I’m dieting at the moment and I drink 500 ml Pepsi max a day (along with water/squash). I was just wondering if the Pepsi max could cause weight gain?
Not really a question TSR is going to be able to answer I'm afraid – the use of artificial sweeteners is quite a controversial topic in nutrition science and currently there isn't enough evidence to make proper conclusions. The WHO (World Health Organisation) advises against using non-sugar sweeteners. You'd probably be better off drinking something like water or milk instead of Pepsi Max
Remember that "low calorie" does not always equal "healthy"! Aim to eat a good balance of a variety of foods, consistently throughout the day, every day. Get enough carbohydrates (the body's preferred source of energy), proteins and fats, as well as plenty of vitamins and minerals (e.g. colourful fruit and veg).
And one more thing – is there actually any need for you to be "dieting"? What is your current weight, height, age?
From reading some of your previous posts, I think it's unlikely that you are "fat". If you're struggling with your eating or feelings around this subject, please speak to a GP or a similar medical professional and hopefully they'll be able to offer you some advice and guidance on living a healthy, happy life