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Have you seen that music video "We Are Hungry"? It isn't a famine-relief fundraiser featuring well-meaning pop stars. It's a musical complaint about the new, reduced-calorie public school lunch size made by students at Wallace County High School, in Sharon Springs, Kan. The video, set to the tune of Fun's hit song "We Are Young," has been viewed more than 500,000 times on YouTube.

The new rules, passed by Congress in 2010 to fight childhood obesity and promote health, took effect in August. High school cafeterias must serve twice as many fruits and vegetables as before, limit proteins and carbohydrates, and serve lunches containing 750 to 850 calories.

For an average high schooler, that means two baked fish nuggets, a cup of vegetables, half a cup of mashed potatoes, one whole-grain roll, and eight ounces of fat-free milk.

"850 calories is plenty for lunch and ought to tide a teenager over until after school," Marion Nestle, a professor of nutrition at New York University, told ABC News.

Secretary of Agriculture Tom Vilsack echoed this sentiment in an interview with ABC News, emphasizing the time-honored value of the after-school snack.

So what can you get for 850 calories or less? There are, of course, school lunches that adhere to the Department of Agriculture guidelines…but you can also squeeze in a Big Mac and more at the 850 calorie max. Check out some meal comparisons below and watch the full story on "20/20? online.

Fast Food:

McDonald's

• Big Mac (550)
• small fries (230)
• Diet Coke (0)
• 2 ketchup packets (30)
• small iced nonfat latte with sugar free vanilla syrup (40)

TOTAL: 850 calories

(according to company nutritional information)

KFC

• Original Recipe chicken breast (360)
• cole slaw (180)
• mashed potatoes with gravy (120)
• green beans (25)
• Diet Pepsi (0)
• oatmeal raisin cookie (150)

TOTAL: 835 calories

(according to company nutritional information)

Subway

• Six-inch Cold Cut Combo sandwich - includes 9-grain wheat bread, lettuce, tomatoes, onions, green peppers, and cucumbers (370)
• American cheese (40)
• mayonnaise (110)
• Baked Lay's chips (130)
• oatmeal raisin cookie (200)
• diet drink (0)

TOTAL: 850 calories

(according to company nutritional information)

Sample School Lunches:

Chicken Sandwich Meal

• Grilled chicken patty sandwich with whole grain hamburger bun
• 1/2 cup sweet potato fries
• 1/2 cup green beans
• 1/2 cup chilled pineapple with mandarin oranges
• 1/2 cup 100 percent apple juice
• 1 packet of light mayonnaise
• 1 packet of ketchup
• 8 oz of 1 percent or fat free milk

Corn Dog Meal

• 1 corn dog with whole grain breading
• 2/3 cup of baked beans
• 1/2 cup of fresh cucumber coins
• 2 packets of light ranch dressing
• 1 packet of ketchup
• 1 packet of mustard
• 1 cup of fresh red and green grapes
• 8 oz of fat free chocolate milk

Spaghetti With Meat Sauce

• 1 cup of spaghetti with meat sauce
• 1/2 cup of whole wheat pasta
• 1 whole wheat dinner roll
• 1/2 cup of steamed broccoli
• 1 1/2 cup of mixed green salad
• 1 packet of light salad dressing
• 1/2 cup of chilled apple sauce
• 1/2 cup of red Anjou pear
• 8 oz of fat free strawberry milk

(Courtesy sample high school menus at the Florida Department of Agriculture and Consumer Services.)