How do sugar and fat trick the brain into wanting more food?

Have you ever tucked into fast food or a ready meal and felt famished just a few hours or even minutes later? Maybe you’ve reached for a couple of biscuits and suddenly realised you’ve eaten the whole pack.
It doesn’t make sense, does it? You’ve indulged in something packed with calories and potentially eaten a much higher volume of food too. Surely, you should be feeling satisfied and full for some time, not intensely hungry, and craving for more in minutes.
Know this: It’s not a sign of a lack of willpower.

Fatty and sugary foods can trick the body and the brain into wanting more and more. That’s why you often experience a grumbling tummy almost immediately after eating, perhaps with a side order of sluggishness and irritability too.


In one clinical trial, for example, volunteers who were given ultra-processed foods ate 500 calories a day more than when they were given unprocessed meals. They also each gained 2 lbs on average within a fortnight.


Here’s the thing though: fatty, sugary, ultra-processed foods are everywhere and due to their highly palatable nature, they can be a difficult thing to limit. (Clever marketing can also make them hard to spot.) 


It’s not all physical. In fact, that desire to keep eating is partly psychological. Let’s look at some of the science.


The science behind why you keep wanting more

Fatty and sugary foods actually alter our brain chemistry and motivate us to overconsume. When we eat for pleasure rather than eating for energy, we trigger the brain’s reward circuit.


In fact, some researchers say that sugary and fatty foods activate the brain’s reward system in much the same way that gambling and cocaine do. These foods trigger the release of the neurochemical dopamine that gives us an intense feeling of pleasure.


The more you overeat these fatty and sugary foods, the more you become desensitised to that feeling and need to eat more and more sugar and fat to recapture it. It’s the very reason so many of us say we can never stop at just one square of chocolate but need to eat the entire bar. Kinda scary, huh? Or perhaps it feels like a lightbulb moment. 


According to research, fatty and sugary foods trigger the brain’s reward system before they even enter our mouths. Just seeing something tasty – like a fizzy drink or a bag of crisps – is enough to get us excited.

(I for one can salivate just looking at sour sweets, anyone else?)


On the physical side, some researchers reason that ultra-processed foods make us hungrier because they’re typically lacking in protein, a macronutrient that contributes to satiety. Some may also contain a lot less fibre, which takes longer to digest, and therefore keeps you feeling fuller for longer.


Some researchers also suggest that ultra-processed foods are just so damn tasty that we scoff them down extra quickly, making us less full and meaning we’re likely to eat more.


Another theory? It could be related to your hormones. Remember that clinical trial we mentioned earlier? The experiment found that levels of the hunger hormone ghrelin decreased for volunteers on the unprocessed diet, while an appetite-suppressing hormone known as PYY went up.


The science may be complex, still evolving and require a level of nuance for individual circumstances. However, one thing is certainly clear: the satisfaction that comes with eating fatty and sugary foods is usually short-lived, and you’ll probably feel ravenous before too long*.


*You’re also likely to have gone on a blood sugar rollercoaster – check out this blog for more insight.


What’s the big deal?

We know what you might be thinking: What’s the harm? Is eating greasy chips, sugary doughnuts, or fatty takeaways now and again really so bad


Firstly, the problem is that eating ultra-processed foods can become habitual. Due to their addictive – and convenient – nature it’s easy, if you aren’t paying attention, for these foods to quickly form a large portion of your diet.


When consumed on the regular they also have a knock-on effect on your health. Ultra-processed foods are linked with an increased risk of obesity, metabolic syndrome, inflammation, anxiety, depression, and certain cancers.


Here’s the really concerning part: sugar and ultra-processed food intake in the UK has been described as “excessive”. One study found that over half the food eaten in the UK comes from ultra-processed products, while other data suggests that many of us are eating twice the daily recommended amount of sugar. Worryingly, 65% of children’s diets are made up of ultra-processed foods.


Know this: These facts and figures aren’t here to scare you. They aren’t here to shame you either. Rather, they give you the power to make more informed choices. They also act as a reminder that when we eat these kinds of foods we’re both physically and psychologically hardwired to act this way.


In other words, experiencing and giving in to cravings after eating ultra-processed food isn’t a reflection on you and your level of willpower. It’s simply how your body responds to these foods.


The good news is you can break this cycle by making a few healthy changes…


Making better choices

So what does all of this mean for the way you eat going forward? Do you need to give up fatty and sugary foods for good? 


Not completely, no. Unless you have an existing allergy or health condition that requires foods to be avoided we tend to encourage an 80/20 approach to food. Food provides information and tools for your body so you can live well so we want the majority (at least 80%) to be from nutrient-dense foods. That said, food is also about socialising and pleasure too. Heavily restricted diets can be negatively impactful on your relationship with food which we don’t encourage.


Instead, we advise making mindful choices about your diet and prioritising nutritious foods that energise you and keep you feeling full up. Eating this way has a compound effect. The more you eat healthy, whole foods the less you crave all the fatty and sugar-laden ultra-processed stuff, and eating well becomes easier and easier – because you feel good when you eat well!


The tricky part? It’s not always easy to tell what foods are ultra-processed. Dubious marketing claims and clever packaging can often convince us that certain foods are healthy when they are anything but.


If you’re unsure, check the label, and as a rule of thumb, limit or avoid foods that contain more than five ingredients or that cannot be replicated in your kitchen – that’s how you’ll have a pretty good idea on whether if it’s been ultra-processed or not.


Up for a challenge?

Take a look through your fridge and cupboards this week and decipher what foods in your home are ultra-processed. Have a think about how these foods make you feel.


It’s time to make some healthy swaps. Try replacing those ultra-processed items, whether it’s breakfast cereal bars, crisps, fizzy drinks, ready meals, or something else, with whole foods.


If you find that tricky, consider whether you’re eating for health or for pleasure, and choose accordingly.


With a few simple changes, you can begin crafting a diet that satiates and satisfies you – and crucially, doesn’t have you reaching for sugary, fatty treats moments after eating. That’s real food freedom!

Why not further your food freedom and finally get a personalised approach to nutrition and health.

Our clients are free from faddy diets and food cravings once they find out what food nourishes their bodies and balances their blood sugars.
Want to find out how to be free from food too?