Most people find that the side effects from metformin stop after one or two weeks provided they take the metformin with food and slowly increase the dose. Personly I happy to take the little help metformin gives me, a low carb diet gives me more help, but why choose when I can have both.
However, if I got the side effects of metformin and they affected the quality of my life for more then a week or two, I would have stopped the metformin. Also, remember that some people get on better with the slow release version, so if you get the side effect don't give up without talking to your GP first.
Some people can lose weight by just going low carb, other people have to do very low carb, yet other people have to control the amount of their food as well as the type of food. People who start with "very low carb", then slowly increase the carbs to find what their body can cope with, seem to do better than people who remove a few carbs as they are forced to from their diet.
Some people find that stopping all sugar and not eating anything that tastes sweet is required before they can control how much they eat.