In the name of clean and healthy eating, if you cannot have a scoop of your favorite ice-cream, what is the point!! Healthy living & fitness is not eating tasteless, bland food and only vegetables & fruits! You should enjoy it as well – only then it can be embraced as a lifestyle and thus for the long term! Well, it is possible to have occasional ice cream and still lose weight, get healthy, etc if done smartly.
1 serving of vanilla icecream (~100 gms) is roughly 200 calories – almost all of it coming from simple carbs (sugar) and some fat. Now that is equivalent to nearly 3 dosa calories. So, if you are having a serving of vanilla ice cream, skip 3 dosa or 4 idly or 140 gms of cooked rice from your diet..or may even adjust it in subsequent 2 meals. This is how your diet and eat within your calories in a smart & flexible way.
However, please note that this is done on the basis of equating total calories only and not in terms of the calorie composition (protein fat carbs ratio), the amount of other micronutrients (vitamins, minerals, etc), fiber and even the type of carbs (simple or complex carbs) in the food. Further, this kind of substitution is possible ONLY if you do not have any medical conditions such as diabetes, etc.