Yes it's true, most Forex/Futures traders lose money. Here are some sobering stats from 2011 for instance (see table below). As you can see, on average 75% of traders lose their money in 4 months or less. And after 6 months 95% of traders blow up their account (I will try to find the article).
The number would be better if traders trade things like index futures and not forex. currency war happened years ago. Now there is zero currency war !!!
80 to 95% of commodities traders lose money as well, and that includes trading financial Futures instruments like the S&P 500.
The more liquid and popular a market is, the higher the percentage of losers. The more niche, the more people make money until the asset gets liquid enough to make it worthwhile for sharks. Then a big guy comes, gobbles up everything and the losing rates shoot up to 95% again
Fortunately, these "sharks" leave large footprints that the astute retail trader can spot and profit from...
"Lets say some broker writes 80% lose money..." From what point is account/user considered a loser for the stats that brokers use in disclaimers? It could be conflict of interest , and beneficial for brokers to show better numbers. How can one know that the stats are accurate?
US and European laws now force brokers to disclose what percentage of their clients are losing money. These numbers are verified by independent auditors.
There was a very good post recently on www.telegraph.co.uk that said it was the people using leverage with a spread bettor that lost money. The traders who bet unleveraged made money. They used a spread bettor as it was tax free not for the leverage.
On average after 6 months only 5% of new trading accounts (FX and Futures) are still profitable (or barely breaking even).