According to the Museum of Yo-Yo History, the famous toy can be traced back to 500 B.C. Greece. But the modern name "yo-yo" may come from the French word "joujou," meaning "little toy."

A 1789 painting shows a four-year-old Louis Charles, heir apparent to the French throne, playing with one. But neither young Louis nor his up-and-down toy likely came to a happy ending. That was the year the French Revolution started, eliminating the monarchy.

A new study shows that if your weight yo-yos up and down, you may be in for an unhappy ending too.

In a study published in the journal Circulation, researchers looked at data from almost 7 million healthy South Koreans with no history of heart attack, diabetes, high blood pressure, or elevated cholesterol.

Over seven years, they observed that folks whose weight, cholesterol, blood pressure, and glucose levels stayed consistent were far healthier than people whose levels went up and down and up and down, even as little as 5 percent.

And folks whose numbers varied the most (the top 25 percent) were 127 percent more likely to die early, 43 percent more likely to have a heart attack, and 41 percent more likely to have a stroke.

Bottom line: Avoid crash diets. The rebound weight gain can harm you.

Instead, aim for losing one pound a week, and gradually see your blood pressure, glucose levels, and bad LDL cholesterol decrease.

By maintaining consistency, you'll be able to enjoy variety in your workouts, meals, and the spice of life.