A regular can of coca cola contains 139 calories whilst the same sized can of Diet Coke / Coke Zero contains 0 calories. So why is it that many people believe drinking diet soft drinks will result in weight gain?

The Theory

The myth is borne from the theory that the taste of artificial sweeteners found in soft drinks cause your brain to signal the pancreas to release insulin in order to handle the impending sugar intake. However, when this sugar doesn’t turn up (we’ve just ingested artificial sweetener remember, not real-life sugar) it apparently confuses the body and messes with your metabolic processes and in the end will cause you to put on weight.

Granted, there are studies that have speculated an association between diet drinks and weight gain (e.g. a 9 year study on 749 participants) but it is important to remember with any study that association is not the same as causation. Just because you can link an effect to an outcome, it does not mean that it directly caused it. There are many other variables to consider. For example, it could be the unhealthy habits of the diet drinker that leads to weight gain as opposed to the diet drink itself.

Myth Busted

Why have we all believed or still believe that diet drinks make you fat? The media! Journalists bite down on a small piece of information and run away with it. Commentary on so called ‘scientific studies’ are speculative, misleading and often frequently inaccurate. There are plenty of studies that have shown zero effect of diet drinks on weight gain. In fact, a 12 week study found that those who drank diet drinks as part of a low-calorie diet lost more than those who only drank water on the same low-calorie diet.

These studies however, get little to no coverage. Let’s be honest ‘DIET DRINKS ARE MAKING YOU FAT’ is a better headline than ‘DIET DRINKS ARE OK’.

I am not saying that diet drinks cause you to lose weight but I believe they are a great tool for aiding fat loss. A calorie deficit is KEY to fat loss. If you consume more calories than you expend in a day then you will put on weight and if you eat less than you burn then you will lose weight. It is as simple as that. It is science and you can’t argue with science. If you’re an avid fizzy pop drinker and start by replacing those 3 cans a day with 3 cans of a diet drink, this alone will lead to you consuming 417 calories less a day. In a week that is 2,919 and in a month around 12.6k calories. Theoretically that is 3.6lbs of fat lost by doing nothing else than replacing full-fat coke with diet coke.

My Advice

Now before you start angrily typing in the comments box, I am not saying that you should be drinking 3 cans of diet drink a day. The aim would be to reduce that number over time as you would with any other type of artificial processed food or drink. But it all comes down to behavioural change. Not many people can go cold-turkey on something they have been doing for years. Telling a client they need to eat less, as well as cut out all soft drinks could push them over the edge and very quickly result in them binging, or worse, giving up completely. Stick with making small changes over time.

Diet drinks are also a great tool for anyone with a sweet tooth. I have never been a big fizzy drinker but when in a calorie deficit and craving something sweet I will head to the supermarket and get myself a bottle of Coke Zero (tastes tons better than Diet Coke). This satisfies said sweet tooth and stops me from going off course and consuming a whole packet of TimTams (Australia’s version of Penguins and my Achilles heel).

TLDR; Having the occasional diet drink, or even 1 a day, will not stop you from achieving your goals. Unless your goal is to put Coca Cola out of business – then you’re probably not helping.

Categories: Nutrition

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