It doesn’t appear to cause significant weight gain issues. This paper says the weight gain after 6 months (0.58 ± 2.63 kg) is similar to placebo (0.15 ± 2.33 kg). Even if the result was clinically significant, we’re talking less than a pound difference after 6 months. You can easily fluctuate that much within one day.
As far as personal experience goes, I didn’t notice any issues with weight when I was on it.