Call me unimpressed
Every few weeks I'll see someone mention/promote some new documentary which promises to solve America's health and/or weight problems. These "documentaries" are all quite similar and follow a simple format:
Step one: Find several fat and unhealthy people who eat the "Standard American Diet".
Step two: Get them to eat a different diet and to exercise.
Step three: Incredibly, they lose weight and improve their overall health!
Step four: Profit.
The "different diet" varies a bit, from vegetarian to vegan to juicing to paleo to organic to raw foods to supplements and probably many others. In America and other "Western" countries, it's easy to find overweight and unhealthy people. The documentaries take a few of these as representatives, puts them on the diet du jour, and BAM: weight loss and improved health markers. Then people are supposed to take this as evidence of the power of the diet and jump on the band wagon.
The first problem I have with this is it's unscientific. There are no controls, few subjects, and the documentary style means it's subject to "selection bias" (they're enrolling people whom they suspect will do the best) and "publication bias" (they might not include people in the final cut who weren't helped or dropped out because it's too rigorous of a diet).
The next problem is the "Well, duh!" issue.
The "Standard American Diet" isn't based on the Food Pyramid, the Plate model, or any other government initiative. It is not based on recommendations from the Heart Association, Mayo Clinic, or even the Beef or Dairy Council. The "Standard American Diet" is based on eating whatever you want all day long. It's fast food burgers, fries, and a large Coke. It's super-sweet cereal or a couple bacon-cheese-biscuits for breakfast. It's cleaning your plate at Olive Garden or Applebee's. It's a plate with no vegetables. It's getting extra chips or bread. It's the 2000 calorie appetizer.
In short, the "Standard American Diet" has too much fat and sugar and simple carbohydrates, not enough vegetables, and quite simply too many calories. It's a terrible diet, and so comparatively almost anything else will shine.
So, if you take someone who overeats, is overweight, and is showing signs of diet-related health problems, and put them on a diet – any diet – they'll lose weight and improve health-wise. It certainly helps that the diets include lots of vegetables and don't include a lot of sugar, but come on, it's the massively reduced calorie budget that causes the dramatic weight loss seen. Long term, you'll need a balanced diet of vegetables, fruit, nuts, good proteins, etc, but short term, severe calorie restriction will bring dramatic results.
It's the inverse of Super Size Me. In that "documentary", the guy was a vegan, didn't overeat, and was in good physical shape. Then he ate nothing but giant sandwiches, giant deep-fried things, giant fries, and giant sodas for a month and, gasp, gained weight and felt bad. Was he expecting anything different from increasing his calories?
When I see someone promoting one of these films as proof that their particular diet ideology (or diedeology) is correct, it's quite frustrating, because yes: if you eat only 1000 calories a day in juiced vegetables you'll lose weight, but it's also true that if you eat only 1000 calories a day in steak and asparagus you'll lose weight, and the same goes for 1000 of junk food. The common idea here is to eat less food.