SAO PAULO, Nov 13 (Reuters) - Brazilian digital lender

Nubank's adjusted net profit more than doubled in the

third quarter from year earlier on a foreign-exchange neutral

basis, it said on Wednesday, beating analysts' estimates with

record returns.

Nubank, which is backed by Warren Buffett, reported an

adjusted net profit for the quarter ended in September of $592

million, above the $559 million expected by analysts polled by

LSEG.

Chief Financial Officer Guilherme Lago told Reuters that the

profitability increase was driven mainly by more active

customers and higher average revenue per active customer, while

costs of services and clients changed little.

Nubank's annualized non-adjusted return on equity, a gauge

of profitability, stood at a record 30%.

Nubank's credit portfolio increased some 47% year-on-year to

$20.9 billion, while the 90-day-plus default ratio for loans in

Brazil, its main business, came in at 7.2%, up from 6.1% a year

earlier and 7% in the second quarter.