Does more food labeling related to calories and nutrition make a difference? 

About one third of American kids and teens is overweight or obese, nearly triple the rate in 1963, making it a much bigger health concern than smoking or drug abuse. Meanwhile, a paper in the Journal of Public Health says obese kids are more likely to be paying attention to calorie information in restaurants.  40 percent of kids aged 9-18 read calorie information yet 33 percent are overweight.

What gives?

Various advocates blame their pet fundraising cause.  Obesity is blamed on economics - obesity has some overlap with poverty, though in other countries poverty overlaps with starvation - smoking by the mother gets blamed, as do lack of neighborhood parks - though people in the country, where they are surrounded by giant neighborhood parks called nature, tend to be more obese than urban people - while eating solid food too early, phthalates and, oh yes, genetics and epigenetics make the list in various groups as well.

If I left out your advocacy issue, please let me know in a comment. I am sure someone has also found a way to blame GMOs, vaccines and fracking as well.

It isn't that kids are dumb - though if they are we can blame that on air pollution - they are reading nutrition and calories labels, they just eat the stuff too often anyway.  Yet we have policymakers who want to insist it is an awareness issue.  The 2010 Affordable Care Act - Obamacare - requires restaurant chains to change all of their menus and post calorie information. Which young people will see. And apparently ignore.

Since the largest chains already do it, we already know it doesn't help, it is an intellectual placebo from people who engage in 'we must do something' deficit thinking about the public and are not spending their own money for the experiments. Instead of blaming corporations, we have to consider that people are going to rationalize their choices. Fat people underestimate the calories of the food they eat. It's fun for food activists to target McDonald's or create voodoo claims that spinach and wheat are opiates - but the people who underestimated calories the most were those in a Subway, which promotes itself as healthier than other fast food places. People want to believe they are eating healthy, that there is a miracle health shortcut they'll find on Dr. Oz or, if they are stuck being heavy, that it is genes, a 'condition', or that companies are engaged in conspiracies:

"So I Married An Axe Murderer" - Colonel Sanders gets called out.

Of course, part of the problem is we allow groups to pathologize everything - if you've ever been to a party where over the course of an evening someone declared 85% of the people there as having Asperger's, you know subjective social science is all the rage.  If something is a pathology but we want to make such behavior exculpatory, we blame a malevolent outside force, like Burger King.

The Journal of Public Health paper found that young people who were obese generally did read calorie information - too late, they are already there and they are not leaving - but that there was a decline by people who ate fast food twice a week or more.  Girls were 80% more likely than boys to read calorie information but while obese kids were about 70% more likely to read calorie information than those at normal weight, obese kids who ate fast food twice a week or more were 50% less likely to bother reading at all.

Here are the nuts and bolts details.  They did a fine job of outlining the parameters so there isn't much need for me to rewrite it:

a sample of 721 American youth aged 9 to 18 years through mail surveys in Autumn 2010. Respondents were asked, "When calorie information is available at a fast food/chain restaurant, how often does this information help you decide what to order?" They were also asked for their age, gender, height, weight, and how often they ate in fast food/chain restaurants.

The sample had a higher proportion of boys (56.4%) and a higher proportion of respondents were aged 12-14 years (32.2%). Most youth had a healthy weight as assessed by BMI (65.8%), while 13.3% were classified as obese. Of those who reported eating at fast food/chain restaurants, 65.6% reported going once a week or less, while 34.4% said they went two or more times a week. When asked about using calorie information when it was available, 42.4% of youth reported using it, while 57.6% reported never using it. Youth who reported they never eat at fast food or chain restaurants (about 8%) or who reported they never noticed calorie information (about 20%) were excluded from the analysis.

Results: heavy kids who eat out a lot are more likely to report reading calorie information than those eating there once a week or less. They just don't use it when actually eating.

Lead author Dr. Holly Wethington of the U.S. Centers for Disease Control and Prevention's Division of Nutrition, Physical Activity, and Obesity said in a statement, "Public health practitioners, school nutrition services, retailers, and other interested groups can consider implementing complementary education programs to improve youth's understanding of calorie information to hopefully make calorie labeling part of a successful weight management strategy."

Why not label spoons then?

Labeling does not force people to make smarter choices, nor do advertisements about exercise. Those may inspire parents but young people who want to eat junk food and not exercise are going to wait their parents out and hope they get bored.  Any parent who forces their child to go on a diet in the 21st century is going to get on the local news.

You just can't legislate choice and America has a lot of choices when it comes to food. As a country, we're rich enough to be fat. Luckily, we are also rich enough to pay to read labels and get free health care.

Citation: H. Wethington, L.M. Maynard, and H.M. Blanck, 'Use of calorie information at fast food and chain restaurants among US youth aged 9–18 years, 2010', J Public Health  May 22, 2013  doi: 10.1093/pubmed/fdt049 (open access)