In studies, the average person who tries the Cordain Paleo diet sees their HDL go up, and both their triglycerides and LDL go down. The average person who tries a high saturated fat Atkins diet sees both their HDL and LDL go up and only their triglycerides go down.
Low fat diets can be effective for weight loss, metabolic syndrome and diabetes IF sugar, white flour, white rice and potatoes replaced with unrefined carbs. And low fat, high complex carbohydrate diets plus fish oil are even better than a high fat diet in reducing triglycerides.
http://www.ncbi.nlm.nih.gov/pubmed/20631323
