A while back, I was looking into adopting a child. I learned a lot of things along the way. For example, I learned that since I was single, I couldn't adopt from certain countries. Even more surprising: at the time, I probably wouldn't have qualified to adopt from South Korea because ... I was too heavy!

Weight is a factor in many aspects of our lives, chief among them health. If you're considerably overweight, you stand a greater chance of developing serious health ailments, such as Type II diabetes and cardiovascular disease. If you're considerably overweight, that will probably affect how you view yourself and how others view you -- and not in a good way. That kind of stuff isn't news to me, and it's probably not news to you.

But here's something new: A study by Richard V. Burkhauser and John Cawley of Cornell, from the University of Michigan Retirement Research Center, titled "The Importance of Objective Health Measures in Predicting Early Receipt of Social Security Benefits." The subtitle: "The Case of Fatness."

Here's a snippet of the abstract (you can read the entire report, in PDF format, here):

Theoretical models argue that poor health will contribute to early exit from the labor market and the decision to take early Social Security retirement benefits (Old-Age or OA benefits). ... We contribute to the empirical literature by using a more objective measure of health, fatness, to predict early receipt of OA benefits. ... Overall, our conclusion is that fatness and obesity are strong predictors of early receipt of OA benefits.

At the end of the report, they spell out what it all means: "The magnitude of our results suggest that the upward trend in obesity in the U.S. could actually result in a higher percentage of future old-age cohorts taking OA benefits at age 62 despite the reduced protection such benefits will provide."

A troubling combination
Got that? Americans, in general, have been getting fatter, meaning that more and more people may end up taking their Social Security benefits early. And that's kind of a big deal. Here's an example that can shed more light, taken from an actual Social Security report on a worker's estimated benefits:

  • At his current income level, if he stops working and starts receiving benefits at age 62, he can expect to receive around $1,215 per month.
  • If he waits until age 67 (his full retirement age), he can expect $1,774.
  • If he holds out until age 70, he stands to receive $2,210 monthly.

See? That's a huge difference.

Of course, though, we're each in a different situation. If you don't expect to live past 75, you might be better off opting for the earlier payout. Another factor is how much you have to live on, besides Social Security. If you don't have much, then you might have an extra incentive to keep working longer, to accumulate more money.

Don't get blindsided
One of the problems associated with many people's retirements is that they often get blindsided. They think they'll have enough money, but poof -- their former employer implodes in some way, or at least cuts back on retiree benefits. Or some health crisis ends up eating a huge chunk of their nest egg. Or they're laid off several years before they planned to retire.

You can't prevent every nasty surprise, but you can plan effectively enough to reduce them. Obviously, saving as much as you can, and beginning as early as possible, is one good way to start. And you should also focus on investing effectively and minimizing taxes. And now we learn one more reason why we might want to lose some weight as we approach our golden years -- to help us defer our retirement age, if we want to do so.

Investing for retirement
Here's one retirement planning tool that might be of interest to you. It might not offer the absolute best returns, but it can save you time and trouble. It's the target-date mutual fund. Each of these is designed around a specific retirement date, with its investments chosen accordingly. The Vanguard 2025 (VTTVX) fund, for example, is designed for those who plan to retire in 2025. It recently had 79% of its assets in stocks and 21% in bonds, whereas its Vanguard 2045 (VTIVX) counterpart had 90% in stocks and 10% in bonds. The fund takes care of shifting your assets as you get older -- it adds more bonds in later years.

Target-date funds tend to look to other funds in their family's lineup. The Vanguard 2025 fund, for example, recently had 61% of its assets in the Vanguard Total Stock Market Index (VTSMX) and 9% in Vanguard European Stock Index (VEURX) -- giving you both domestic and foreign equity exposure. While the former has shareholders invested in the likes of American International Group (NYSE:AIG), Procter & Gamble (NYSE:PG), and Coca-Cola (NYSE:KO), the latter invests in firms such as UBS (NYSE:UBS), AstraZeneca (NYSE:AZN), and Nokia (NYSE:NOK). Combined, these give you global diversification.

We want to help
Let us help you with your retirement planning, via our Rule Your Retirement newsletter service. It's prepared by Robert Brokamp, a smart and witty guy who distills what you really need to know into a manageable volume each month. A free trial will give you full access to all past issues and allow you to gain valuable tips and even read how some folks have retired early and well.

The following articles may also be of interest:

Here's to a happy retirement -- and put down that eclair!

Coca-Cola is an Inside Value recommendation.

Longtime contributor Selena Maranjian owns shares of Coca-Cola. The Motley Fool is Fools writing for Fools .