Earth gets heavier weights because of melting ice that occurs, so that the circumference of the Earth increases. This is due to the existence of global warming is often called Global Warming.
"Melting ice in Antarctica and Greenland to be the main drivers of the addition of water to the ocean volume and additional water is drawn toward the equator. This led to the addition at the widest circumference of our planet," the scientists said, as quoted by the Daily Mail, Friday (8 / 7 / 2011).

In fact, the Earth has 'Sliming down or to lose weight' after the ice age ended about 20 thousand years ago.

During periods of long-term geological reduction Earth's surface and atmospheric temperatures lead to heavy layer of ice is so big, so they changed shape. The crust and mantle produces a bulge in the middle. Actually the Earth is not completely round, the land at the North Pole a few miles closer to the earth's core, rather than land on the Equator.
It is believed to be the effect of reflection from the ice age that will lead to our planet becomes more rounded than a perfect sphere.

"Bulge on the Equator has shrunk less than one millimeter each year," according to National Geographic.
There's something else happened that is compensated (the shrinking of the thickness of the earth), "said John Wahr, a geophysicist at the University of Colorado.

Rate of ice melting in the Arctic and the South, currently totaling 382 billion tons of ice per year. This is what causes the weight of the Earth to be 'fatter'.(okezone)