I don't think the fuel load was the problem here, but rather the met forecast. I recall once having a destination forecast of about 3,000m, with a prob 20 of 1,500m. The alternate was CAVOK. We tanked fuel, so arrived with plenty, to find the vis below Cat 2 minima. We held for a while, continually monitoring the alternate weather, which was still CAVOK. Finally we got the required minima and made an approach, only for the RVR to drop again and having to go around. Alternate still CAVOK, so with the RVR OK again, we set up a second approach and once more had to throw it away. Downwind at the alternate the vis was 3,000m, turning to intercept the ILS it was 1,200m and once established it was 150m. Go around and ask for a very tight radar circuit, with a request that if we went around a second time it would be "direct to finals" at the only other airfield available. RVR again 150m when established, but just above Cat 2 minima by 1,000'. Just after landing the fuel low-level lights came on on both sides. I calculated that if we had gone around and flown directly to the other airfield we would have landed with min reserve (just). So, I don't think there is any criticism against the crew, but someone needs to look at the forecasting system in that part of the world. Having said that, if the weather regularly does this, then extra fuel would certainly be a good idea.