We often see questions around why whole bananas are a Slimming World Free Food (foods that can be eaten freely to satisfy your appetite, with no weighing, measuring or counting), while mashed bananas have a Syn value (and can be enjoyed in measured amounts). As with everything we do, there’s a scientific, evidence-based reason, as our registered nutritionist Dr Sarah Bennett explains…
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Breaking down the science
Mashing, blending or puréeing food doesn’t change its calorie content (the calories are all still there – just mushier!). Slimming World’s healthy eating plan is based on much more than just calories, though, and blending food makes it much easier to consume. It’s less filling, too – so we’re left wanting more to satisfy our appetite, which can increase our calorie intake and lead to weight gain.
When fruit is enjoyed in its natural, whole form, it’s low in energy density (calories per gram), bulky and satiating (it helps fill you up). When it’s mashed, juiced or made into smoothies, those same calories lose their bulky, appetite-satisfying properties and slip down much more easily. For example, research has shown that apple juice is consumed 10 times faster than the equivalent number of whole apples, and has far less filling power.
The process of breaking down and absorbing food allows your digestive system to register that you’re full, while releasing hormones that send signals to the brain to tell you that you can stop eating. When food is already partially broken down for us – if it’s blended or juiced, for example – there’s less work for the body to do, meaning our satiety signals aren’t triggered as much. It also means the sugar that was once contained within the cell walls of the fruit is now ‘free’ so it’s absorbed into the blood quicker, which can also affect appetite and make us feel less full than we would’ve if we’d eaten the fruits in their whole form.
But it’ll be mashed up in my mouth?!
True – and that’s actually another reason why whole bananas are Free and mashed bananas aren’t. The process of feeling full starts long before food reaches the stomach – it begins when we first see and smell food and then, importantly, when we start to chew. Chewing is a significant step in a chain of events that ultimately leads to us feeling full and stopping eating. Among other things, it increases the release of those all-important hormones that tell us when we’ve had enough. Removing this step by mashing or puréeing food can impact how full it makes us feel.
Do all mashed foods have a Syn value?
No, we’re only referring to mashed, blended or juiced fruits. This is mainly due to their nutritional profile and how we most commonly consume them. They’re naturally higher in sugar than other foods we might mash, and are also more likely to be used as a snack, smoothie or as a dessert – adding additional calories on top of main meals.
(While tomatoes are technically a fruit, because they’re generally used in savoury dishes, we classify them as a Free vegetable in our healthy eating plan. They’re usually served as part of a filling main mean or side, and not generally used as a snack or dessert.)
Can you explain why soup is Free, but vegetable juice isn’t?
When vegetables are blended to make soup, they’re usually eaten as a meal rather than a quick drink between meals or in addition to a meal. The heat of the soup slows the speed at which we eat, too, and research shows this gives our body a chance to recognise we’re eating and feeling fuller – something that tends not to happen when we gulp down cold smoothies or juice. Blending soup also retains fibre (compared to juiced vegetables), which causes the stomach to expand more and adds filling power.
At Slimming World, we’re passionate about helping you to achieve and maintain your weight loss goals, while still enjoying the real food you love. Our expert teams are committed to understanding the full picture around food and weight loss – including the science of satiety and the psychology of slimming – to support you in getting real weight loss results that last.
Read more about the science behind the Slimming World plan
More for members: Check out So, why is mashed banana Synned? for an in-depth look at this hot topic
Go bananas!
No food is banned at Slimming World, so you can still enjoy mashed bananas within your daily Syn allowance and lose weight. Here’s a bunch of our favourite banana recipes:
Classic banana bread
Chocolate banana bread
Slimming World flapjacks
Strawberry and banana smoothie bowl
Slimming World pancakes