Burmese pythons can get into cardiac shape just by eating. These snakes typically go weeks to months without food. Once they swallow their prey, they boost their metabolism to digest the meal by temporarily making fresh heart muscle. Their cardiac growth is the fastest ever measured, reports a team from the University of California at Irvine in a study of 18 pythons.

Size of (rat) meal, as a percent of python mass: 25

Mass of heart when fasting, in grams: 0.95

Mass when digesting: 1.34

Percent increase: 41

Time of increase: 2 days

Increase in metabolic rate: up to 40-fold

Days to digest a meal: 14

SOURCE: Nature March 3