Can diet coke be useful for weight loss, or do the health risks out-way the benefits?
Diet drinks that are loaded with low calorie sweeteners (LCS) are thought to be just as bad as their sugary alternatives i.e. “full-fat” coke. (I still don’t get that term) as it’s purely sugar, not fat.
But the question is, is there any evidence to support this and what exactly does the research say about the effects diet coke and LCS (aspartame) have on health and weight management? Because it’s low in calories, can it be used to support weight loss?
Firstly, in order to lose weight you need to be in a calorie deficit, meaning you need to consume less energy than what you expend. For long-term success, you need to do this consistently. Immediately, the thought of swapping a 500ml bottle of Coke (200kcal; 50g sugar) for a 500ml bottle of Diet Coke (4kcal; 0g sugar) is much more appealing to help reduce calories. But what about the huge amounts of aspartame?!
What does the science say?
Aspartame has been linked to causing cancer, increasing weight and many other health issues, however the science doesn’t support this to be the case in humans.
In 2006 the US National Cancer Institute conducted a study of nearly half a million people, comparing those who consumed drinks containing aspartame with those who did not and found aspartame did not increase the risk of leukaemia, lymphoma or brain cancer. https://www.ncbi.nlm.nih.gov/pubmed/16985027
Rogers et al 2016 conducted a meta-analysis that showed the consumption of LCS improved weight loss in adults and children when compared to sugar based alternatives, as part of an ad libitum diet. https://www.ncbi.nlm.nih.gov/pubmed/26365102
Another meta-analysis in 2014 found no association between LCS and body weight or fat mass, and may have a positive association with BMI. The authors concluded that “data from RCTs, which provide the highest quality of evidence for examining the potentially causal effects of LCS intake, indicate that substituting LCS options for their regular-calorie versions results in a modest weight loss and may be a useful dietary tool to improve compliance with weight loss or weight maintenance plans.” https://www.ncbi.nlm.nih.gov/pubmed/24944060
More recently, Higgins et al 2018 in a RCT compared the effects of three daily aspartame doses (0, 350mg or 1050mg) for 12 weeks, to assess the effects each dose has on glycaemic control, appetite and weight management. https://www.ncbi.nlm.nih.gov/pubmed/29659969
Lets be clear on this…350mg aspartame is the equivalent to drinking 2 x 330ml cans of diet coke. So 1050mg equals 6 cans!!
The study showed that drinking 0, 2, or 6 (330ml) cans of diet coke per day for 12 weeks has no effects on glucose and insulin levels, appetite and ratings of hunger or body weight. HbA1c (marker of blood glucose levels), total cholesterol, HDL, LDL, and liver function were also no different between trials.
Take home messages:
Just to put this into perspective, this doesn’t make diet coke/soda a miracle cure for losing weight. There’s still absolutely no nutrititional value in soda drinks and therefore it is not recommeneded to start drinking 6 cans of diet coke per day. However, drinking the occasional can every now and again will not cause cancer or diabetes, but it can support weight loss.
– Drink water as much as possible throughout the day, but the odd can of coke will not harm you.
– If you like fizzy drinks but are trying to lose weight, swapping to diet versions can support weight loss.