If you are taking Mounjaro or Wegovy, you may wonder whether fasting could help with weight loss. Many people try intermittent fasting (IF), where you eat only at certain times of the day.
However, GLP-1 medications naturally reduce appetite. This can make it harder to get enough energy, protein, and essential nutrients if fasting periods are too long. Your body still needs a balanced intake to support healthy weight loss and maintain overall wellbeing.
GLP-1 medications can help you eat less and support weight loss, but they do not replace the need for regular nutritious meals.
What is fasting and intermittent fasting?
Fasting means going without food for a period of time. Intermittent fasting (IF) focuses on when you eat, rather than what you eat. Common approaches include:
- 16:8 fasting: Eating during an 8-hour window and fasting for 16 hours
- 5:2 fasting: Eating normally 5 days a week and limiting energy intake (~500–600 kcal) on 2 non-consecutive days
Research shows that weight loss is mostly driven by total energy intake, not meal timing. A systematic review in adults who were overweight or with obesity found that when total energy intake was similar, intermittent fasting did not produce greater weight loss than standard calorie reduction (Harris et al., 2018).
This means fasting can help structure your eating if you find it useful, but it is not necessary to lose weight.
How GLP-1 medications affect appetite and eating
Mounjaro and Wegovy are GLP-1 receptor agonists. They support weight management by:
- Slowing stomach emptying, so you feel full longer
- Reducing appetite, which can naturally decrease food intake
- Helping maintain blood glucose levels
Because these medications lower appetite, long fasting periods may make it harder to consume enough protein and nutrients. Protein is particularly important for maintaining muscle mass, while vitamins and minerals support overall health.
It’s normal for your hunger to be reduced while taking GLP-1 medications. However, it’s still important to pay attention to your body’s signals and eat when your body needs energy, so you continue to meet your protein and nutrient needs.
Research shows that people taking GLP-1 medications often eat less overall, which may make it challenging to meet nutritional requirements unless meals are carefully planned (Johnson et al., 2025).
Tips for eating enough while taking GLP-1 medications
To stay nourished and maintain muscle and energy levels, it helps to:
- Include protein at every meal: eggs, yoghurt, fish, lean meat, beans, or tofu
- Eat nutrient-rich foods: vegetables, whole grains, legumes, nuts, seeds, and healthy fats like olive oil and avocado
- Have smaller, frequent meals or snacks: if large meals feel overwhelming, aim for 3 main meals plus 1–2 snacks
- Stay hydrated: water throughout the day is essential
- Listen to your body: dizziness, extreme fatigue, or fainting are signs to stop fasting and seek guidance
These tips support adequate energy and protein intake even if appetite is reduced. They also make it easier to manage hunger cues safely.
Fasting for religious reasons: Ramadan
Some people fast during Ramadan for religious reasons, abstaining from food and drink from sunrise to sunset.
Research in adults with type 2 diabetes suggests that GLP-1 receptor agonists can generally be used safely during Ramadan fasting when meals are carefully planned. A systematic review found that people using these medications during Ramadan had similar risks of side effects compared with other glucose-lowering treatments, and often experienced modest improvements in blood glucose control and weight (KamrulHasan et al., 2025).
Tips for safer fasting during Ramadan:
- Suhoor (pre-dawn meal): choose slow-digesting foods that release energy gradually, such as protein (eggs, yoghurt, beans, tofu), complex carbohydrates (oats, wholegrain bread and rice), and healthy fats (nuts, avocado, olive oil)
- Iftar (sunset meal): start with fluids and light foods, then enjoy a balanced meal with protein (fish, chicken, beans), plenty of vegetables, and whole grains. Avoid sugary or fried foods to prevent digestive discomfort
Planning nutrient-rich meals and staying hydrated is key to a safe fasting experience.
Key takeaways
- Weight loss is mostly about energy intake, not meal timing
- Strict intermittent fasting is not required to lose weight while on GLP-1 medications
- Appetite reduction is expected, but you will still feel hunger at times
- It’s important to respond to your body’s signals and eat when needed
- Eating enough protein and nutrients is essential for maintaining muscle and overall health
- GLP-1 medications support weight loss by reducing appetite, but they work best when combined with consistent, balanced nutrition
References
Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., Whittaker, V., Sharp, T., Lean, M., Hankey, C., & Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI database of systematic reviews and implementation reports, 16(2), 507–547. https://doi.org/10.11124/JBISRIR-2016-003248
Johnson, B., Milstead, M., Thomas, O., McGlasson, T., Green, L., Kreider, R., & Jones, R. (2025). Investigating nutrient intake during use of glucagon-like peptide-1 receptor agonist: a cross-sectional study. Frontiers in nutrition, 12, 1566498. https://doi.org/10.3389/fnut.2025.1566498
Kamrul-Hasan, A. B. M., Pappachan, J. M., Ashraf, H., Nagendra, L., Dutta, D., Kuchay, M. S., & Shaikh, S. (2025). Safety and efficacy of glucagon-like peptide-1 receptor agonists in individuals with type 2 diabetes mellitus fasting during Ramadan: a systematic review and meta-analysis. World journal of methodology, 15(4), 105478. https://doi.org/10.5662/wjm.v15.i4.105478
