Good on you Ray, for telling others about sugar. Your 4 kg loss is actually really great! "healthy weight loss" is listed by dieticians and doctors as 0.5kg per week- on average: which means that some weeks there may be a gain, or no loss, but if you record it on a list or graph, it works out to be around 0.5 per week.
That means your 6 week should have got you about 3 kg lost. So, you did better than that. Let us know what other changes you've made which have helped you- like substitutes for sugar.
Dennise