They call it the “Baghdad bulge”. Standing outside a Burger King on the Camp Liberty military base near the city’s airport, a group of American soldiers ponder whether to order a second Whopper.

“Not me, man,” said Specialist Joe Lorenzo, “I put on so much goddam weight, who knows if my wife will recognise me when I get home?”

Now US troops have been withdrawn from Iraqi city streets and are spending more time behind barbed wire awaiting withdrawal, commanders are struggling to keep them entertained.

Offering ever-increasing food options is the first line of defence in the fight against boredom.

The favourite is lobster night at the D-Fac — American military vernacular for the official “dining facilities”. Thousands of sea creatures are regularly taken to the Iraqi desert by cargo plane.

For soldiers prepared to spend their own money on the base, there is also SG Village, an upmarket mall with restaurants clustered around a car park that opened three weeks ago. The most popular eatery is the red-walled Royal China, boasting a chef from Hong Kong who offers Szechuan-style chicken (£6.90), beef and green peppers (£7.80) and stir-fried noodles with vegetables (£4.20).

His uniformed customers sit on wooden deckchairs by a newly planted lawn. But SG Village faces competition from Camp Liberty Bazaar, where soldiers while away the day surrounded by branded American eateries such as Taco Bell, Subway and Popeyes Chicken and Biscuits.

Behind them is the Post Exchange, or PX, a military supermarket where they can buy T-bone steaks and pork loins along with a Smokey Joe Silver 14-inch barbecue grill (£16.70) and bags of charcoal (£2.80 for 7.2lb).

In the evenings, wisps of smoke rise from behind the soldiers’ housing containers and the surrounding concrete blast walls on what they call Echo Valley Road. “You make the best of the situation,” said Private Jonathan Roane, as he stirred embers with a pair of tongs. “We used to eat to fight. It’s not like that any more.”

When the barbecue is ready, he covers the grill with a giant carp with a greenish hue — which he caught in the artificial lake by the nearby al-Faw Palace.

Built for Saddam Hussein, it now houses the American high command, whose breakfast leftovers are dumped in the water every day to create a little angler’s paradise.

Sitting with his fishing rod among the reeds on the shoreline, one colonel said: “This is very different from my first tour in Iraq in 2005. We did some real soldiering then.”

Many of the 117,000 US troops here still conduct “red zone” operations, but usually now with Iraqi army soldiers, who are encouraged to take the lead in patrols.

The number of monthly US deaths has dropped from more than 100 two years ago to fewer than 20 now. But new dangers loom. Obesity is rising dramatically, according to a recent Pentagon report that called it “a significant military medical concern because it is associated with decreased military operational effectiveness”.

Since 2003, the number of overweight soldiers has doubled, with one in 20 now clinically obese.

Commanders are tackling the new enemy with an unusual array of measures. Rather than making soldiers run around the base in the midday heat, they offer them yoga classes, salsa dancing lessons, pedicures, book clubs, and karaoke nights to temper them. “They didn’t tell me about this at the recruiting station when I signed up,” said Specialist Ron Lopez.

“I mean, I expected many things going to war, but not this.”

A preoccupation for the soldiers in the coming weeks is preparation for Thanksgiving — the holiday on the fourth Thursday in November.

Colourful bunting and giant turkeys are already winging their way from America.

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