For a woman who has two daughters, ages 8 and 11, and a popularity index that is way up there, obesity–and in particular, childhood obesity–seems a logical place for the Mom-in-Chief to throw her weight.

Especially given the role of obesity in the national health-care crisis. Almost one-third of children and adolescents today are obese and overweight. In the past 30 years, obesity rates have tripled among adolescents and more than doubled in younger children. Obesity reportedly costs the U.S. some $150 billion annually in medical expenses.

The First Lady’s new campaign, which she announced at noon today with her trim husband standing beside her, is called Let’s Move. The website, letsmove.gov, has plenty of info to help people get fit and eat better. But the teeth of this campaign may come in the alignment with corporate partners.

For instance, Coca-Cola and PepsiCo , along with other beverage peddlers, have agreed to list calorie counts on the front of their packages, vending machines and fountain equipment by the end of 2012. (Good move.)

School food suppliers including Sodexho and Aramark have committed to cut the amount of sugar, fat and salt in meals, and also increase whole grains within five years. Over 10 years, they’ll double the amount of produce they serve. (I wonder: Why must this take 10 years?!)

Pro athletes from 12 leagues–the NFL, MLB, WNBA, and MLS, among them–will promote “60 Minutes of Play a Day” through sports clinics and public service announcements. Meanwhile, media giants like Walt Disney , NBC Universal , Viacom and Time Warner pledge to fight obesity via PSAs, special programming, and marketing. Watch for Warner Brothers’ Looney Tunes to be fightin’ lean.

And click here to see the PSA that Michelle Obama filmed for NBC Universal. It will begin airing across NBCU’s networks this March.

Now, as for tonight, please eat wisely and if you don’t run, at least walk.