hi lisa,
i do not know to which studies that you refer, but most studies belong in the circular file, because they have pre-determined outcomes, when said information influences people's behavior. this is tremendously true in the field of nutrition.

one does not have the same energy levels on low-carb diets, as they do when using sugar. sugar is a wonderful nutrient for the body, IN ITS CORRECT PROPORTION. people have abused their bodies through their diets, by eating lots of junk food. low-carb diets have gone too far the other way. it is scary to me that there are people who believe in limiting the amount of carrots they eat, but intaking quite a bit of animal fat is okay. all carbohydrates are not the same. all fats are not the same. we need plenty of sugar along with our essential fats, and protein.

those people living to 100 today, would be those who should be living to 140. and i do not only mean living long, but living healthily. medicine/science allows people to exist longer, not necessarily LIVE longer.

in terms of how much fat, i have stated as a starting point, 2 tablespoons of safflower oil (75% omega6, which is 28 grams of fat, and about 240 calories.) protein (probably at least 100 grams for everyone, with many having higher requirements, because of size and other variables.) the rest should be fresh produce and whole grains, because it is in these foods where we get all our phyto-nutrients, as well as our sugar. but not processed twinkies and such. as much freshly grown produce as possible. this is the biggest mistake that low-carb diets make. they do not differentiate between the carbs. and i laugh whenever i hear that potatoes are to be avoided because they have a high glycemic index. one does not need to worry about glycemic index, but rather the types of carbs they are eating. if one limited oneself to fresh produce and whole grains as one's carbohydrate intake, this would be all one would need to do. you could toss the high glycemic index out the window.