Oh what a tangled web we weave, When first we practice to deceive
If people consume more on imports, there might be a current deficit,whereas more money leaving the country than enter it, such as money spending on imports is more than exports.It certainly would cause economic growth. And i believe the expansion of production capacity is the main source of growth.When there is space for production capacity to increse to meets the AD,achieve new marcoeconomic equilibrium, thus economic growth.
Consumption leads to an increase in AD and so increase in output. However if there will be always rise in cosumption, suppliers might not reflect so fast because of scarce resources that are avialable and so this might lead to an inflation. And so economic growth will be achived only in a short run when there will be a rise in AD. While if increases investment, this means that more money is spent on capital goods which will create benefits in the future by increasing capacity utilisation. Thats why i agree with Chee and think that investment is the most important indicator of economic growth
It all depends whether we want to achieve growth in the short run or long run. In the short run consumption is vital in raising AD. However, in order to expand the capacity of the economy in the long run (LRAS) we need investment in order to increase the quantity and improve the quality of the factors of production.