To me, it looks like the sustainable food movement is more welcoming than previous food movements in the U.S. (like haute cuisine).  The feature items of sustainable food, like locally-grown vegetables and grass-fed beef, are available at markets that are open to the public and well advertised, not hidden behind secret doors in a private club or in exclusive restaurants.

In addition, the movement is more about ingredients than technique.  Look at the menu at Chez Panisse, for example, a restaurant on the front line of sustainable dining.:   simple preparations of extremely high quality ingredients.  Dishes you could imagine producing at home, like salads, steaks, mashed potatoes, fruit compotes.  

On the subject of sugar:  also of importance in the sugar trade was the conversion of the raw material (cane) or the by-product (molasses) into rum.  Rum had the advantage of a high value to weight ratio, and was a key currency in the slave trade.  The story is told, among other places, in A History of the World in Six Glasses, by Tom Standage.

It's always seemed to me that ecology, health, and gastronomic enjoyment went hand in hand, long before I moved to an apartment just down the road from Chez Panisse. My mother had an enormous vegetable garden, cooked all of our meals at home, and took an interest in learning new recipes and adding a certain amount of culinary flair. Even on the many occasions when my family, farming a small acreage in North Dakota in the 1980s, was flat broke, we ate very, very well.

This is how I've come to understand food: it should be made at home, by hand, and shared with loved ones, and it should be grown locally and organically. Even as a busy graduate student, I still take the time to make a home-cooked meal almost every day. It's resting and reviving for my mind and body and a way to enjoyably spend time with my husband. We don't eat at restaurants much, and it's less an issue of money than that I can usually cook better. We buy our produce at the local farmers' market and only eat what's available in season. It is so worth it to wait until the end of July for that first tomato. Our bodies are healthier, the planet is healthier, and our marriage is healthier. Everybody wins.

A little misinformation here about the British diet: high tea is a regional thing, a fairly protein-heavy meal generally with potatoes, bacon, sausage etc. taken in the early evening and not to be confused with afternoon tea, which is all carbs.  And it's definitely a stretch to suggest that the average Brit ate a meat-rich diet before sugar became cheap in the nineteenth century.