We have almost identical % as the UK when it comes to overweight people. We aren't even in the top 20 for obese nations.
We aren't built around a fast food culture, there's plenty of other ways to gain weight. We have a high eating out culture which involves pub food and restaurants.
We are...
There's a reason why the Americans are one of the most obese nations on the planet. This is part of that reason.
Americans can provide such products/services because their nation is built around fast food.