Ultra processed foods hinder weight loss on Mounjaro, new study confirms
Tanya Reynard | Last update: 14th August 2025
If you’re on Mounjaro and still eating processed food, even the “healthy” kind, your results may be slower or short-lived. A new study confirms what SlimrChat members have suspected for a while: ultra processed foods could be sabotaging your progress.
TL;DR
- Ultra processed foods (UPFs) can limit weight loss — even on GLP-1 drugs like Mounjaro
- A new study found those who ate minimally processed foods lost twice as much weight
- Processed food can increase hunger, insulin spikes, and cravings
- Home cooking and whole ingredients are the most effective
- SlimrChat says: if you want the jab to work better, ditch the UPFs
Even on Mounjaro, ultra processed foods are a problem
A new study published in Nature Medicine followed two groups of adults over 6 weeks. Both groups were on calorie-controlled diets — but one group ate mostly minimally processed food while the other ate ultra processed foods (UPFs), including many so-called “healthy” items.
Despite similar calorie and protein intake, the group eating minimally processed foods lost twice as much weight as those eating UPFs — suggesting that it’s not just how much you eat, but what kind of food that makes the difference.
As Evie Whitehead, a highly qualified Registered Nutritional Therapist, told SlimrChat “While weight loss medications can reduce how much you eat, they do not change what you eat.”
🔗 Read the full study in Nature Medicine
What does this mean if you’re on Mounjaro?
Weight loss jabs like Mounjaro and Wegovy reduce appetite and help you eat less. But if you’re still eating heavily processed foods, especially those high in additives, emulsifiers, and sugars you may be working against the drugs, slowing your results and risking weight regain after stopping.
Evie Whitehead further explains, “These foods create spikes in hunger hormones and diminish the feeling of fullness, potentially undermining the appetite-suppressing effects of weight loss drugs…”
🔗 Read our guide: How processed foods can hold you back
What should you eat instead?
Focus on:
- Home-cooked meals using whole, fresh ingredients
- Foods with 5 ingredients or fewer
- Simple carbs like oats or sweet potato instead of cereal bars
- Healthy fats (olive oil, nuts, avocado)
- Plenty of water — not flavoured drinks or artificial sweeteners
Even if you’re not perfect, every swap counts.
Final word from SlimrChat
If you’re taking Mounjaro or another weight loss jab, cutting out ultra processed foods could double your results and improve your chances of keeping the weight off after the jab ends. This isn’t about being perfect, it’s about being aware.