2 weeks Ago By [email protected] (Almha Murphy)
Have you tried the viral “dirty Diet Coke”? TikTok’s latest fitness craze has seen influencers mixing low-calorie soda with protein shakes in order to create the perfect post-gym treat. But an expert has warned that it could actually be doing more harm than good. It’s fair to say Diet Coke is making a major comeback in 2025.
From Cosmopolitan declaring it this year’s “trendiest drink” to Trump’s new oval office ‘Diet Coke button' , the drink has been endorsed by scandalous politicians, tech CEOs and ‘It girls’ alike. Meanwhile in the UK, the drink’s sales grew by more than 2% in 2024, placing it as the nation’s fourth most popular soda. Now Gen Z have been incorporating the “guilt-free” refreshment into their workout routines.
On TikTok, some videos have accumulated millions of views mixing Diet Coke (or other sugar-free variations like Coke Zero) in with their favourite protein shake. The trend is purported to have started in Utah, and typically falls under different names like a “dirty Coke” or a “high protein Coke float”. The ratios of Diet Coke to milk typically vary, but the results are the same: a frothy cola-flavoured glass of protein-laden soda.
And while some videos simply contain people attempting to hop on the trend, it's also been picked up by fitness influencers. “Your new high protein treat is about to be Coke Zero mixed with chocolate milk,” begins one gym-fluencer, before proceeding to demonstrate his recipe. In his caption, the drink is advertised as having 30g of protein and just 150 calories, as well as being a way to "stay fuller for longer".
He also claims it “tastes legit like an ice cream float, but supports muscle growth”. Sounds too good to be true? It may well be. An expert from the fitness brand Stock UK has warned that not only is the viral drink not a great supplement for real protein, it can actually be harmful to your digestion.
Director of Stock UK Luke Forsyth states that due to its high acidity, the drink can cause severe bloating and digestive discomfort. This comes as a direct result of mixing the Diet Coke’s carbonation and artificial sweeteners with the dairy and caffeine in the protein. He explains: “If you are relying on pre-made protein shakes for your protein, you are likely ingesting more calories from the sugar it contains than the protein itself.
” He also points out that while Diet Coke is low in calories, that doesn’t make it healthy: “Certain drinks can also contain a lot of filler ingredients, which effectively counteracts the point of opting for a sugar free coke.” For example, to replicate the sweetness of regular Coke, the diet brand contains high levels of aspartame – a sweetener that has been labelled as a possible carcinogen by the World Health Organisation . Plus, while it lacks calories, it also lacks everything else.
There isn’t a lot of nutritional value in drinking Diet Coke compared to other high-sugar drinks like fruit juice or a smoothie. Instead of opting for the TikTok treat as a post workout snack, Luke instead recommends adding fruit to pre-made shakes if you want an extra hit of flavour. Alternatively, it’s also better to try intake protein from whole food sources, like lentils, seeds and legumes.
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