How fast you'll abandon your New Year's resolutions

Here, too, ambitions matter — and they seem to be pretty high. A Gallup survey of 828 adults in November found that, on average, men said they would like to lose 11 pounds, while women said their ideal weight was 20 pounds lighter.

One way people “seriously try” is by going on a diet. As my colleague Emily Oster explained in October, the diet you choose can affect how much weight you successfully lose. A meta analysis by the Journal of the American Medical Association (JAMA) looked at the average weight of participants who took on a specific diet and compared them to those who didn’t. It found that after six months, the Atkins diet resulted in the highest average weight loss (22.3 pounds).

Even for those who do manage to lose weight, success can be short-lived. That same JAMA research found that after one year, those on the Atkins diet had regained eight of the pounds they had lost. A separate 2010 study of 1,869 overweight and obese individuals found that almost a third were able to lose 5 percent or more of their bodyweight. Among those individuals, 34 percent were able to maintain at least 75 percent of their weight loss over the next five years.