Slimming World has a number of rules when it comes to healthy eating, but one in particular has left people baffled – and a doctor has explained the science behind it
One Slimming World rule has left people confused for quite some time, but Dr Sarah Bennett, an expert nutritionist, has explained why they have this advice in place – stock photo(Image: )
It’s a fresh start to the year, and that means countless people are keen to lose any extra weight gained during the festive period. Of course, you’re brilliant exactly as you are, but if you fancy adopting healthier eating habits, programmes such as Slimming World have built a reputation for helping folk get back on course.
That said, in times gone by, slimmers have been left scratching their heads over one particular Slimming World guideline, which many have branded as ‘peculiar,’ whilst others insist it’s utterly baffling. Yet, a medical expert has shed light on the reasoning behind this controversial rule.
So what’s the rule in question?
It’s the banana rule. For anyone unfamiliar with Slimming World, certain foods are classed as ‘free’ – meaning you can tuck in without a second thought – and bananas fall into this category.
People have been confused by the rule for quite some time (Stock Image)(Image: Getty)
However, if you mash up a banana, you’ll need to count it towards your ‘syns’ allowance, despite the calorie content remaining identical, reports the Mirror.
Slimming World captioned their explainer video: “What’s the deal with mashed bananas? Dr Sarah Bennett, one of our expert nutritionists, is here to set the record straight”.
The clip kicked off with a flurry of bemused comments about the banana conundrum, including: “I can eat 20 bananas and not have to syn. But mash one and it’s five syns. Make it make sense” and “You don’t swallow a banana whole, you mash it with your mouth to swallow, so how does that work?”.
Dr Sarah Bennett clarified that whilst mashed and whole bananas contain identical calorie counts, there’s genuine scientific logic underpinning the healthy eating programme’s approach. She explained: “Mashed, blended, and juiced fruit goes down easier, and it has less volume, so it’s less filling. Also, the process of feeling full starts long before the food reaches our stomach.
“Chewing releases satiety hormones, as do the later stages of digestion. By mashing the banana, you reduce the impact of both of these steps, so you don’t feel as full. That’s when you might find yourself reaching for other snacks later”.
Dr Sarah Bennett clarified that as a Slimming World member, “you can still eat mashed banana,” emphasising that “nothing is banned”. However, she pointed out that “when it comes to weight loss, eating whole fruit has a bunch of benefits”.
A 2025 study investigating whether whole fruit or fruit juices were more beneficial for individuals revealed that “fruit consumed in solid form provides greater satiety due to delayed gastric emptying and related physiological reactions”.
The researchers also highlighted that the “synergistic effects of polyphenols and fibre in whole fruit benefit the gut microbiome by acting as prebiotics and producing short‐chain fatty acids that reduce inflammation”.
In summary, there are more “health benefits in whole fruit than fruit juice”.
A senior dietician at The British Heart Foundation added: “Whole fruits generally contain less sugar than foods like cake, biscuits and chocolate, and come without the added fat. Because of their water and fibre content, they will fill you up for relatively few calories.
“A medium banana, for example, contains less sugar than a standard 50g bar of milk chocolate and half the calories, making fruit a good swap for sweet treats.”
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