The United States Department of Agriculture's food guide pyramid and its successor, MyPyramid, have been helping Americans make healthy, balanced dietary decisions since 1992. Things haven't always been so triangular on the dietary front, though.

Long before we started getting our eating pointers in pyramid form, there was a much more circular way to plan our menus: the USDA's Basic 7 wheel. As you'll notice, things are just a wee bit different in this earlier version. Butter and fortified margarine are no longer thought of as one of the basic food groups, and it's likely that very few modern USDA posters feature the phrase "Eat Any Other Foods You Want."

So what gives with this weird-looking chart? Is it some sort of hoax? Not at all. It's a fascinating relic from World War II. At the dawn of the big clash, Americans weren't facing an obesity crisis. Instead, they had the complete opposite problem: they were undernourished!

With the U.S. on the brink of entering the war in 1941, a Selective Service study of a million potential soldiers uncovered a troubling fact: About one in seven potential candidates for military service suffered from "disabilities directly or indirectly related to nutrition." Americans just weren't eating the right foods to keep their motors running.

Eating right got even trickier when the U.S. actually entered the war. Widespread rationing made finding a square meal tougher than ever, so in April 1943 the USDA rolled out this "Basic 7" plan that would help keep civilians sufficiently nourished to keep the war effort going. In addition to posters like this, USDA workers traveled the country giving demonstrations on how to work the Basic 7 into a rationed diet.

Even after the war ended, the Basic 7 plan hung around until 1956, when it was replaced by a simplified "Basic Four" plan that advocated eating vegetables and fruit, meat, milk, and cereals and breads each day. The modern food pyramid we all know didn't catch on until 1992.