Life on the ocean waves has become a lot less healthy, according to the US Coast Guard, which believes that America's ever-expanding waistline threatens the safe running of every passenger vessel in the country.
Concerned that heavier occupants might cause commercial vessels to capsize or sink, officials have added almost two stone to the weight of the "average" person used to calculate how many people a ship is licensed to carry. In the past, stability tests have worked on the basis that the average man, woman or child who sets foot on board would weigh 160 pounds. Under the US Coast Guard's new rules, that has jumped to the more robust figure of 185 pounds.
The increase reflects data kept by the Centres for Disease Control and Prevention which believes that the average American male is now 194.7 pounds, while women tip the scales at 164.7 pounds. About a third of US adults are considered clinically obese.
For the owners of passenger vessels, the effect of the new laws, which took effect last month, has been to reduce capacity. In Washington State, where a fleet of large ferries connects Seattle with surrounding islands, a typical ship has seen its maximum number of occupants cut from 2,000 to 1,700. "It's all about safety," Coast Guard Lieutenant Kirk Beckman told reporters.
In Key Largo, Florida, the captain of Island Time, a dinner cruiser, said he could now cater to only 134 people, down from 153. In New York, ferries that carry commuters and sightseers have suffered a 15 per cent cut to their maximum capacity.
Despite the changes, the commercial fortunes of larger vessels are unlikely to be particularly badly affected by the new law, since such boats rarely tend to be filled. It is the captains of smaller ships, which often operate on thin margins, who may have most to lose.
The US Coast Guard's norms apply to any ocean-going boat which carries more than six customers. To that end, David McGowan, the owner of a fishing boat called Ms Magoo which has seen its capacity cut to 26 from 30, told the New York Times that its resale value had suffered a fall of about $100,000.
It may not be the last time that average weights are revised upwards, either. The girth of Americans continues to increase steadily, particularly in the South, where a cluster of states from Texas to Kentucky are suffering obesity rates approaching 40 per cent.
Since other nations aren't quite so rotund, some say the new rules discriminate against ships that fly the US flag in other parts of the world. A Coast Guard spokesman told the Miami Herald it had received complaints from the captain of a US-flagged ship based largely in the Far East. "He said Asians weigh less than you domestic Americans. He wanted to know why he should be constrained by how fat all the Americans got when he carried mostly Filipinos."