It’s a lazy person’s dream: shed lard just by lying down in a hot bath.

It sounds like the stuff of late-night infomercials that sell you specially formulated H20 to make pounds melt away. It’s also scientifically proven to work — not just by doctors, but English doctors with impressive accents.

The study comes from Loughborough University, where researchers set out to study “the effect of passive heating on heat shock protein 70 and interleukin-6” — or, in layman’s terms, the effect of immersion in a nice scalding tub is comparable to exercise.

Cycling burned more calories than sitting in the tub. But just lounging about shaping the bubbles into a beard for your rubber duck burned as many calories as a half-hour walk — 140, to be exact.

The study wasn’t some vast clinical experiment; only 12 men were observed. But Loughborough boffins say they’ll continue to investigate the healing powers of heat as well as its caloric impact.

In the meantime, don’t give up walking quite yet. And don’t do jumping jacks under a hot shower. All the data isn’t in, and you could slip.