IzzieS, ketosis is a achieved by increasing
fats and limiting
carbohydrates - (primarily by not eating or greatly limiting sugar, refined carbohydrates, fruit, though berries are still okay for some, grains, starchy, root vegetables, and legumes while continuing to eat vegetables which provide nutrients and fiber and
protein such as meat, poultry, fish, eggs, and nuts). In addition, I believe carb intake needs to be less than 75 carbs a day. Eric Westman, M.D., who has a clinic for helping people lose weight starts his patients at 20 carbs a day. I personally eat probably 40-50 carbs a day.
Essentially, the brain and body alternates between using carbohydrates or fat for "fuel". Ketosis switches the body to "fat burning mode" and helps us lose weight by using stored fat from our body and our liver, for those of us who have fatty liver. This link provides more information...
http://www.dietdoctor.com/lose-weight-by-achieving-optimal-ketosis
To learn more about the low carb, high fat, moderate protein (LCHF) diet, join us on the Low-carb Diet Forum here...
http://www.diabetes.co.uk/forum/category/low-carb-diet-forum.18/ and begin exploring the Diet Doctor website here...
http://www.dietdoctor.com/ This is one of my favorite introductions to the LCHF diet...
Not sure if that adequately answers your question, but it's a start.