing common GI side effects of GLP-1 medications
- Help individuals prevent or minimize weight regain, which commonly occurs when these drugs are tapered or discontinued
Many individuals who start GLP-1 medications may have concurrent medical issues such as diabetes, fatty liver disease, PMOS, obstructive sleep apnea, etc. A registered dietitian is educated in the medical nutritional management of these conditions. They are experts in assessing an individual’s medical history, medications, lab results, diet history, and social history to develop an appropriate nutritional care plan.
Should I Meet With A Registered Dietitian Before I Start A GLP-1?
Early response to GLP-1 medications predicts what people are going to do in the long run with their weight loss success. The average rate of weight loss is greater during the initial 12 weeks than it is in later stages. Working with a registered dietitian in the early or beginning stages (especially in the dose escalation phase) may help improve individual outcomes.
Meeting with a registered dietitian at Body Measure Inc. before commencing a GLP-1 medication can be helpful in setting realistic weight loss expectations and discussing changes in body composition that can occur while taking these medications (a DEXA body composition scan may be recommended to monitor these changes). The dietitian will review current eating patterns/preferences and identify potential nutrient gaps. A discussion of what types of foods to prioritize and keep on hand at home or how to make appropriate choices when eating out can also be helpful. Proactive strategies for managing potential side effects can lead to improved tolerance along with appropriate dosing recommendations by the prescribing clinician (these strategies can include both nutritional and/or pharmacological interventions).
Registered Dietitian Follow-Up For Long-Term Weight Maintenance
The efficacy of GLP-1 medications to produce weight loss is highly variable and individual. There is also no known method for stopping them without weight regain. Unfortunately, the slope of weight regain is often steeper than the slope of weight loss. Some studies have shown that a high protein, lower carb diet can help with weight maintenance once these medications have been discontinued (more research is needed in this area). It is also important to point out that the FDA approved GLP-1s for long-term chronic use without requiring the pharmaceutical companies to conduct enough studies. These are not necessarily reasons to avoid using these medications to assist with weight loss, but having an “off-ramping” plan is crucial for long-term success.
Working with a registered dietitian throughout your weight loss journey with GLP-1 medications can help you manage side effects, optimize your body composition, and help you achieve long-term maintenance. GLP-1s can be effective at promoting weight loss to help an individual meet their weight loss goal, but they do not address the deeper problem of an industry pushing a readily available supply of addictive, energy-dense foods. An experienced dietitian will provide you with strategies to help navigate the challenges of the addictive food environment that we all live in today.
Frequently Asked Questions About Meeting With A Dietitian Before GLP-1 Medication
What should I eat before and after starting GLP-1 treatment?
Everyone (whether they use a GLP-1 medication or not) should consume a protein-centric diet consisting of whole foods that also provide a good source of micronutrients (vitamins, minerals), fibre, and healthy fats. Drinking adequate fluids to meet hydration needs is also vital.
Will meeting with a dietitian help me avoid muscle loss while losing weight?
A registered dietitian can provide guidance on ensuring you are consuming adequate protein to prevent loss of muscle and bone tissue while losing weight. Engaging in resistance training is also critical to minimize or avoid loss of lean mass (cardio-type exercise does not have the same effect, especially for individuals on GLP-1 medications).
How is GLP-1 nutrition counselling different from a general diet plan?
GLP-1 medications can result in greater and much more rapid weight loss than lifestyle interventions alone (diet and exercise). They lead to a more profound reduction in appetite, serious GI side effects, and greater loss of lean mass. These are important considerations that necessitate a different nutritional care approach and plan. Contact Body Measure Inc. to learn about the benefits of nutrition counselling.
Get Personalized GLP-1 Nutrition Support From Body Measure Inc.
If you are looking for expertise and personalized support to improve your nutritional health before and during GLP-1 treatment, book an appointment with our Registered Dietitian who has over 30 years of evidence-based, clinical experience. Our primary focus is to help you develop a personalized road map to achieve results and sustainable metabolic health.
Angela Martens, RD has been a Registered Dietitian for over 34 years, completing her undergraduate degree in 1991 and clinical internship in 1992. She also holds a Bachelor of Physical Education degree. Angela joined Body Measure part-time in November 2021.
Angela brings a wealth of clinical experience spanning diverse settings, including four years as an outpatient dietitian in Thunder Bay, Ontario, four years at the Victoria General Hospital, and over two decades at Cancer Care Manitoba. She has developed deep expertise in personalized nutrition using DEXA scan data, metabolic syndrome management, carbohydrate restriction strategies, sports nutrition, and nutritional support for clients on GLP-1 medications.
Angela creates individualized nutrition plans based on each client’s unique metrics — including body composition, lean mass, and resting metabolic rate — to set precise goals for calories, protein, carbohydrates, and fats. Rather than prescribing rigid meal plans, she focuses on equipping clients with the tools and skills they need to make lasting changes. She helps men and women address a wide range of concerns, including weight management, insulin resistance, Type 2 diabetes, fatty liver disease, PCOS, IBS, menopause-related changes, and stress-driven eating.
Angela’s philosophy centres on shifting the focus away from the scale and toward meaningful health markers. Her goal is to help each client understand their body’s physiology and make informed decisions that support long-term health.