How Ultra Processed Foods Impact Weight Loss

If you compare the way we eat today to how people ate a few decades ago, the difference is striking. Many of the foods we rely on now are far more processed than they used to be. While these foods are often convenient, when they’re eaten often, they can quietly get in the way of weight loss.

Let’s explore what ultra processed foods are and how they make losing weight harder, and how to reduce your intake of ultra processed foods.

What Are Ultra Processed Foods?

Ultra-processed foods are foods that have been significantly changed from their original form. They’re usually made using ingredients you wouldn’t typically find in your pantry at home, such as flavor enhancers, emulsifiers, colorings, sweeteners, and preservatives. Additionally, these foods are often high in refined carbohydrates, added fats, and added sugars.

A helpful way to think about them is to compare what the food started as to what it becomes. For example, corn turned into a sweetened breakfast cereal or potatoes turned into flavored chips. In each case, the original food is heavily modified through processing and the addition of ingredients that change how it’s eaten and how it affects the body.

A simple way to identify an ultra processed food is to look at the ingredient list. If it reads more like a chemistry experiment than a recipe, or includes ingredients you don’t recognize, it’s likely ultra-processed.

These foods aren’t “bad” or off-limits, but they can be an issue when they make up a large share of what you eat day to day.

How Ultra-Processed Foods Can Make Weight Loss Harder

Research consistently shows that diets higher in ultra-processed foods are linked with poorer health outcomes, including higher body weight, insulin resistance, inflammation, and changes in gut health (1). But what’s often more surprising is how strongly these foods can affect weight loss itself.

In a study where participants followed either a diet higher in minimally processed foods or one higher in ultra-processed foods (with both diets aligned to healthy eating guidelines and similar calorie targets), the group eating mostly minimally processed foods lost significantly more weight and body fat (2).

So why can eating more ultra-processed foods lead to such different weight loss outcomes? Let’s explore the main factors.

Ultra processed foods deliver more calories in less food

Ultra-processed foods tend to have a high energy density, which means they provide more calories per bite than less processed foods. This often means you can eat a meal that doesn’t actually seem like a lot of food, but it can still contain far more calories than expected. When many meals and snacks are built this way, staying in a calorie deficit requires more effort.

It’s also one of the reasons why these foods are the most important foods to track in the fatsecret app, as it helps you avoid underestimating your intake.

Ultra processed foods are easy to over-consume

Ultra-processed foods are designed to be highly appealing. Many are engineered to hit a specific combination of sweetness, saltiness, and fat that strongly activates reward pathways in the brain. This makes them easy to keep eating, even when physical hunger is already satisfied. In one study comparing ultra-processed and less processed diets, participants consumed significantly more calories and gained more weight when eating ultra-processed foods (3). What made this especially interesting was how this happened. Researchers observed that people ate these foods much faster and with less chewing, which made it easier to consume more energy in a short period of time.

Ultra processed foods interfere with appetite regulation

Ultra-processed foods can affect how full you feel after eating. Compared to less processed foods, they’re associated with lower levels of appetite hormones that help signal fullness. This is partly because these foods are often lower in fibre and easier to digest, which can make meals feel less satisfying and leave you hungry again sooner.

How to Eat Less Ultra Processed Foods

Because of their impact on appetite, calorie intake, and weight loss, making a conscious effort to reduce how often these foods show up can help with your progress.

A simple first step is simply becoming more aware of which foods in your diet are actually ultra-processed. Start paying attention to ingredient lists and identify foods with long lists of unfamiliar ingredients or multiple additives.

From there, focus on small, realistic swaps rather than trying to change everything at once. For example:

• If you usually have a sugary or highly processed cereal for breakfast, try swapping it for rolled oats, then add fruit or nuts for flavor.
• Instead of packaged snack bars, opt for yoghurt with fruit, nuts, or seeds.
• Swap flavored drinks or soft drinks for sparkling water with juice to add flavor.
• Choose simple bread options with fewer ingredients over heavily processed varieties.

Becoming more aware of where ultra-processed foods show up in your diet, and making a few simple swaps, can make a meaningful difference to both your calorie intake and how satisfied you feel after eating. If weight loss has felt harder than expected, looking at the type of foods you eat, not just the number of calories, can be a helpful place to start.

Key Takeaways

• Ultra-processed foods are now a big part of everyday eating, and they can quietly make weight loss harder, even if calories seem under control.
• It’s not just about calories, but how those calories are delivered. Ultra-processed foods pack more calories into smaller portions, making it easier to eat more than intended.
• These foods are easier to over-consume. Their texture, flavor combinations, and eating speed make it easier to take in more energy before you realize it.
• Ultra-processed foods tend to be less satisfying. Lower fibre content and faster digestion can mean you feel less full after eating and hungry again sooner.
• You don’t need to avoid them completely. Focusing on awareness and making a few simple swaps can shift the balance of your diet in a way that better supports fullness and weight loss.

References

1. Ultra-Processed Foods and Human Health: A Systematic Review and Meta-Analysis of Prospective Cohort Studies (2023). doi: 10.1016/j.advnut.2023.09.009
2. Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial (2025). doi: 10.1038/s41591-025-03842-0
3. Ultra-processed foods cause weight gain and increased energy intake associated with reduced chewing frequency: A randomized, open-label, crossover study (2024). doi: 10.1111/dom.15922