Burger King has spent $3m (£1.5m) shuttering restaurants and rescuing cash-strapped franchisees in Britain as it struggles to cope with the nation's waning appetite for its Whoppers.

Mounting concern about health and obesity among consumers in Britain has left Burger King struggling - although the Florida-based multinational yesterday said it was beginning to see signs of a recovery in UK sales.

The company closed 21 British outlets in the three months to March, reducing its presence to 578 locations. But an advertising campaign tied to new products such as an Aberdeen Angus burger pushed sales into positive territory over the last few months.

The fast food's chief executive John Chidsey said: "We continue to focus on the task in hand and we're confident we have the right people and the right strategy to turn the UK around."

He was speaking on a conference call with US analysts as the company announced a 70% rise in adjusted quarterly profits to $34m. One-off costs included $1m for the closures in Britain and $2m blamed on "franchisee distress".

Britain has more Burger King restaurants than any country except the US - but it ranks third in sales, lagging behind Germany.

Six months ago, the company warned that it was suffering in Britain from "perceptions about obesity and food-borne illness", which had invigorated competition from bakeries and sandwich shops.

Like its rival McDonald's, Burger King has added baguettes and salads to its menu but it has also courted controversy by promoting high-calorie Double Whopper burgers. In a recent interview, the company's head of north-west European operations, George Minardi, said people were fed up with the "nanny state" and insisted: "There is nothing wrong to partake in your love of a great burger."

An intensive advertising campaign under the slogan "Have it your way" has played in prominent media spots in Britain.