Shopping613 – if you feel you MUST drink cola, at least make it Diet Coke. I drink Diet Peach Snapple or water on Shabbos,and mostly water during the week. If you are trying to lose weight, water is your friend. Sugary cola is not. Not only is it a diuretic that dehydrates you (the caffeine does it), but it has absolutely no nutritional value.
When you load up regular cola, you are adding useless calories, when for the same money you could drink it sugar and CALORIE free. The taste IMO is better (or maybe I just got used to it). You might ask your family/friends to help you by cutting down on the amount of “way too much cola to ignore” that is around, and substituting either the diet drinks or water for some of it.
Try getting into water – it is so much better for you than soda. Vegetable juices (like V-8) are also low calorie AND have the added bonus of giving you some servings of vegetables and fiber, which is helpful to dieting. Fruit juices OTOH, are heavily loaded with calories, so though they are very healthful, it’s actually much better for you to just eat the piece of fruit, rather than drink the juice (though the juice is still better for you than cola).
In the end, this is your personal yetzer hara, and you need to find the way to overcome it on Shabbos (and every day). I speak from experience. Good luck.