As long as it's in the figurative sense, nothing beats killing two birds with one stone.
Take Charity Miles, an app that donates money to charity whenever you exercise -- meaning you're not only helping yourself, you're also helping others.
Now comes Foodtweeks (Android|iOS), an app that donates money to charity whenever you cut calories. And it doesn't leave you guessing; it helps you make small changes to the foods you eat so the cutting is easy.
Take, for example, the Caramel Frappuccino I just ordered at Starbucks. The app suggested ordering it without whipped cream. After selecting that option and tapping Submit, I learned that I'd saved 80 calories.
Likewise, a trip to Wendy's revealed all kinds of "tweeks," like replacing the top bun with lettuce or ordering a sandwich without mayo. These are small changes, to be sure, but they're the kind that can add up. A dedicated user could probably drop a pound or two every month by making such simple changes.
Along the way, Foodtweeks tallies up your caloric "donations." Once you hit 600, the company donates a meal to a local food bank. And you can double and/or triple a single donation by sharing news of it on Facebook and/or Twitter.
There's also a Coupons section, but for the moment it's empty, at least for me. (I'm not sure if it's location-specific or simply not populated yet.)
You'll want to register for an account before you start "tweeking," otherwise you won't get credit for your donations. You can do this via an e-mail address and password or by linking your Facebook account.
Like Charity Miles, Foodtweeks is easy to integrate into your daily routine and effortlessly altruistic. All it takes is a few taps to help yourself while helping others. Win-win.