Cescau was formerly co-chairman with Antony Burgmans, who has now been given a non-executive role.
In a move to support innovation, the company has scrapped its executive committee and reduced its 11 business groups. Alan Rutherford, Unilever global media director, retains his position, while three directors in their late 50s have retired.
Sales and marketing will handled by three regional heads. The leaders of the food division and the home and personal care division will be responsible for brands and innovation.
However, the company did not shed much light on its future advertising strategy.
Cescau said that Unilever's five-year Path to Growth strategy from 1999 to 2004 had failed to deliver its growth targets.
"We wanted to be transparent. But in doing so we created a straitjacket for ourselves," Cescau said.
The changes came as the consumer goods giant reported a loss of €255m (£175.5m) for the fourth quarter, after taking €1.5bn in charges for write-downs and goodwill. The firm halved the value of its SlimFast acquisition, writing off €650m, which was less than expected, as net income last year dropped to €1.88bn.
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